“Merging COACHING with SPORT SCIENCE & MEDICINE”
HIGH PERFORMANCE
SIRCuit
Haut niveau
“La fusion d’entrainement avec les sciences du sport et la médecine du sport” Fall / automne 2010
Volume 1 (2)
CAROL HUYNH
Gold in Beijing and Delhi!! l’or à Beijing et à Delhi !!
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SIRCuit Volume 1 (2) Fall / automne 2010
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SIRCuit Volume 1 (2) Fall / automne 2010
I am not a tech guy, yet somehow I see this catching on…. Lots of potential and now no excuse for not being up to date within High Performance. Marc Bowles, ChPC, Performance Planner Canadian Sport Centre Pacific
Thanks very much for forwarding me the preview of High Performance SIRcuit….it is very well done!! Excellent information and delivery format. Vicki Harber, Faculty of Physical Education & Recreation University of Alberta
Congratulations on this communication tool to share the knowledge. I am excited to see future issues and maybe be involved to share my knowledge with others across Canada. I am extremely excited to see the video links for the reader. This is a great feature!!! Pro Stergiou, Director of Biomechanics and Performance Analysis Canadian Sport Centre Calgary HP SIRCuit is partially funded by
Editor Creative Director Design team Content Director Contributing Editor
Debra Gassewitz David Roberts Kim Sparling Liz McDonald Nancy Rebel Dr. Jon Kolb, OTP
Contributors
Pro Stergiou Gordon Sleivert Jonathan Tremblay
Sport Information Resource Centre (SIRC) is Canada’s national sport library, established over 35 years ago. Centre de documentation pour le sport est la bibliothèque nationale du sport au Canada fondée il y a plus de 35 ans. Mailing address: SIRC 180 rue Elgin Street, suite 1400 Ottawa, Ontario, Canada K2P 2K3 Tel: +1 (613) 231-7472 Fax: +1 (613) 231-3739 Disclaimer: Author’s opinions expressed in the articles are not necessarily those of SIRCuit, its publisher, the Editor, or the Editorial Board. SIRC makes no representations or warranties whatsoever as to the accuracy, completeness or suitability for any purpose of the content. Avis de non-responsabilité: les opinions exprimées dans ces articles n’engagent ni SIRCuit, ni l’éditeur, ni le distributeur, ni le comité de rédaction. Le SIRC ne donne aucune garantie ni ne fait aucune déclaration quant à la qualité, à l’exactitude ou au caractère exhaustif de son contenu. Copyright © 2010 SIRC. All rights reserved. No part of the publication may be reproduced, stored, transmitted, or disseminated, in any form, or by any means, without prior written permission from SIRC, to whom all requests to reproduce copyright material should be directed, in writing. © 2010 SIRC. Tous droits réservés. La reproduction, le remisage, la transmission ou la diffusion en tout ou en partie de cet article sous quelque format que ce soit est interdit sans avoir obtenu au préalable la permission écrite du SIRC. Les demandes de reproduction de tout document protégé par droit d’auteur doivent être adressées par écrit au SIRC.
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Editorial Coaches love to learn! We launched the first issue of High Performance SIRCuit in May 2010, and across the country the response to the new and innovative communication tool was amazing.Your feedback was instrumental in encouraging the creation of this second issue and we thank you for your suggestions. SIRC and Own the Podium are continuing to build a tool that we hope helps you maximize your learning experience through targeted articles, podcasts, video and imagery. In this issue, we consulted with Dr. Jon Kolb, Director of Sport Science, Medicine and Technology, Own the Podium, the National Sport Science Medical Advisory Council (NSMAC) and the experts at SIRC to find and write articles that will assist our high performance coaches in the areas of sport innovation, proactive and preventative medicine and performance. Special thanks to our contributors, Pro Stergiou, Gord Sleivert, and Jonathan Tremblay, who worked diligently with our Creative Director, David Roberts, to provide video footage to enhance their articles for this issue and to clearly illustrate the concepts. In closing, we thought we would share some of your comments and encourage you to continue sharing the knowledge as we help our athletes to achieve excellence. Best wishes, Debra Gassewitz President & CEO SIRC What a great start! Alex Gardiner (athletics)
If Issue Number 1 is any indication – WOW – this is first class. Dave Pym, Managing Director Canadian Snowsports Association
Great work on this. Congratulations. We look forward to continuing the partnership.
Alex Baumann, Chief Executive Officer Own the Podium
Contents
Performance Performance 4 10
Performance Analysis Beat the Heat
Sport Innovation 18 19 20
Combining Hypoxic Methods for Peak Performance New Horizons for the Methodology and Physiology of Training Periodization The International Olympic Committee (IOC) Consensus Statement on Periodical Health Evaluation of Elite Athletes, March 2009
Competitive Intelligence 22
Coaching Stress: Causes, Costs and Coping
Proactive & Preventative Medicine 26
Récupération à court terme à l’aide des boissons énergétiques
Departments 21 24 25
Upcoming Events From the SIRC Collection Ask SIRC 3
SIRCuit Volume 1 (2) Fall / automne 2010
Performance Performance Analysis Integration of technologies for the assessment and improvement of athlete performances by Pro Stergiou Director of Biomechanics and Performance Analysis Canadian Sport Centre - Calgary
For Pro Stergiou’s bio
CLICK HERE
Abstract Technology for the assessment of athlete performances is being used on a daily basis in high performance sport. The use of video camera and computer software technologies have become readily available to coaches and are being used to assess athlete techniques/skills and make corrections to optimize performances. Also, the use of other technologies to measure forces exerted on or by the athletes are being used by coaches and researchers to try and gain some more insight on factors associated with good performance. The integration of technologies (video and force) into one easy to use package, that is available to the coach, for the on-site assessment of performances is a next step in the providing tools for the collection of information on athlete performances. Additionally, understanding the information that is coming from such technologies and how it can be used to assess and improve performance is important. This article will discuss and describe the integration of technologies used with elite Canadian athletes for the assessments of their performance (skills). Practical examples will be provided for the Olympic sport of Luge and the Paralympic sport of swimming, showing how integration of technologies have been implemented into on-site training environments to provide real-time information for the improvements of performances.
Résumé La technologie pour l’évaluation des performances des athlètes est utiliser sure une base quotidienne dans le sport de haute performance. L’utilisation d’une caméra vidéo et des technologies de logiciels se sont facilement disponible pour les entraîneurs et sont utilisés pour évaluer les techniques et compétences des athlètes et faire les corrections pour optimiser les performances. En autre, l’utilisation d’autres technologies pour mesurer les forces exercées sur ou par les athlètes sont utilisés par les entraîneurs et les chercheurs pour essayer de gagner un peu plus de connaissance sur les facteurs associés à une bonne performance. L’intégration des technologies (vidéo et de la force) dans un emballage facile à utiliser, qui est à la disposition de l’entraîneur, pour l’évaluation sur site des performances est une prochaine étape dans la présentation d’outils pour la collecte d’informations sur la performance des athlètes. D’ailleurs, la compréhension des informations en provenance de ces technologies et comment elles peuvent être utilisée pour évaluer et améliorer les performances est importants. Cet article va examiner et décrire l’intégration des technologies utilisées avec les athlètes élite canadiens pour les évaluations de leur performance (compétences). Des exemples pratique seront fournis pour le sport olympique de la luge et le sport paralympique de natation, montrant comment l’intégration des technologies on été mises en œuvre dans des environnements de formation sur place pour fournir des informations en temps réel pour l’amélioration des performances.
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echnology in sport is evolving at a bewildering pace. In the overall goal to improve performance, it is vital for the coach to understand what technologies are available for analyzing athlete performances. Technologies in sport are readily available and can be used to measure motion (e.g., video cameras) or measure forces (e.g., force sensors). Both types of technologies are equally important in the assessments and ultimately the improvements of athlete performances. More important than the understanding of these technologies, their features and proper functionality, is the understanding of how to integrate these technologies within the dynamic sport environment. Also, it is very important to understand how information is extracted and interpreted from these technologies. www.sirc.ca
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In this article, we will explore the use of technologies, such as video and force sensors, in practical sport settings. A basic description will be provided about the technologies, the information that they can gather, the interpretation of data and the overall usability of these technologies in an applied sport setting. Additionally, we will see how these technologies can be integrated into easy to use tools that provide valuable information with immediate feedback to the athletes and coaches. Practical examples will be provided for the Olympic sport of Luge and the Paralympic sport of Swimming. First, we will provide a brief primer in biomechanics, describing the measurements of motion and forces.
SIRCuit Volume 1 (2) Fall / automne 2010
Measurement of Motion: Kinematics Kinematics is the study of geometry of motion. It is not concerned with the forces that cause the movement, but the details of the movement itself. When performing video analysis without any other measurement systems, coaches are only analyzing the kinematics. In other words, information extracted from video is singularly related to the analysis of kinematics unless the coach uses other measurement systems with the athlete (e.g., force transducers, muscle electrodes, etc.). The video camera is a tool that is being used on a regular basis to collect information with regards to athlete performances during training and at competitions. The video camera is also known as a “camcorder” and is defined as a portable device capable of recording video and audio. Video is collected on the camcorder and is stored either on digital tape or on the memory (hard disk) on the video camera. The storage format will depend on the type of camcorder that coach is using. Video footage can be downloaded to a computer for better viewing and analysis. Computer software that is specifically been designed for analysis of sports movements can be used to view and perform analyses of the video. One such software package for analysis of sports is called Dartfish. An image of the Player Module within Dartfish is shown in Figure 1.
Figure 1: Screenshot of Dartfish video analysis software showing image of sprinter performing start. Click image to enlarge
Software such as Dartfish can provide a coach with a tool to be able to capture, breakdown and analyze a movement of their athlete in order to make the necessary corrections in techniques. Information such as distance, speed, acceleration, and joint angles can be extracted from the video with the tools provided within the software. www.sirc.ca
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Figure 2: Force sensors implemented within the handles used in the start for the sport of Luge. Sensors measure both the vertical and horizontal forces applied for the left and the right hands independently. Click image to enlarge
However, measurement of just kinematics or motion does not provide insight into the forces that are responsible for causing the motion. Measurement of Forces: Kinetics Kinetics is the study of forces that lead to movement; furthermore, these forces can either be external or internal. External or reaction forces are produced by a body or an object making contact with another object thus producing an equal and opposite force to the direction that the original force was applied (reaction force). Internal forces are a function of the soft tissues within the body such as muscle, tendon, cartilage, and ligament. Internal forces dictate how athletes move and ultimately how they perform. Measurements of forces are typically not trivial and require customization of technologies in order to collect, analyze and summarize information. The measurement of external reaction force is more easily achieved and there are many commercially available force measurement devices that can be used. The principle is simple; measurements are made of forces exerted on the system that the athlete is pushing/pulling against. For example, in the case of the sport of Luge, the athletes are pulling on handles at the start to propel themselves forward. Therefore, implementation of force sensors within the handles provides information on the “pull forces” of the athletes. Figure 2 illustrates forces sensors that have been implemented into the luge pull handles. Performance Analysis of Luge Start: Using force and video measurements A strong start is vital in the overall performance of competing in luge. If the athlete does not pull fast to move the sled at a high velocity during the beginning of the SIRCuit Volume 1 (2) Fall / automne 2010
Figure 3:
Images of the pull start in the sport of Luge. Angles and distances are shown drawn on top of the athlete. Analysis is done of joint angles and distance that the sled is travelling.
run, his or her chance of a good performance is reduced. Along with looking at the forces, we can also break down A good start in luge is made up of a combination of an the movement to analyze the kinematics. Images above in athlete’s strength, flexibility, and proper technique. Figure 3 show the breakdown of the luge start. In order to make measurements of an athlete’s performance in the start of luge, both video and custom force sensors implemented into the pull handles were used. A real-time collection and feedback system was created to provide athletes and coaches information about the movement and forces of the pull start. Information such as forces that each hand was pulling with (vertical and horizontal direction) and position of the body throughout the movement could be analyzed. The video clip here shows slow motion videos of the pull start from two different athletes. Forces are overlayed on top of the video showing the forces exerted during different parts of the pull.
Analysis of the data is important to determine how to help improve the performances of the start. Table 1 below shows information on starts of 9 athletes. Performance times listed 2nd column from the left of the table. Force information gathered from each of the force sensors is located in all other columns.
Table 1:
Based on analysis of data, it was found that pulling with more force in the horizontal direction and pulling more symmetrically (right and left doing same thing) were important factors that maximized performance. This information is used to help developmental athletes improve and help high performance (Olympic) athletes fine tune their techniques to optimize performances.
The video clip here shows slow motion videos of the pull start from two different athletes. CLICK HERE
Horizontal forces (red and green lines) and vertical forces (blue and yellow lines) are shown on the graphs. The left video represents a more senior athlete and the right video a more junior athlete. Notice that the more senior athlete is pulling with much higher force, however, he has some asymmetry from right to left which may be detrimental to his start performance. The more junior athlete has more symmetrical pull, but much lower forces.
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Performance time and force data from 9 athlete pulls. Click image to enlarge
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Performance Analysis of the Swim Start (Paralympic): Using force and dual video systems A proper start off the blocks in swimming, using optimal technique and maximizing forward propulsion, is vital in the overall performance of a race. A good start is made up of the ability of the swimmer to maximize the forward forces off the blocks, propel forward into the water covering a large distance, and making sure that body position upon entry into the water is streamlined. In order to collect information to assess performances of the swim start it is not only important to capture video, but also information SIRCuit Volume 1 (2) Fall / automne 2010
about the forces between the feet and the blocks. An integrated video and force system was created to collect performance information of swim starts off the block for Paralympic swimmers. This system consisted of two video cameras (one over water and one under water) and two force platforms that could measure forces in the horizontal and vertical directions. The force platforms could be customized for position on the block for each athlete depending on their foot position (traditional two footed start vs. track start). Simultaneous video and force information were collected and integrated. The slow motion video presented here shows a start of a swimmer with horizontal forces overlayed on top of the video. Information can now be viewed of the technique of the start (motion) with forces of how the athlete is pushing off the blocks synchronized with the video.
best predictors of their performance was the capability of them to produce the largest combined (total right and left foot) horizontal force over time (referred to as impulse). The data for horizontal impulse is found in the last column of the table. We can now use this information to help the athlete optimize the performance of their start. The technique of the athlete’s start can be broken down by using the video. In the video presented here, we have taken the “Best” performance of an athlete (left video) and compared it to the “Worst” performance of an athlete (right video).
The “best” performance of an athlete (left video) compared to the “worst” performance (right video) Click to watch video Start of a swimmer with horizontal forces overlayed Click to watch video
Information gathered from the force platforms were summarized for each athlete. Data such as maximal forces in the horizontal and vertical directions were analyzed and summarized. Table 2 shows force summaries from one athlete for five repeated dives (trials) off the block.
The best and worst performances are defined by their performance times. You will see that the athlete swam 2.27 sec for his best and 2.85 sec for his worst performance. Breaking down the start we can see the technique of the athlete for his best and worst performances. Additionally, we can combine both the over water and under water videos together to show both to show the dive and subsequent entry into the water. The video seen here shows the videos combined into one.
The data from this particular athlete showed that one of the
Combining both the over water and under water videos. Click to watch video
Table 2: Performance and force data summarized for one athlete performing five repeated dives. Click image to enlarge
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Figure 4 (click here to see figure 4) shows the broken down movements for an athlete’s performances with both over water and under water views. Combining information about the movements and the forces, we can begin to understand the important factors that are leading to good performances and begin to make recommendations to individual swimmers as to how they should be changing their techniques to optimize their performance. Summary When planning and creating an integrated system to measure athlete performances, many important factors must be considered. First, there must be a clear understanding of what the final outcome will be and the information that will be required by the coach and athletes to improve performances. The next step would be to investigate and understand the venue in which the system will be used. There may be some adverse conditions that you will need to plan for, such as cold conditions for luge or wet conditions for swimming. Then, an investigation of the technologies that will best suit your needs will be initiated, followed by testing, customization and implementation. Throughout the process, one must realize that the system and method that you create to collect/process the performance data, must not be restrictive to the athlete. In other words, you must make sure that what you are using to collect the information is not changing the technique of the athlete.
The work performed with the Canadian Luge team was highlighted on Discovery Channel’s Daily Planet. To watch the video of this episode click below:
It was shown that the video combined with the measurement of forces was a valuable tool for collecting performance data for two completely different sports. The principles that are applied for the analysis of the video and the force data are similar for the two sports. The customization of the systems was different and was dependent on the needs of each sport. These types of integrated technologies can be applied to many other sports with proper planning and customization. ∆
Did you know... Dartfish users won 162 medals at the 2010 Vancouver Olympic Games in various events. It represents nearly 62% of the overall medal total. www.dartfish.com
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High performance at its peak
Visit our website to find out more about Canada’s efforts to own the podium
ownthepodium.org
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Performance Beat the Heat
Optimising performance in a less than optimal environment by Gordon Sleivert, PhD, VP Sport Performance, Canadian Sport Centre Pacific
For Gord Sleivert’s bio
CLICK HERE
Abstract
This article briefly summarises the key factors that limit performance in a hot environment and reviews practical strategies for coaches and athletes to optimize performance and training in hot weather. Primarily these strategies are focused upon minimizing the rise in deep body temperature and reducing the strain the body experiences as a result of exercising in the heat. Advanced preparation is critical and a primary strategy is to ensure athletes are aerobically fit, have adapted to exercising in hot conditions through regular and systematic exposure to the heat (heat adaptation), have appropriate clothing to maximize heat loss and protect against solar radiation and understand the venue hot-spots. Even with an aerobic base, individual responses to exercising in the heat vary widely and a key preparation strategy is to evaluate individual differences by simulating the environment during training or holding a hot-weather training camp. Key factors to monitor include; 1) rate of body heating 2) sweat rate and composition 3) thermal tolerance 4) perception of effort and thermal comfort. With these differences identified then countermeasures and strategies can be implemented to optimize an athlete’s training and performance. Modifying warm-up and using precooling to reduce heat storage prior to competition are key strategies for enhancing performance in the heat. Additionally, using the information gathered through monitoring it is important to work with athletes on hydration strategies to match sweat and salt losses as best they can and adjust tactics and pacing for the conditions. With sufficient advanced preparation and the adoption of some or all of the acute countermeasures presented in this papers those that struggle with the heat will likely improve both their training and performance. For those that are accustomed to hot weather training, these strategies may provide a small performance edge that makes the difference to getting on the podium.
Résumé La capacité qu’a l’athlète de haut niveau à répéter des efforts à une intensité élevée, qu’ils soient reproduits dans une même journée ou lors de plusieurs jours consécutifs, repose grandement sur sa capacité à récupérer. Cette récupération peut être optimisée en ayant recours à différentes méthodes, certaines n’étant pas encore éprouvées. La grande disponibilité des boissons énergétiques commerciales ou de conception artisanale, ainsi que leur efficacité potentielle pour optimiser la récupération leur confèrent un rôle d’importance dans le rituel d’entraînement de l’athlète. Leur consommation, de sorte à en tirer les bénéfices maximaux pour la récupération, doit toutefois respecter certains principes clés. Une boisson énergétique qui permettra à l’athlète d’optimiser sa récupération à court terme devra contenir, au moins, trois principaux ingrédients : un volume d’eau, une certaine quantité d’électrolytes et des glucides. La concentration de la boisson en électrolytes et en glucides, ainsi que le type de glucides, pourront affecter l’absorption de la boisson par le tube digestif, sa capacité à réhydrater et à restaurer les réserves de glycogène musculaire. Il est bien établi que la présence d’une légère déshydratation et/ou de faibles réserves en glycogène musculaire, dans plusieurs sports, peuvent entraîner des réductions significatives de performance. Pour cette raison, une connaissance accrue des mécanismes pouvant influencer la récupération à court terme des athlètes pourra aider l’entraîneur (et l’athlète) à choisir une boisson énergétique qui lui conviendra et lui permettra d’améliorer sa performance à moyen et long terme.
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anadian athletes are often faced with the challenge of leaving a cool or even cold environment in Canada to compete in unaccustomed hot environments. The sheer size and regional diversity of Canada also ensures that coaches and athletes frequently face hot weather challenges. This article briefly summarises the key factors that limit performance in a hot environment and reviews practical strategies for coaches and athletes to optimize performance and training in hot weather. PHYSIOLOGICAL STRAIN Training and performing in a hot environment, especially when unaccustomed to such weather, introduces many additional challenges for the athlete. The primary physiological change when exercising in a hot environment www.sirc.ca
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is a rise in deep body temperature, also known as core temperature. High air temperatures limit the body’s ability to dissipate heat because the temperature gradient between the skin and the surrounding environment approaches zero. High ambient temperatures in combination with heat produced by working muscle during exercise can increase core temperature dangerously above the resting level of 37ºC. If the weather is humid then the bodies major mechanism of cooling – the evaporation of sweat – is also impaired because the water vapour pressure gradient is reduced, i.e. sweat cannot evaporate into air that is already mostly saturated with water. In addition to a rise in core temperature these conditions result in increased skin temperature which has a profound effect on thermal perception. When the skin is hot the athlete feels SIRCuit Volume 1 (2) Fall / automne 2010
regularly train aerobically may be considered to be between 50 and 75% heat acclimated. This is due to the fact that aerobic exercise regularly increases body core temperature – the key stimulus for heat adaptation, and enhances cardiovascular fitness so the body is better able to handle the increased cardiovascular strain required when blood must be shared between working muscle and skin.
Figure 1: Mechanisms of heat gain or loss when exercising in a hot environment.
uncomfortable and this has been demonstrated to influence pace selection and exercise intensity.
ADVANCED PREPARATION When coaches and athletes know they will be training and or competing in a hot environment there are a number of things they can do to prepare in advance and these are briefly outlined below: 1. Build Aerobic Fitness. It has been well demonstrated in the scientific literature that more aerobically fit athletes better tolerate training in the heat and indeed may have an enhanced tolerance to higher core temperature1. Indeed, athletes that www.sirc.ca
Tcore (deg C)
In an attempt to maintain body temperature near normal, the bodies controller - the brain - responds to the rise in both core and skin temperature by distributing more blood to the skin and activating the sweat response for evaporative cooling. In doing so blood must now be shared between the active muscle and the skin, so heart rate goes up, and with the increased sweating, fluid is lost. When these additional strains are combined it has been repeatedly demonstrated that both the intensity and duration of exercise can be compromised which of course can impair both training and competitive performance. Other negative effects of heat on the physiology of performance include an increased contribution of anaerobic metabolism and blood lactate accumulation at a fixed work rate and an increased rate of carbohydrate use by working muscle. Thankfully there are proven strategies to minimize the deleterious effects of the heat on the athlete and when properly utilized these strategies can provide athletes with distinct advantages over lesser prepared competition. These strategies can be separated into two categories; 1) Advanced Preparation and 2) Acute Countermeasures.
2. Identify Individual Responses. A strategy I have used for over 15 years with individuals and teams heading for the heat is to exercise individuals in simulated hot environments and or hot training camp environments and monitor factors such as the rise in their body temperature with exercise, the loss of fluid through sweating, the sodium content of sweat and the psychophysical response of these athletes to the conditions, i.e. How hot do they feel? How uncomfortable are they with being hot? The Sport Scientists today has many tools that allow them to monitor these factors in the field. Our laboratory has used ingestible temperature sensors since 2003 in sports as diverse as Triathlon and Wheelchair Rugby to monitor how core temperature changes with exercise in the heat and we have been able to identify athletes that particularly overheat and have challenges coping with the conditions2. From this we can work with the coach on pacing and substitution strategies, the implementation of countermeasures such as pre-cooling, or the 40 39.5 39 38.5 38 37.5 37 36.5 36
Mean increase 1.4 deg C Rest
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Figure 2: The body temperature response of triathletes performing a group 8k interval workout in the heat. Note the triathlete represented by the pink line heated up to a far greater extent than others doing the equivalent work-out.
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improvement of other factors that influence their response to the conditions such as warm-up, clothing etc. Additionally by monitoring sweat rate, fluid consumption and supplement strategies in individuals, and also in some cases looking at sodium loss we can individualize hydration and nutrition plans for each athlete we are working with. 3. Heat Adaptation. Repeated exercise sessions in the heat over four to 10 days can improve performance in hot conditions through a number of physiological adaptations3. Sweat rate increases, while salt concentration of the sweat is reduced. The nervous system eventually adapts and sweating begins at a lower core temperature. Indeed resting core temperature is often lowered by up to 0.3 deg C which allows athletes more room before they overheat. Blood volume also increases. Ultimately this leads to a lower rate of rise in core temperature and heart rate. The body relies more on carbohydrates as a fuel when it is first exposed to a hot environment, thus more lactate is produced. After repeated exercise in the heat, fuel selection is similar to that in a cooler environment and carbohydrate is spared4. Taken together, these benefits improve heat tolerance, increase work output and improve performance in the heat. Guidelines for heat adaptation: Heat adaptation strategies typically involve up to 10 days of exercising in the heat (>30ºC), but changes can occur in as few as four days, and for many athletes approximately 5 days of consecutive exposure to the heat is sufficient5. This can be achieved naturally in a warm climate (heat acclimatization) or it can
Figure 3: A)The deep body temperature of two triathletes riding in hot conditions near Penticton. Because of the convective cooling during riding, core temperature did not increase high enough for long enough to elicit the appropriate stress for optimal heat adaptation
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be simulated artificially using sweat clothing or artificially hot environments (heat acclimation), an environmental chamber is optimal but a small room with heaters can also be very effective. Sweat clothing is less effective. The goal of heat training is to significantly elevate core temperature (38.5ºC for approximately an hour) and drive physiological adaptations to this state so that athletes can better tolerate hot conditions. This approach to heat adaptation is termed Controlled Hyperthermic Exposure and has been demonstrated in the literature to be very effective6. Below is an example of how a session could be constructed. •
•
• •
Start the training session at moderate to high intensity for the first 20-30 minutes (or use hard intervals) to elevate core temperature (target 38.5ºC) and then decrease the intensity to maintain core temperature at 38.5ºC for the remainder of the workout. If core temperature cannot be measured (you need to work with a physiologist), then measure heart rate (7580% of heart rate maximum) for the first 20-30 minutes and then reduce the intensity (40-50% of heart rate maximum) for the next 40-60 minutes. Don’t assume that just because it is hot out that athletes increase core temperature enough to stimulate acclimatization (consider effects of convective cooling through wind, shade and the intensity of the workout). Optimally measure core temperature to confirm the state of hyperthermia The ideal environment for heat adaptation
Figure 3: B) The same triathletes performing a roller session with convective cooling. This controlled hyperthermic exposure provided the optimal thermal stress for heat adaptation, ie. they were hot enough for long enough.
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0.035
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100% Cotton
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Evaporative Resistance (m2·kPa·W-1)
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Fabric Properties. Our lab at the Canadian Sport Centre partners with the Sport Innovation Centre (SPIN) at Camosun College to quantify thermal and moisture management properties of fabrics using a technical piece of equipment called a sweating hotplate. The key characteristics we look for when examining fabrics to be used in garments for hot weather work are 1) low thermal resistance - heat transfers through the fabric well and 2) Low evaporative resistance - water and water vapour transfer through the fabric and the boundary air layer under the material well. Evaporative heat transfer is the most important means for dissipating heat during physical activity. If evaporation is prevented then sweat begins to pool on the body surface and eventually drips off the body. This pooling does not contribute to heat dissipation. Consequently evaporative resistance is a crucial component of performance apparel fabrics. The evaporative resistance is a measure of what is more often termed the ‘breathability’ of a fabric. A higher evaporative
are optimal for hot weather.
Hot Weather
4. Clothing. What an athlete wears influences their body temperature and exercise performance in the heat and this has been known for years. Indeed, the development and marketing of technical clothing that assists with heat management is front and centre in the sports world. The utility of technical clothing for the heat is dependent upon two factors: 1) the physical properties of the fabrics used to construct the garment and 2) the fit and structure of the garment 8.
resistance score would indicate a greater barrier to the movement of water vapour away from the body surface than a fabric with a lower resistance. Therefore the lower the evaporative resistance, the more ‘breathable’ a fabric is, thus the more effective at keeping the individual cool and dry. As a result sports apparel fabrics should have as low an evaporative resistance as possible for all climatic Figure 4: The thermal and evaporative resistance values as measured using a sweating hot plate in our laboratory on conditions. fabrics used in brandname hot and cold weather technical garments and a 100% Cotton shirt. Low resistance values
Thermal Resistance (m2·°C·W-1)
is one that is hot and dry because this drives sweating. In hot and wet environments the sweating can be attenuated though prolonged skin wetness and swelling of the epidermis (hydro meiosis) 7.
Fabric
Figure 4: The thermal and evaporative resistance values as measured using a sweating hot plate in our laboratory on fabrics used in brand name hot and cold weather technical garments and a 100% Cotton shirt. Low resistance values are optimal for hot weather.
These are pre-requisites in choosing whether a garment will perform well in the heat. The fabric properties are influenced by the fibres used to make the threads and yarns, the knit structure and porosity of the weave and the finishes used on the fabric8. Microscopy can be used to examine these factors and judge their influence on the physical properties discussed above, additionally, colours that reflect solar radiation (usually light) are better than those that absorb radiation. Sports interested in comparing these properties between two different fabrics or
Figure 5: A micrograph showing the three different fabrics reported in figure 4. Based upon the weave and porosity of these fabrics it is not surprising that their physical properties are quite different.
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SIRCuit Volume 1 (2) Fall / automne 2010
Rectal Temperature
Body Temperature
Heart Rate
Physiological Strain Index
mean
final
change
mean
final
mean
final
(oC)
(oC)
(oC)
(oC)
(oC)
(bpm)
(bpm)
Summer Tech
37.8
37.9
0.8
36.7
36.7
126
Winter Tech
37.8
38.2
1.2
37.3
37.7
100% cotton
37.7
38.2
1.7
36.8
37.3
Sweat Rate
mean
final
(L/hr)
145
3.9
5.1
0.80
136
154
4.8
6.3
0.96
136
153
5.0
6.7
0.89
Table 1. The physiological response of a female subject during 1 hour of cycling while wearing different performance shirts in a moderately warm environment.
uniforms to be worn in the competitive arena can work with SPIN to quantify such properties allowing objective decisions to be made when choosing a garment for hot conditions. (See Figure 5). Fit and Structure. Although technical sport clothing is often marketed based upon factors discussed above such as “breathability”, the reality is that other more pragmatic issues contribute equally to how a garment or garment assembly performs for the athlete in extremes. For example, a loose fitting garment is often better in the heat because it allows air flow to the skin and provides a bellows effect, which enhances convective and evaporative cooling of the skin. This of course needs to be balanced with aerodynamic requirements in some sports. The total surface area that a garment covers is another factor, and in the heat less coverage is usually better because evaporation of sweat is enhanced with uncovered skin. Not since Ancient Olympia have athletes competed naked so this needs to be balanced with protection from solar radiation and a hat and other clothing is often necessary to protect from the sun. Finally the strategic use of vents, combinations of fabrics constructed into a garment to optimise cooling but also provide protection, and the advent of smart clothing, which changes depending upon the stressors detected from both the environment and athlete, are all important considerations in choosing the right clothing for the situation. We test the physiological response of athletes to a standard exercise dose in controlled environmental conditions to compare how different garment assemblies work in the heat. By monitoring body temperature changes, heart rate and sweat rate along with the athletes perceptual responses we are able to most effectively make objective decisions about which clothing set-up is likely to perform the best. (See Table 1) 5. Thermal Mapping. It is often useful for the www.sirc.ca
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Spin Textile Testing Introduction
Click to watch video
coach or support staff to tour the competition or training venue in advance of the athletes arriving and gauge those areas that are hottest and those that may be the coolest. This thermal mapping of the venue can be done systematically with a portable weather station but usually can be accomplished quite adequately with a keen eye and careful observations. Note the direction of the sun, where shade exists, the prevailing wind, areas where solar radiation is stored and emitted (i.e. Asphalt) and stake out your staging territory in those areas that will be the coolest. If racing over a longer distance there may be strategic decisions required to reduce exposure to the sun or take advantage of particular conditions. Bringing umbrellas, tents or awnings and even portable fans can make the venue just that much more tolerable. (See Figure 6) Performance Strategies 1. Take the “warm” out of warm-up! In general when competing in the heat, especially for endurance events or longer games, warm-ups should be reduced in either length or intensity to ensure that athletes do not start their competitions too hot thereby compromising the intensity they will be able to work at in the later stages of competition. It has been demonstrated that once the core temperature gets too high (>39,5 deg C) the brains ability to activate working muscle is impaired so avoiding overly high core temperatures is critical SIRCuit Volume 1 (2) Fall / automne 2010
the event and practical considerations. It is important to note that when using ice-vests to pre-cool usually core temperature is not reduced. Rather, the rise in body temperature during a warm-up is attenuated so the athlete starts their performance at a cooler than normal body temperature. (See Figure 7) Post-cooling may be defined as active cooling to reduce skin and/or deep body temperature postexercise and/or between events or training sessions. Between events it may help return body temperature to normal rapidly and delay the attainment of a critical body temperature in subsequent events. It may also be a necessary treatment for exertional heat illness or heat stroke. Post-cooling of previously active muscle may also reduce immunologic and metabolic tissue stress and facilitate recovery between training sessions. The hands and feet are especially good heat exchangers because they have many arteriovenous-anastomoses (AVA’s) that open with hyperthermia11. The fastest method of postcooling is full-body head out immersion in 2°C water (reduce body temperature on average from 39.5°C to 37.5°C in 8 minutes) 12. Cooling vests may provide benefits. The maintenance of adequate mean arterial pressure is also a key to rapid cooling, so moving slowly or lying down with the feet-up can be useful to help with cooling down after exercise. (See Figure 8)
Figure 6: The 2004 Athens Olympic Competition Pool: Thermal mapping indicated the best places for athletes to locate themselves while watching the competition.
to performance9. For sprint and power events however, as long as the body temperature is not too high, muscles will function better when heated and performance is often enhanced in the heat, so the strategy to be used is event/sport dependent. 2. Cooling. Pre-cooling can be defined as active cooling to reduce skin and/or deep body temperature prior to exercise. There is good evidence that precooling can enhance performance in events taking between several minutes to a hour10. It may delay the attainment of a critical body temperature associated with fatigue, enhance psychophysical response to heat, positively influence pacing and reduce cardiovascular and thermal strain. Cold water immersion (for 15 minutes), or ice vests such as the Thermoblazer (for 60 minutes during warmup) are all effective modalities for pre-cooling and come with both advantages and disadvantages. The selection of a pre-cooling method is dependent upon
A
Control
39.0
Work Done (kJ)
Temperature (°C)
39.5
Suggested Protocols. Pre-Cooling: • Choose a modality or modalities that suits sport and venue • Order cooling system early and
Torso Whole
38.5 38.0 37.5 37.0
Steady state (N=9)
36.5 Base 0
5
10
15
20
Self-paced (N=8)
25
30
B
35
Time (min)
250
Control (C)
200
Torso (T) Whole body (W)
150 100 50 0
20
25 30 Time (min)
35
Figure 7: Cyclists riding in the heat started at a lower body temperature when either the torso or whole body were pre-cooled versus no pre-cooling (control) and maintained a lower temperature over the course of A) 35 minutes of exercise. B) During Self-paced exercise cyclists were able to work harder after pre-cooling.
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SIRCuit Volume 1 (2) Fall / automne 2010
it is just as important to drink adequate fluids in maintaining coordination, concentration and ensuring that recovery is optimized. Although most athletes and coaches are aware of the importance of hydration, recent data collected from our performance services team indicate that greater than 50% of high performance athletes are not adequately hydrating during training and or competition. [Click here to see Figure 10] Figure 8: The Thermoblazer Ice Vest being used by Olympic Triathlete Brent McMahan
•
Figure 9: Beijing Olympic Medallist Ryan Cochrane cools down after a hard training session to enhance recovery
practise method before implementation Apply cooling before and during active warm-up for up to 1 hour
The saltiness of sweat varies immensely between individuals and we routinely utilize sweat testing and sweat sodium measurement to identify is an athlete is a salty sweater or not. For those athletes that lose a lot of sodium in their sweat we work with a dietician to ensure they get more sodium in their diet and in some cases we increase the sodium content of their sport drinks. (See Figure 11)
Post-Exercise Cooling: • Whole body immersion in 20°C water is optimal • Target hands, feet upper-chest and neck if you cannot use whole-body immersion. Cooling-vests may help and should be worn during active cool-down for up to an hour • Maintain blood pressure by slowly moving (muscle pump) and adjust posture for headdown feet-up. (See Figure 9)
Calculating Sweat Rate The calculation of sweat rate quantifies the amount of fluids lost, providing more tangible guidelines for fluid replacement. The following is a simple step by step breakdown of sweat rate calculation. Since it takes 30-40 minutes to fully “turn on” sweating, this calculation can underestimate sweat rates when used for exercise periods of short duration. [Click here for “Calculating Sweat Rate” table]
3. Hydration. Since sweat rate is so high during exercise in the heat, fluid replacement is essential. It is known that dehydration can impair performance and that being dehydrated by as little as 2% of body mass can slow an endurance athlete down and impair their ability to regulate body temperature13. For athletes in team sports or speed/power events
Sweat Loss and Sweat Rate 1. Equipment required: weigh scale (accurate to 0.1kg), stopwatch, and a premeasured waterbottle in milliliters (ml) 2. Measure body weight to the nearest 0.1kg prior to exercise 3. Measure volume of fluids to be ingested
Figure 11: Sweat testing data from two sisters who are marathoners. They visited the lab on two occasions. One Sister (SP) has very dilute sweat while the other (WP) is a salty sweater, whom must consume more sodium in her diet when in intensive and high volume training phases.
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SIRCuit Volume 1 (2) Fall / automne 2010
during exercise (in ml) and place in water bottle start stopwatch when exercise begins; drink fluid as normal; record volume of fluid left at end of session 4. Stop stopwatch when exercise ends; record time 5. Take post exercise body weight (make sure you are dry and that all wet clothing has been removed) 6. Measure out any remaining fluids from water bottle; record leftover measurement (in ml) 4. Tactics and Pacing. As previously mentioned the ability to exercise in the heat is usually compromised and it has been well demonstrated that pace in events over approximately 15 minutes in duration is usually compromised in hot conditions14. Nevertheless, one of the most common mistakes athletes make in the heat is to select too aggressive a pace that cannot be sustained. Coaches should be cognizant of this and race plans and substitution strategies for team sports should be tested and implemented that recognize this. The figure below illustrates the deep body temperature of a race walker testing a pace that he felt was appropriate for the conditions at the Athens Olympics in 2004. As can be seen with the model the pace was too aggressive and the walker would overheat in less than 20km. This information was utilized to assist in developing a more conservative race plan. [Click here to see Figure 13] Many athletes train and compete safely in hot environments around the world. With sufficient advanced preparation and the adoption of some or all of the acute countermeasures presented in this papers those that struggle with the heat will likely improve both their training and performance. For those that are accustomed to hot weather training, these strategies may provide a small performance edge that makes the difference to getting on the podium. ∆ For References, click here
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Simple Performance Points That May Help Athletes To Stay Hydrated And Train And Perform Optimally
Hydration before Exercise
• Most individuals dehydrate overnight by at least 1 L. Keep a water bottle at bedside for easy access to fluid during the night. Upon waking consume several glasses of water. • Be organized. Always carry a drink bottle and sip water regularly during the day. Don’t wait until you are thirsty to drink. • Drink 250-500 mL of water 30-60 minutes before exercise.
Hydration during Exercise
• Practice drinking during training and aim to keep dehydration about 1% of body weight, or replace about 80% of sweat loss. For example, if you lose 1 kg during training that equates to approximately 1 L of fluid and you should be aiming to drink at least 800 ml. • For endurance exercise or long training sessions a carbohydrateelectrolyte drink will provide both fluid and energy. As a general guide, ingest 200-250 mL of 6-8% carbohydrate drink every 15-20 minutes (up to ~60g carbohydrate/hour). • In very hot conditions, diluting a sports drink by 15-20% may enhance fluid absorption. • Drink cold fluids that you like. Fluids that taste good at rest may not taste so good while exercising, therefore it is recommended that you try different flavours and concentrations.
Hydration after Exercise
• Replace fluids, carbohydrate and sodium lost during exercise to minimize dehydration, to stabilize blood volume, and to avoid muscle cramps. Carbohydrate and sodium is best replaced through food intake! • Fluid loss continues after exercise stops so you need to consume more fluid than your existing fluid deficit. For example, consume 3 L in 4 hours to achieve replacement of 2 L. • Athletes should all drink a minimum of 2L of water/day plus extra to replace losses from training/competition.
Monitoring Hydration State
• A simple way of checking hydration status is to monitor urine output. It should be clear or pale yellow and produced in sufficient volume. As urine gets darker, athletes are more dehydrated (however do note that some vitamin supplements and medications can also make urine darker). • We have used a digital refractometer in our laboratory with great success to track hydration state of athletes. This allows us to inform the athlete if they need to hydrate better and removes the judgement factor.
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SIRCuit Volume 1 (2) Fall / automne 2010
Sport Innovation Combining Hypoxic Methods for Peak Performance Millet et al. Sports Medicine (2010) 40(1): 1-25. Commentary by / Commentary par Dr. David J. Smith; Director of Sport Science - CSCC and Professor, Human Performance Laboratory - University of Calgary
P
L
erformance enhancement can be achieved by many different methods. One such method is the use of some form of hypoxic training and/or altitude exposure to induce an improvement in athletic performance at sea-level. The purpose of this review by Millet et al. is to propose a combination of hypoxic methods including the techniques of living high-training high combined with living high-training low/high intensity and intermittent hypoxic exposure/ training. The evolution of altitude training which began in the 1960’s, and has become part of the endurance training culture over the last two decades and current thinking is that through combining different hypoxic methods into a periodized training plan, creates a greater performance enhancement than each hypoxic method in isolation. The traditional altitude camp consists of living and training at a moderate altitude for several weeks, usually between 2 and 4 weeks. This methodology has evolved into live high-train low/high intensity in order to obtain the beneficial effects of altitude whilst avoiding the decrease in training intensity which can occur when training at higher elevations. The last evolution involves intermittent hypoxic exposure or training which is defined as exposure to hypoxia lasting from seconds to hours that is repeated over several days or weeks where the hypoxic exposure is as high as 4,000 - 5,000 m. This review examines all of the above methods and places particular emphasis on potential or demonstrable effects on performance not only in endurance athletes but also in “glycolytic” sports and intermittent sports. The authors have proposed a combination of these hypoxic methods in the yearly training plan. However, sport scientists could debate at length the merits and concerns of the different models proposed but it is important for coaches to recognize that there are many different ways to use hypoxic environments to enhance performance. This paper offers a challenge to coaches to examine how they may use these techniques in the development of long-term training plans. ∆
’amélioration de la performance s’effectue grâce à différentes méthodes. L’une d’elles est une méthode d’entraînement à l’hypoxie et/ou d’exposition à l’altitude pour susciter des gains de performance physique au niveau de la mer. L’objectif dans cet article documentaire de Millet et coll. est de présenter une combinaison des méthodes d’entraînement à l’hypoxie intégrant des approches de séjour et d’entraînement en altitude, de séjour en altitude combiné à un entraînement de forte et de faible intensité et de séances intermittentes d’exposition et d’entraînement à l’hypoxie. L’entraînement en altitude qui se pratique depuis les années 60 a intégré la culture de l’entraînement en endurance au cours des deux dernières décennies. Actuellement, il semble acquis que la combinaison de diverses méthodes d’utilisation de l’hypoxie dans un programme d’entraînement périodisé suscite de meilleurs gains de performance que chacune des méthodes hypoxiques utilisées séparément. Le camp d’entraînement en altitude habituel est constitué d’un séjour à une altitude modérée combiné à des séances d’entraînement sur une période de 2 à 4 semaines. Cette façon de faire a évolué; on suggère maintenant un séjour à haute altitude combiné à des séances d’entraînement de faible et de forte intensité pour ainsi tirer profit des effets de l’altitude et éviter la diminution de l’intensité de l’entraînement observée en altitude. Cette nouvelle façon de procéder est constituée de séances intermittentes d’exposition à l’altitude et d’entraînement; les séances d’exposition à l’hypoxie, correspondant à une altitude de 4000 à 5000 m, durent de quelques secondes à quelques heures et sont reprises sur une période de quelques jours à quelques semaines. Cet article documentaire analyse les approches mentionnées plus haut et s’attarde particulièrement aux effets potentiels et démontrables en matière de performance non seulement chez les athlètes d’endurance, mais aussi chez les athlètes pratiquant des sports à dominante anaérobie et des sports composés d’activités intermittentes. Les auteurs proposent un amalgame de ces approches par hypoxie dans un programme d’entraînement sur une base annuelle. Néanmoins, les scientifiques du sport peuvent débattre sans fin des tenants et des aboutissants des diverses approches suggérées, mais les entraîneurs doivent savoir qu’il y a plusieurs façons de profiter des environnements hypoxiques afin d’améliorer la performance. Cet article invite les entraîneurs à examiner les diverses approches et à les utiliser dans l’élaboration de programmes d’entraînement à long terme. ∆
To order original article CLICK HERE
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SIRCuit Volume 1 (2) Fall / automne 2010
New Horizons for the Methodology and Physiology of Training Periodization Vladimir B. Issurin. Sports Medicine (2010) 40(3): 189-206. Commentary by Dr. Jon Kolb, Director Sport Science, Medicine, and Technology for OTP.
“N
Click here to listen to podcast
ew Horizons for the Methodology and Physiology of Training Periodization” is a well-referenced article by Vladimir B. Issurin, which was recently published in the journal Sports Medicine. This excellent review article is a great addition to this second edition of the High Performance SIRCuit because it reflects the direction that many of our High Performance Coaches are taking with periodization, and perhaps more importantly stimulates ideas and concepts that we should be sharing with all of our Junior and Development Coaches.
should ask themselves as they assess, monitor, and modify their annual training plans. The first question that came to mind was, have you the Coach developed the YTP based on sound periodization models specific to the dynamics of the sport? Secondly, has the coach included key IST members for input with regards to the design, organization of the ‘block phases’, and identification of dates for medical monitoring and performance profiling? The final question HP Coaches may consider in conjunction with their sport science, sport medicine team is, has the plan been challenged rigorously to be not only creative, but also innovative in scope to drive performance enhancement?
The article is organized into three major segments: The first being a review of traditional models that formed the foundation of our understanding of training principles. The second looks at alternative models of periodization and the development of linear and non-linear periodization. The final segment, which many High Performance Coaches utilize, describes the organization of athlete preparation into ‘block periodization’: focused periods of training with specific identified physiological parameters that are expected to evolve over time and then moving on to other parts and frame works of the training. The general idea proposes the sequencing of specialized training cycles, i.e. the reference to “blocks”, which contain highly concentrated workloads directed to a minimal number of targeted abilities. Unlike the traditional model, which attempts to develop simultaneous physiological functions, the block periodization training presupposes the consecutive development of reasonably selected target abilities.
In conclusion, Issurin’s take on periodization, is a great opportunity for NSOs to review their current methodology for athlete preparation, and generate a healthy debate on new directions that may result in more trips to the podium. ∆ To view original article CLICK HERE
Throughout the manuscript Issurin includes examples of periodization models for both team and individual sports. As well, another attribute of this article is that the keen scientist and coach will enjoy perusing a very lengthy and welldeveloped bibliography for further readings in this important area training design and planning.
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After reviewing the article, my general feeling was that there was not a lot of new information gained, rather the author brought clarity into highlighting the evolution of training periodization. Personally, the article generated a few questions that I think each of our NSO’s and HP Coaches www.sirc.ca
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SIRCuit Volume 1 (2) Fall / automne 2010
The International Olympic Committee (IOC) Consensus Statement on Periodical Health Evaluation of Elite Athletes, March 2009 Arne Ljungqvist, MD, PhD et al International Olympic Committee Medical Commission Clinical Journal of Sport Medicine (2009); 19:347-365. Commentary by Dr. Victor Lun Sports Medicine Physican - University of Calgary Sports Medicine Centre
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he International Olympic Committee (IOC) Consensus Statement on Periodic Health Evaluation of Elite Athletes further reinforces the importance for elite athletes to have a regular medical assessment. As much as a medical assessment is important for detecting potentially life threatening medical problems (such as cardiac arrythmias or structural abnormalities) and prevention of musculoskeletal injury, it can also be viewed as potentially performance enhancing. For example, appropriate management of exercise-induced bronchospasm can potentially prevent respiratory dysfunction that could affect athletic performance and recovery. Other important reasons for a regular medical assessment that are not discussed in the consensus statement include: review of medications and supplements that athletes are taking to avoid any anti-doping infractions and review of immunizations that may be needed for health maintenance and up-coming international travel. While there is probably no disagreement that athletes should have a regular medical assessment, implementing them can be difficult. Elite athletes are generally younger and usually free of chronic illness and may not see the importance of having a medical assessment performed. It may be difficult to find a physician to perform the assessments and for some sport organizations, it may be difficult to afford the cost of the medical assessments. From a more practical perspective, the implementation of medical assessments should be done in multi-disciplinary
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manner as the management of many musculoskeletal injuries and some medical illnesses often require the involvement of team therapists (physiotherapists, massage therapists, chiropractors), dietitians, strength/conditioning coaches and sport physiologists. Ideally, the medical assessments should be performed by a physician with sport medicine training as they will be more aware of conditions that affect athletes, be more familiar with sport activity and its physical demands, and finally, be up-to-date with anti-doping regulations. Although a medical assessment can be done at any time, doing the assessment at the beginning of the rest phase/off-season of an athlete’s training cycle may be more ideal in order to identify and treat all injuries and medical conditions prior to the beginning of the next competitive season/phase. A supplemental pre-competitive season assessment could also be added in order to ensure that any injury or medical concerns are appropriately managed during the competitive season. For decentralized sports, it may be easier to do the medical assessments during a training camp when athletes are gathered together in one location. Finally, in addition to a medical assessment, a functional assessment by a therapist should also be considered to help identify potential areas of sport-specific musculoskeletal dysfunction that require rehabilitation. ∆ To view original article CLICK HERE
SIRCuit Volume 1 (2) Fall / automne 2010
Upcoming Events For more events, check out the SIRC Conference Calendar. Click on the “month” below to see all events for that month.
Pour d’autres événements, veuillez consulter le calendrier SIRC des congrès. Ci-dessous, choisissez le mois pour voir tous les événements de ce mois
November ◊ novembre
February ◊ fevrier
CSEP (Canadian Society for Exercise Physiology) 2010 3-5 November 2010, Hyatt Regency Toronto on King, Toronto, Ontario, Canada
2011 International Hypoxia Symposia 15-20 February, 2011 Chateau Lake Louise, Alberta
2010 Petro-Canada Sport Leadership Conference - Ottawa 18-21 November 2010, Ottawa, Ontario, Canada
Family Medicine: Sports Medicine and Orthopaedics with hands on splinting/casting and joint injection models 26 February, 2011-5 March, 2011 Honolulu Hawaii, United States
ASICS uksem International Conference 2010 24-26 November, 2010, Docklands, London, UK
March ◊ mars
December ◊ decembre 5th International Congress on Science and Skiing 12-19 December 2010, St. Christoph am Arlberg, Austria
4th AFC Conference on Science & Football Medicine 18-20 March, 2011, Kuala Lumpur, Malaysia
6th ICCE Continental Coach Conference 2-4 December, 2010, Arnhem Country, The Netherlands
The 2nd International Conference on Sport Sciences and Sport Medicine 8-10 March, 2011, Cairo, Egypt 2011 AAHPERD National Convention & Exposition 29 March-2 April, 2011, San Diego, California
April ◊ avril
January ◊ janvier FIVB Volleyball Medicine Congress 13-15 January 2011, Bled, Slovenia
ACSM’s (American College of Sports Medicine) 15th Health & Fitness Summit & Exposition 11-13 April 2011, Anaheim, California
2011 Grand Slam Coaches Conference 13-15 January, 2011, Melbourne, Victoria, Australia
V International Congress “People, Sport and Health” 21-23 April 2011, St. Petersburg, Russia 2011 AMSSM (American Medical Society for Sports Medicine) 20th Annual Meeting 30 April – 4 May, 2011, Salt Lake City, Utah
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SIRCuit Volume 1 (2) Fall / automne 2010
Competitive Intelligence
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nowledge can give an athlete the competitive edge. Competitive intelligence equips coaches, sport scientists and practitioners with the latest information that may assist in the quest to put an athlete on the podium. SIRC receives thousands of publications from around the world each year ranging from peer reviewed journals to practical guides and our information specialists are constantly reviewing and indexing the various articles.
Coaching Stress: Causes, Costs and Coping
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A Commentary on the Literature by Nancy Rebel, Director of Library Services, SIRC and Michele Walker, Regional Manager, Ontario, SIRC
reat moments in sport are often remembered by the pressures affecting the outcome of the competition. Whether the pressure is applied by media, sponsors, parents or the fans, it comes from a variety of internal and external forces. But it’s not just the athlete who experiences these pressure situations. Often forgotten is the coach. Who can forget the powerful, dramatic and emotional images of Canadian figure skater Joannie Rochette mourning the death of her mother at the 2010 Olympic Winter Games, and imagining what pressures coach Manon Perron was under to continue and guide her Olympic medalist hopeful on the biggest stage in sport, while she also grieved the loss of her friend. And how can we understand the myriad of pressures facing Commonwealth Games coaches as they uncovered the unexpected challenges of conditions in the Athletes’ Village and venues in Delhi this fall. It is through examples such as these that we can truly see how coaches play a vital role in the achievements of highperformance athletes.
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Causes/Stressors: The one thing that all can agree on is that each individual is unique and therefore experiences stress within the context of their own personal environment. Each coach faces pressure in the adoption of multiple roles within their coaching context: instructor, mentor, friend, organizer, educator, counselor, motivator, strategist, and more. And the pressure of these roles is intensified in direct correlation to the degree of outcome-orientation of their position. While research has identified a number of causes of stress specific to coaches, several themes have been identified in the high-performance context including the following (Olusoga et al, 2009; Fletcher & Scott, 2010; Humphrey et al. 2000)): 1) Conflict with Sport Organizations Administration based issues such as conflicting coaching/organizational philosophies; tensions between staff; outside influences infringing on coaching roles and responsibilities; begin mindful of legal issues. 2) Pressure and Expectation Internal and external pressures placed 22
This article is also available as a podcast, click here to listen
upon coaches in terms of performance outcome; feelings of being under the microscope; not have ultimate control over the outcome of a sporting event as they are not the ones on the field of play; not wanting to let their athlete down. 3) Managing the Competitive Environment Managing coach time and athlete time during competitions; officials; opponents; unexpected events. 4) Athlete Concerns Behaviours and attitudes of athletes; team atmosphere; commitment; making sure athletes perform to their potential; motivating athletes; injuries and injury prevention. 5) Coaching Responsibilities to Athletes Meeting athletes’ training needs; managing large groups of athletes; managing athletes who themselves are dealing with stress, dealing with outside influences on athletes (social, drugs, etc.)
SIRCuit Volume 1 (2) Fall / automne 2010
6) Sport Status Lack of recognition for the sport; finances and budgets; adequate facilities; comparison with other countries; lack of personal recognition 7) Competition Preparation Maintaining elite status and high standards of training and performance; team selection; proper taper for athletes; adequate training time; scheduling; travel; safety. 8) Organizational Management Management of other people and organizations; prioritizing administrational duties; managing multiple roles. 9) Sacrifice of Personal Time Time demands affecting family and personal life; not enough time to get everything done; time demands of athletes. 10) Feelings of Isolation Lack of a support system; conflicts with an overseeing organization; feelings that it is a solitary role Costs The potential health and performance cost of psychological stress to sports coaches is significant (Fletcher & Scott, 2010). Manifestations include impacts on physical health; impediments to focus and decisionmaking; difficulties performing necessary task such as strategy, analysis and preparation of athletes; and in extreme cases causes burnout. Physical health issues may include physical illness, loss of sleep, poor eating habits, and decreased immune response. Mental and emotional issues may include emotional outbursts, frustration, anger, loss of confidence, loss of focus and loss of motivation. Research has also identified the issue www.sirc.ca
of “emotional contagion” (Fletcher & Scott, 2010) in the coach-athlete relationship wherein a coach’s emotional state can impact on their athlete’s motivation, self-confidence, and focus. The effect is mirrored on the one side with how the coaches perceive their stress to be affecting their athletes, and on the other side how athletes perceive their coach’s stress to impact on their performance.
in their own time can prevent stress and better enable their coping abilities. Interventions such as these help the coach increase their self-awareness and enhance their resilience to internal and external pressure sources.
Coping While much research has focused on causes of stress in coaching, studies are beginning to examine coping behaviours and mechanisms for coaches specifically. In terms of coping behaviours, most of the stress studies have focused on the athlete’s experience, however, many of the same techniques can be utilized to assist the coach with how they deal with the stressors and strains associated with their jobs. The way a coach expects their athletes to thrive under pressure is much the same way that the coach can thrive under pressure by (Paccagnella, 2005):
Frey, M. (2007). College coaches’ experiences with stress--”problem solvers” have problems, too. Sport Psychologist, 21(1), 38-57.
• striving for excellence rather than perfection, • ensuring the coach is well prepared prior to competition, and • having good error-recovery strategies that don’t affect confidence. Coaches realize that they should recognize and focus on the aspects of situations that they can control, and highlight the process of coaching rather than performance outcomes (Fletcher & Scott, 2010). Elite sport can and should use psychological skills training for coaches as well as athletes focusing on visualization of pressure situations, relaxation training, imagery, and time management skills. Coaches should also be aware of how drawing on social support, maintaining a balanced life and including exercise 23
Bibliography
Fletcher, D., & Scott, M. (2010). Psychological stress in sports coaches: A review of concepts, research, and practice. Journal of Sports Sciences, 28(2), 127-137.
Humphrey, J. H., Yow, D. A., & Bowden, W. W. (2000). Chapter 4: Stress among coaches and athletic directors. Stress in College Athletics, , 49-69. Kulmatycki, L., & Bukowska, K. (2007). Differences in experiencing relaxation by sport coaches in relation to sport type and gender. Human Movement, 8(2), 98-103. McNamara, J. (2006). ‘Bouncing back’ from stress: Resilient coaching. Sports Coach, 29(3), 24-25. Olusoga, P., Butt, J., Hays, K., & Maynard, I. (2009). Stress in elite sports coaching: Identifying stressors. Journal of Applied Sport Psychology, 21(4), 442-459. Paccagnella, M. (2005). Performing under pressure. Sports Coach, 28(1), 12-13. Yow, D. A., Humphrey, J., & Bowden, W. (2000). Coaches under stress: Causes, consequences and coping. Athletics Administration, 35(4), 32-35. Raedeke, T. D. (2004). Coach commitment and burnout: A one-year follow-up. Journal of Applied Sport Psychology, 16(4), 333-349. Tashman, L. S., Tenenbaum, G., & Eklund, R. (2010). The effect of perceived stress on the relationship between perfectionism and burnout in coaches. Anxiety, Stress & Coping, 23(2), 195-212. Thelwell, R., Weston, N. J. V., & Greenlees, I. (2010). Coping with stressors in elite sport: A coach perspective. European Journal of Sport Science, 10(4), 243-253. Yow, D. A., Humphrey, J., & Bowden, W. (2000). Coaches under stress: Causes, consequences and coping. Athletics Administration, 35(4), 32-35.
SIRCuit Volume 1 (2) Fall / automne 2010
From the SIRC Collection When 30,000 articles cross your desk you start to notice trends as well as the research that seems particularly strategic. We are pleased to highlight some of the key articles in various topics that have attracted our attention. Comme nous voyons passer sur nos pupitres près de 30 000 articles, nous avons une bonne idée des tendances et des axes de recherche privilégiés. Nous sommes alors très heureux de mettre en évidence quelques-uns de ces articles provenant de divers champs d’intérêt.
Coaching
Anti-doping
Career development of expert coaches, Christine S. Nash & John Sproule (2009) International Journal of Sports Science & Coaching; 4(1): 121-138.
Elite athletes’ duty to provide information on their whereabouts: Justifiable anti-doping work or an indefensible surveillance regime?, Hanstad, Dag Vidar; Loland, Sigmund, (2009) European Journal of Sport Science, 9(1):3-10.
Feeling Second Best: Elite Women Coaches’ Experiences, Norman, Leanne, (2010) Sociology of Sport Journal, 27(1): 89-104. High performance coaching -- managing a decentralized program/ Entraînement de haut niveau -- gestion d’un programme décentralisé. Scott, S. (2010). Coaches Plan/ Plan Du Coach, 17(1), 18-19.
LTAD ISSP position stand: to sample or to specialize? Seven postulates about youth sport activities that lead to continued participation and elite performance. Côté, Jean; Lidor, Ronnie; Hackfort, Dieter, (2009) International Journal of Sport & Exercise Psychology, 7(1): 7-17. “Specializers” Versus “Samplers” in Youth Sport: Comparing Experiences and Outcomes. Strachan, Leisha; Côté, Jean; Deakin, Janice, (2009) Sport Psychologist, 23(1): 77-92
Injury Prevention The efficacy of cryotherapy on recovery following exercise-induced muscle damage. Burgess, Theresa L.; Lambert, Michael I., (2010) International SportMed Journal, 11(2): 258-277. The International Olympic Committee (IOC) Consensus Statement on periodic health evaluation of elite athletes March 2009. Ljungqvist, Arne; Jenoure, Peter; Engebretsen, Lars; Alonso, Juan Manuel; Bahr, Roald; Clough, Anthony; De Bondt, Guido; Dvorak, Jiri; Maloley, Robert; Matheson, Gordon; Meeuwisse, Willem; Meijboom, Erik; Mountjoy, Margo; Pelliccia, Antonio; Schwellnus, Martin; Sprumont, Dominique; Schamasch, Patrick; Gauthier, Jean-Benoît; Dubi, Christophe; Stupp, Howard, (2009) International SportMed Journal,
Equipping athletes to make informed decisions about performance-enhancing drug use: a constructivist perspective from educational psychology., Hanson, James M., (2009) Sport in Society, 12(3): 394-410.
Psychology Athlete Engagement in Elite Sport: An Exploratory Investigation of Antecedents and Consequences. Hodge, Ken; Lonsdale, Chris; Jackson, Susan A., (2009) Sport Psychologist, 23(2): 186-202. Competition stress in sport performers: Stressors experienced in the competition environment. Mellalieu, Stephen D.; Neil, Richard; Hanton, Sheldon; Fletcher, David, (2009) Journal of Sports Sciences, 27(7): 729-744. What it takes to win: Perspectives from Vancouver 2010/Ce qu’il faut pour gagner : Points de vue sur Vancouver 2010. Werthner, P. (2010). Canadian Journal for Women in Coaching, 10(3), 1-7.
Health & Nutrition What is the optimal composition of an athlete’s diet? Elizabeth M. Broad & Gregory R. Cox, (2008) European Journal of Sport Science, March 2008; 8(2): 57-65. Fueling the Vegetarian (Vegan) Athlete. Fuhrman, Joel; Ferreri, Deana M., (2010) Current Sports Medicine Reports, 9(4), 233-241.
10(3): 124-144.
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Ask SIRC Question: Dear SIRC: Could you provide me with information on exercise-induced asthma? I am coaching an athlete that has been diagnosed with this and I want to learn more about it.
Answer: Thank you for emailing SIRC with your question on Exercise-induced asthma (EIA). There is quite a bit of information on the topic within the SIRC Collection. To get an overview of the topic you can check out the SIRC Newsletter that was published earlier this year where you will find articles on coaching asthmatic athletes, exercise in cold weather, management, training and diagnosis. Additionally you may want to read the World Anti-Doping Association’s Stance on Asthma. In this summary there is a discussion on diagnosis, treatment and medial implications for testing including a best practice treatment.
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Concussions
Please click the images on the right to see previous newsletters or check out our Online Resources. Question: Dear SIRC: I am working with a few athletes who have cut out milk products as they have heard that milk causes mucous/phlegm and therefore believe (as runners) that this could lead to decreased performance. I am looking for any information related to milk products and production of mucous/phlegm and then, if any research has been done on this topic related to athletic performance (male/female).
Periodization
Answer: This question was unique so it was very interesting to see what was available on the topic. Generally we get asked about milk as a recovery beverage and have incorporated into several newsletters that we have done on different beverages and hydration. Several articles are listed below that will help answer your question. Although this appears to be a common perception by athletes there does not seem to be research directly relating to athletes on the topic. Many of the articles appear in medical databases regarding milk and mucus production and relate to children and asthma. The Wüthrich article below is references quite a bit as it looks at previous studies regarding this topic. This article is available in full-text and has 49 bibliographic references listed at the end that may help you continue your search.
Overtraining
If you would like more documents on this topic click here. Wüthrich, Brunello and Alexandra Schmid, Barbara Walther, and Robert Sieber. (2005) Milk Consumption Does Not Lead to Mucus Production or Occurrence of Asthma. Journal of the American College of Nutrition. 24: 547S-555S. (Accessed online: Aug. 4, 2010) www.sirc.ca
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Proactive & Preventative Medicine Récupération à court terme à l’aide des boissons énergétiques par Jonathan Tremblay, Ph.D. Directeur scientifique, Centre National Multisport - Montréal Professeur-adjoint, Département de kinésiologie, Université de Montréal
For Jonathan Tremblay’s bio CLICK HERE
Résumé La capacité qu’a l’athlète de haut niveau à répéter des efforts à une intensité élevée, qu’ils soient reproduits dans une même journée ou lors de plusieurs jours consécutifs, repose grandement sur sa capacité à récupérer. Cette récupération peut être optimisée en ayant recours à différentes méthodes, certaines n’étant pas encore éprouvées. La grande disponibilité des boissons énergétiques commerciales ou de conception artisanale, ainsi que leur efficacité potentielle pour optimiser la récupération leur confèrent un rôle d’importance dans le rituel d’entraînement de l’athlète. Leur consommation, de sorte à en tirer les bénéfices maximaux pour la récupération, doit toutefois respecter certains principes clés. Une boisson énergétique qui permettra à l’athlète d’optimiser sa récupération à court terme devra contenir, au moins, trois principaux ingrédients : un volume d’eau, une certaine quantité d’électrolytes et des glucides. La concentration de la boisson en électrolytes et en glucides, ainsi que le type de glucides, pourront affecter l’absorption de la boisson par le tube digestif, sa capacité à réhydrater et à restaurer les réserves de glycogène musculaire. Il est bien établi que la présence d’une légère déshydratation et/ou de faibles réserves en glycogène musculaire, dans plusieurs sports, peuvent entraîner des réductions significatives de performance. Pour cette raison, une connaissance accrue des mécanismes pouvant influencer la récupération à court terme des athlètes pourra aider l’entraîneur (et l’athlète) à choisir une boisson énergétique qui lui conviendra et lui permettra d’améliorer sa performance à moyen et long terme.
Abstract For the high-performance athlete, the ability to repeat high-intensity bouts of exercise, whether in the same day or on multiple consecutive days, greatly depends on his/her ability to recover. Athletes can rely on a variety of methods to optimize recovery, some having less scientific support than others. The availability of commercial or homemade sport drinks, as well as their potential to optimize recovery, gives them an important role in the athlete’s training regimen. However, key principles need to be respected in order to fully benefit from sport drinks during recovery. To optimize short-term recovery, the typical drink should contain three main ingredients : a volume of water, a certain amount of electrolytes and carbohydrates. The amount of electrolytes and carbohydrates, as well as the type of carbohydrate can greatly affect the absorption of the drink by the gut, its ability to restore hydration status and restore muscle glycogen stores. It is well established that even a relatively low level of dehydration and/or low muscle glycogen stores, in many sports, can have a huge impact on performance. For this reason, a greater knowledge of the mechanisms involved in short-term recovery will allow coaches (and athletes) to be more critical towards their choice of sport drinks, and allow them to choose one that will allow to increase performance in the long run.
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Jonathan Tremblay explains why he wrote this article. CLICK HERE
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ans l’entraînement du qu’elle est nécessaire pour provoquer des adaptations sportif de haut niveau, repose en partie sur sa capacité de récupérer entre chacun l’imposition d’une des stimuli. Cette récupération est toutefois difficile à charge d’entraînement menant définir puisqu’elle peut être interprétée soit par un effet à un déséquilibre homéostatique direct sur l’expression de paramètres physiologiques est chose courante. En fait, au repos ou pendant l’effort, ou encore sur la capacité à ce stress est nécessaire pour reproduire une performance subséquente. Une multitude mener à des adaptations de de méthodes peuvent être mises de l’avant pour optimiser nature physiologique ou autre, la récupération, certaines pouvant parfois relever de qui permettront à l’athlète l’ésotérisme, d’autres étant supportées par des évidences d’améliorer sa performance solides et ayant fait leurs preuves. Une de ces méthodes, qui à moyen et long terme. La est maintenant indéniablement reconnue pour contribuer capacité de l’athlète à supporter de manière significative à la récupération de l’athlète, une charge d’entraînement telle vient de l’optimisation de la nutrition en période post26
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exercice. Les boissons énergétiques, étant principalement composées de glucides, d’électrolytes et d’un volume de liquide, constituent un outil très intéressant pour favoriser la récupération à court terme de l’athlète puisqu’elles peuvent contribuer à la récupération par trois principaux mécanismes : la réhydratation, le remplacement des pertes électrolytiques et la resynthèse de glycogène musculaire. En conséquence, il est non souhaitable d’amorcer une La déshydratation et la réhydratation Une quantité importante de liquide peut être perdue au période d’exercice avec un déficit en liquide résultant d’une cours de l’exercice, pouvant parfois atteindre jusqu’à réhydratation inadéquate à la suite de l’effort précédent. 3 litres par heure d’effort soutenu. Plusieurs facteurs Chez l’athlète en santé, le remplacement quotidien des peuvent avoir une influence sur ces pertes, dont le niveau pertes de liquides et le maintien de la balance hydrique sont d’hydratation initiale, la température externe, l’humidité bien régulés par la sensation de soif et les pertes d’urine. Dans des conditions de relative, certains facteurs stress (comme l’exercice, génétiques, etc. Si l’athlète ...Une quantité importante de un environnement chaud ou n’ingère pas suffisamment liquide peut être perdue au froid, l’altitude), la soif n’est de liquide pendant l’effort cours de l’exercice, pouvant peut-être pas un stimulus pour remplacer les pertes, ce parfois atteindre jusqu’à suffisant pour maintenir un qui est fréquemment le cas, statut d’hydratation stable. un déficit s’en suivra à la 3 litres par heure d’effort fin de la période d’exercice. soutenu. Les études rapportant Ce déficit pourra facilement l’ingestion volontaire de s’observer par une perte de masse corporelle qui donnera une bonne idée des pertes de liquides dans plusieurs disciplines sportives montrent que liquides encourues. Ces pertes peuvent, dans certains cas, les athlètes remplacent seulement environ 30-70% des avoir des effets délétères sur la performance, la régulation pertes de sueur encourues pendant l’effort (figure 1; ACSM de la température corporelle (thermorégulation) et les 2007). Chez la plupart des athlètes, on peut donc s’attendre fonctions cognitives (Cian et coll. 2000), particulièrement à observer un niveau de déshydratation léger à modéré à la si l’effort est effectué dans un environnement chaud. Une fin de l’entraînement ou de la compétition. Après l’effort, réduction de la performance peut être détectée à partir même lorsque des liquides sont facilement accessibles, les d’un déficit liquidien de 1.8% de la masse corporelle, mais athlètes ne boivent pas un volume suffisamment important cette réduction progresse toutefois avec l’ampleur de la pour leur permettre de se retrouver en balance hydrique. Le déficit en liquide peut alors persister pendant une période déshydratation (ACSM 2007). prolongée surtout si l’athlète continue de perdre des liquides par sudation, mais principalement par l’excrétion urinaire. Le succès de la stratégie de réhydratation postexercice dépendra ultimement de la balance entre les liquides ingérés et les pertes d’urine. Idéalement, l’athlète devrait viser une récupération complète des pertes de liquides encourues entre les périodes d’exercice de sorte à entreprendre un nouvel effort en balance hydrique. Ceci peut-être difficile si des pertes de liquides importantes ont été encourues pendant l’effort (correspondant à ~2-5% de la masse corporelle) et que la durée de récupération avant le prochain effort est inférieure à 6-8 heures. La palatabilité et le contenu en électrolytes des boissons énergétiques leur confèrent alors un rôle de choix pour la restauration de la Figure 1 - Perte de liquides sous forme de sueur et volume ingéré sur une base balance hydrique après une période d’exercice exténuante.
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volontaire des athlètes pratiquant différents sports, à l’entraînement ou en compétition. Données recueillies à partir de la prise de position sur l’ingestion de liquides pendant l’exercice de l’ACSM (2007).
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Plusieurs études ont montré que la palatabilité des liquides pouvait avoir un effet considérable sur l’ingestion volontaire de liquide; la qualité, la saveur et la température étant identifiées comme les variables les plus importantes (voir la prise de position de l’ACSM [2007] pour une revue). Dans une recension récente des écrits, Burdon et coll. (2010) rapportent quatre études dans lesquelles une amélioration de la performance de 10% était observée avec l’ingestion de boissons froides pendant l’effort. Les résultats ne sont toutefois pas unanimes et on ne peut conclure sur la température idéale d’une boisson ingérée pendant ou après l’effort. Quoiqu’en général, l’ingestion d’eau à une température très faible (0°C) peut paraître plus apaisante, l’eau fraîche (15°C) peut être consommée en plus grande quantité et donc mieux réhydrater l’athlète qui en a besoin. Quelques études rapportent aussi une ingestion plus importante de liquides en récupération avec des boissons sucrées qu’avec de l’eau seule, ce qui suggère que le goût ou la saveur de la boisson peut également contribuer à favoriser l’ingestion de liquides. Par exemple, Carter et Gisolfi (1989) ont observé l’ingestion volontaire de liquides au cours de la récupération, après une période d’exercice prolongée sur vélo stationnaire menant à un déficit hydrique correspondant à 2% de la masse corporelle. Ils ont rapporté une ingestion de liquide beaucoup plus grande lorsque l’on présentait aux sujets une boisson contenant des glucides et des électrolytes que lorsqu’on leur fournissait simplement de l’eau. L’ingestion d’eau mena au remplacement de 63% des pertes de sueurs alors que la boisson sucrée à un remplacement de 79% des pertes. Cet aspect soulève l’importance de trouver une boisson énergétique dont le goût est apprécié des athlètes, ce qui favorisera l’ingestion volontaire. Sans oublier que, pour un même athlète, le goût recherché dans une boisson de réhydratation pourra varier selon les conditions environnementales et le niveau de déshydratation. Le remplacement des électrolytes perdus Les entraîneurs savent bien que les athlètes doivent bien s’hydrater pendant et après l’exercice et les recommandations qu’ils font aux athlètes qu’ils entraînent vont dans ce sens. Toutefois, comme dans la plupart des situations où les athlètes doivent s’hydrater ou se réhydrater, ils ingèrent de l’eau seule, ne contenant pas ou très peu d’électrolytes, ce qui ne permet pas d’optimiser la récupération du statut hydrique à la suite d’une période d’exercice. En effet, l’ingestion d’eau seule entraîne www.sirc.ca
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Figure 2 - Effet de la concentration en sodium de la boisson ingérée sur la rétention des liquides en récupération. La déshydratation provoquée par la période d’exercice épuisant est compensée par la réhydratation à la fin de l’exercice. Celle-ci restitue le niveau d’hydratation au-delà du niveau d’hydratation initial, mais ce statut est maintenu en balance positive seulement avec lorsque la boisson contenant une concentration élevée de sodium (23 g/L) est ingérée. Figure adaptée de Shirreffs & Maughan (1998).
une dilution de la concentration plasmatique en sodium, ayant pour conséquence une réduction de la sensation de soif et une augmentation de la production d’urine. Une étude de Shirreffs et Maughan (1998) permet de bien illustrer ce phénomène (figure 2). Ceux-ci ont provoqué une déshydratation correspondant à 2% de la masse corporelle chez des sujets qui effectuaient un effort dans un environnement chaud, ils ont maintenu ces derniers en observation pendant une période de six heures après leur avoir administré un volume de boissons, contenant différentes concentrations de sodium, correspondant à 150% des pertes de liquides encourues. Les auteurs ont pu observer une meilleure rétention des liquides en fonction de la concentration en sodium de la boisson. La production d’urine était significativement plus élevée pour les boissons sans et avec une faible concentration de sodium (5.75 g/L) que pour les boissons avec des concentrations plus élevées (11.5 et 23 g/L). Après les six heures de récupération, l’excrétion urinaire des sujets ayant ingéré la boisson sans sodium était plus élevée de 600 mL que pour les sujets qui avaient ingéré la boisson avec une concentration élevée (23 g/L). La balance hydrique fut atteinte à la fin de la période de récupération lorsque les boissons avec des concentrations élevées étaient ingérées, alors que les sujets ayant ingéré les boissons contenant une plus faible concentration était toujours en balance négative, et ce, même après avoir ingéré un volume correspondant à 150% des pertes en sueur. Il n’y a pas de consensus en qui a trait à la concentration de sodium optimale que l’on devrait retrouver dans une boisson de récupération. Les pertes en sodium dans la sueur varient grandement entre les sujets, les concentrations typiques variant typiquement entre 5-18 g par litre de SIRCuit Volume 1 (2) Fall / automne 2010
sueur (Armstrong et coll. 1987). Si le but est remplacé les pertes, une concentration moyenne de sodium de ~12 g/L dans une boisson de récupération pourrait donc être très bien justifiée, ne connaissant pas les pertes réelles de sodium par la sueur. Toutefois, de sorte à être plus agréables au palais et à susciter un intérêt commercial pour un usage à grand public, les boissons énergétiques contiennent généralement une quantité plus modérée de sodium (2-6 g/L). Pour un usage général, la palatabilité (affectant l’ingestion volontaire) et le contenu en sodium (affectant la rétention des liquides) sont importants. Un plus grand volume d’une boisson énergétique pourra être ingéré sur une base volontaire si la palatabilité est élevée, mais une boisson ayant une concentration en sodium plus élevée, qui peut réduire la palatabilité, favorisera davantage la rétention des liquides. Dans un but de réhydratation, l’efficacité des formulations populaires de boissons énergétiques, contenant une concentration modérée de sodium, semble meilleure que l’eau seule, mais pas optimale. Les boissons énergétiques commerciales ont généralement une meilleure palatabilité et leur concentration modérée en sodium permet une meilleure rétention des liquides que l’eau seule. Néanmoins, si l’objectif est de maximiser la rétention des liquides, l’augmentation de la concentration en sodium au-delà des valeurs typiquement observées dans ce genre de boissons pourrait s’avérer judicieuse (Shirreffs & Maughan 1998).
La resynthèse de glycogène musculaire Le glycogène musculaire constitue la principale source d’énergie au cours de l’effort prolongé à une intensité modérée à élevée (Romijn et coll. 1993). La restauration des réserves de glycogène à la suite d’une période d’exercice épuisante est probablement un des facteurs déterminants de la récupération et de la durée (Jentjens et Jeukendrup 2003). Selon l’importance de la déplétion des réserves et étant donné qu’une quantité suffisante de glucides est ingérée, la restauration complète des réserves de glycogène peut s’effectuer dans un délai de 24 heures (Casey et coll. 1995). Plusieurs études rapportent les interventions nutritionnelles permettant d’atteindre une surcompensation des réserves de glycogène musculaire en préparation à une compétition, mais ces procédures ne résolvent pas le problème associé aux évènements qui exigent une resynthèse rapide du glycogène musculaire dans un court laps de temps. Les athlètes peuvent parfois avoir plusieurs épreuves dans la même journée rendant plus difficile la restauration complète des réserves de glycogène. Les boissons énergétiques, étant composées de glucides simples ou d’un mélange de ceux-ci, peuvent s’avérer un outil de taille pour la récupération, particulièrement dans les minutes qui suivent l’exercice.
La période de récupération post-exercice est caractérisée par une augmentation de la captation de glucose par le muscle, qui s’effectue initialement par un mécanisme ne dépendant pas de l’insuline (hormone favorisant l’entrée de glucose, entre autres, dans les tissus). Par la suite, une sensibilité accrue à l’insuline permet une entrée additionnelle de glucose dans le muscle (Jentjens et Jeukendrup 2003). C’est la translocation des transporteurs Les boissons énergétiques populaires contiennent presque de glucose (GLUT4) vers la surface de la cellule toutes une certaine quantité de potassium en plus du musculaire qui permet l’entrée de glucose dans le muscle. sodium. Le potassium semble également efficace pour Une série de réactions biochimiques permettront ensuite favoriser la rétention à cette molécule de ...Les boissons énergétiques, des liquides ingérés en glucose de s’agréger étant composées de glucides récupération. Toutefois, au glycogène. La simples ou d’un mélange de l’ajout de potassium n’a présence des protéines pas d’effet additif sur de transport du glucose ceux-ci, peuvent s’avérer un outil une boisson contenant ainsi que l’activité de taille pour la récupération, déjà du sodium et le enzymatique accrue en particulièrement dans les minutes remplacement de ce période post-exercice qui suivent l’exercice. dernier semble la priorité laissent entrouverte puisque les pertes dans une fenêtre temporelle la sueur peuvent être importantes. En outre, il n’y a pas de pendant laquelle les conditions permettant une resynthèse justification convaincante supportant l’addition d’autres de glycogène musculaire sont optimales. La disponibilité électrolytes, tels que le magnésium ou autre, dans les des glucides au moment opportun de la récupération est boissons de récupération. donc critique pour restaurer les réserves de glycogène. Notamment, il est possible de restituer les réserves en
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deçà du niveau pré-exercice lorsque des glucides sont de glucides par kg de masse corporelle (figure 4). consommés très rapidement après l’exercice (Ivy 2001). Cette fenêtre temporelle est toutefois éphémère de telle Une augmentation de l’absorption des glucides par le tube sorte que le taux de resynthèse est réduit de manière digestif pourrait repousser l’atteinte de ce plateau dans significative si l’ingestion est retardée plus de deux heures la synthèse de glycogène musculaire. Le glucose qui est (figure 3). ingéré et se rend dans le tube digestif est absorbé et migre ainsi vers la circulation. Ce transport du tube digestif à la circulation requiert, comme pour dans le muscle, certains transporteurs (différents de ceux du muscle). Ces transporteurs sont spécifiques à la molécule qui est transportée et donc, différents transporteurs facilitent le transport du glucose et du fructose par exemple, deux monosaccharides (ou glucides simples). En combinant deux types de glucides dans une même ingestion, Currell et coll. (2008) ont montré que l’absorption des glucides pouvait en effet être accrue, ainsi que la disponibilité des glucides. On peut donc croire que la combinaison de différents types de glucides simples, facilement absorbables, permettrait d’accroître la disponibilité des glucides et, en conséquence, la synthèse de glycogène musculaire en récupération. L’équation n’est toutefois pas aussi simple, d’autres facteurs affectant la synthèse de glycogène restent à être élucidés, mais la combinaison de différents glucides semble une avenue intéressante. Les boissons énergétiques ne sont qu’une partie de la
Figure 3 - La capacité du muscle à resynthétiser le glycogène musculaire est beaucoup plus grande immédiatement après l’effort. À ce moment, les conditions sont optimales pour le transport du glucose circulant vers le muscle, permettant ainsi la synthèse rapide de glycogène. On observe une réduction importante du taux de synthèse après 90 minutes, avec ou sans ingestion de glucides pendant la récupération. L’ingestion de glucides augmente grandement la disponibilité de ceux-ci qui accélère grandement la synthèse de glycogène. Figure adaptée de van Hall et coll. (2000).
Comme mentionné ci-haut, un des facteurs limitant la resynthèse du glycogène musculaire constitue la disponibilité des glucides. Il est logique de penser que plus la quantité de glucides disponible en circulation est grande, plus le muscle a le potentiel de capter le glucose afin de fabriquer du glycogène. On pourrait croire que la resynthèse de glycogène musculaire est donc limitée par la capacité à ingérer des glucides, et que plus la dose de glucides ingérée est grande, plus la synthèse sera importante, mais ce n’est pas le cas. Jentjens et Jeukendrup (2003) ont effectué une recension des écrits sur les facteurs affectant la resynthèse de glycogène musculaire après l’effort et ils ont pu constater, en effet, que l’ingestion d’une dose modérée de glucides en récupération était fortement reliée avec le taux de synthèse du glycogène, mais qu’un plateau était atteint autour d’un taux d’ingestion de 1.2g www.sirc.ca
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Figure 4 - Le taux de synthèse du glycogène musculaire après un effort épuisant est fortement relié à la dose de glucides ingérée en récupération. Le taux de synthèse maximal pouvant être atteint semble plafonner autour d’une dose de glucides ingérée correspondant à 1.2 à 1.5 g/h/kg. Figure adaptée de Jentjens & Jeukendrup (2003), dans laquelle les résultats de plusieurs études sont compilés.
récupération La récupération de l’athlète doit faire partie intégrante de la planification de l’entraînement. Il faut se rappeler que SIRCuit Volume 1 (2) Fall / automne 2010
les adaptations physiologiques, quelles qu’elles soient, ne se produisent pas pendant l’entraînement, mais bien pendant le repos qui le suit. Les boissons énergétiques sont intéressantes principalement dans les minutes qui suivent l’exercice ou encore entre des efforts intermittents ou la récupération doit se faire rapidement. En réhydratant, en fournissant des électrolytes et des glucides qui permettront d’absorber les liquides plus rapidement et de resynthétiser le glycogène musculaire, les boissons énergétiques constituent un outil de choix pour optimiser la récupération de l’athlète. De pair avec une alimentation équilibrée, il est toujours suggéré de consulter une nutritionniste du sport afin d’identifier la boisson qui conviendra le mieux aux besoins et à la situation de l’athlète. ∆
Jonathan Tremblay asks the question “What’s next?” CLICK HERE
For references, click here
Ingrédients d’une boisson de récupération “idéale”
• 1 à 1.5 L d’eau par kg de masse corporelle perdue pendant l’effort. • 1.2 à 1.5 g par kg de masse corporelle de glucides simples (monosaccharides). • Mélanger plusieurs glucides (glucose, fructose, saccharose, etc.) pour favoriser l’absorption intestinale. Maintenir la proportion du glucose toujours 2 à 3 fois supérieure aux autres glucides (ex.: pour une boisson contenant 90g de glucides : 60g de glucose + 20g de fructose + 10g de saccharose). • Ces glucides peuvent être composés de glucides complexes (polysaccharides, comme la maltodextrine par exemple) si la période de récupération est de plus d’une heure. • 1-1.5g de sodium par litre de solution. Il faut se rappeler, plus la boisson sera riche en sodium, plus la rétention en eau sera efficace, au détriment de la palatabilité de la boisson.
Did you know... Unless they’re fortified, most sports drinks lack the vitamins, minerals and protein you find in chocolate milk. Protein is especially important post training, since it helps enhance recovery by repairing damaged muscle tissue and promoting muscle growth. www.rechargewithmilk.ca
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SIRCuit Volume 1 (2) Fall / automne 2010