Thermal stress in open water swimming Thermal stress in open water swimming : estabilishing competition parameters for athlete safety Research Project IOC/FINA/ITU & Otago University (NZ) S. Migliorini, M. Mountjoy, D. Gerrard
Aquatic Enviroment Health Risks
• • • • • •
Flora & Fauna Current & waves & waves Pollution : air & water W Water quality li Wind and air temperature p Water temperature hyperthermia & hypothermia
Rationale for Project for Project While we have a good understanding of the effect of cold‐water immersion, there is no research that specifically addresses the question of heat stress in open water swimming.
Other IFs such as IAAF have competition criteria and safety guidelines for the prevention and the treatment of heat related disorders : IAAF recommended cancelling or rescheduling races if WGBT is above 28°C. (Enviromental influencing human performance IAAF Medical d l Manuall)
Olympic Movement Medical Code According to the Olympic Movement Medical Code the International Sports Federations are tasked to evaluate competition venues and climates in which their athletes train and compete and subquently develop guidelines to safeguard and compete and subquently to safeguard athlete health by minimizing the risk arising from potentially dangerous enviromental conditions. The legal system requires IFs and race organizers to produce a safe event and to identify and disclose all the know risks to the athletes.
Rationale for Research Project 1) To prevent the fatalities p and armonize the IF rules 2)) To improve
Rationale for Project
To prevent the fatalities. h f l • SSudden dd death d h in marathon swim i h i : elite li USA swimmer USA i FINA 10 k FINA 10 km World Cup, UAE, 2010 (air T° 35C, water T° 29C). • Sudden death in triathlon : most of them during the swim leg (30 out of 38 non traumatic athlete death between 2003 /2011 USAT fatality Incidents study). • Data derived from FINA Medical Reports from the FINA Marathon and GP Circuits in open water swimming and GP Circuits in open water swimming show that show that athletes have required treatment for exertional heat illness when competing in warm enviroments. • Data derived from ITU Medical Reports show that exertional muscle cramping, heat exhaustion and exertional heat illness are prevalent in many in many Triathlon events. Triathlon events
Rationale for Project
T i To improve and armonize d i the rules. h l • FINA. Water temperature at FINA sanctioned events range from a minimum of 16°C up to 31°C. The use of wetsuit is forbidden. forbidden • Notably, current FINA rules stipulate a minimum water temperature but the Federation temperature, but the Federation is yet to establish to establish a firm a firm upper limit providing only a recommended limit of 31°C for FINA events. • ITU. Water temperature at ITU sanctioned events starts from a minimum of 13°C (1500m) or 14° (3000m‐4000m), but the Federation did not reccomend an upper temperature limit. Th The wetsuit t it use is i allowed ll d following f ll i the ITU rules. th ITU l
Open water swimming competitions While there Whil th i no upper limit is li it for water temperatures f t t t enforced f d by these organisations, it is not uncommon for events to be p of 30‐32° C in locations around held in water temperatures South‐East China, the Middle East and Central America. This can be accompanied by ambient temperatures of 35‐40° C and relative humidity of 50‐70%.
Research Needs • Determination of safe upper limit water temperature for training and competitions (core body temperature and performance capacity)
• Determining the influence of other enviromental factors (high‐ low air temperature,humidity p , y)). • Determining optimal strategies to better acclimatize athletes. • Identify de t y object objectivee ssigns g so of developing de e op g eexertional e t o a heat eat illness. ess • Determining the validity of self‐perceived body temperature. to and heat • Quantifying factors affecting athlete adaptation to and heat tolerance in water (inflammatory status) • Studyy on thermal p parameters with the use of a wetsuit in hot ambient temperature.
C ll b Collaboration Logistics i i i Identification of the Project Concept. of the Project Concept Agreement of collaboration. Determination of a timeline. of a timeline Arrangement of financial logistics. Agreement of pubblication and Agreement of pubblication and dissemination protocol.
THERMAL STRESS IN OPEN WATER SWIMMING Establishing competition parameters f for competition safety ii f
Methodology • Range of distance (1.5 to10km) and water temperature of most interest to FINA, ITU and IOC in open‐water swimming. to FINA ITU and IOC in open water swimming • Predetermined timed swims of 20, 60 and 120 min. with 3 water temperatures of 20 water temperatures of 20°,27 27° and 32 and 32° C, with warm C with warm and and humid air (ambient temperature 30°C, 50‐70% relative humidity) and full radiant heat loading. • Radiant heat load needed to be incorporated with the heat stressful water temperatures, because of the additional heat load at low latitudes and the prone posture of swimming. • High calibre swimmers and triathletes have been recruited f from Dunedin’s D di ’ elite li swim i squad, supplemented d l d with national ih i l open water swimmers.
Flume in use Swimmer’s stroke is recorded from four cameras (side, above, front , rear). Viewing panels in the side are used for filming and communication.
Illustration of halogen of halogen heat lamps mounted 1.5 m above the swimmer to replicate radiant heat load.
Field Analysis FINA OWS Marathon Series 10 km FINA OWS Marathon Series 10 km
Hong Kong Hong Kong Shantou CHN October 2012
Protocol and Measurements and Measurements • 24 24 swimmers swimmers undertoook a total a total of 190 self‐paced of 190 self paced performance trial in water temperature of 20,27,32°C, with exposure durations (20‐120 min) corrisponding to distance of 1.5km to 10km races (air T° closely the respective water T°, relative humidity 50‐70%, radiant heat load). • All trials are being trials are being undertaken ndertaken in the swimming in the s imming flume fl me where here water temperature can be controlled between 9° and 35°C. are instructed to swim to swim as fast as fast as possible because • Swimmers are instructed this maximises validity by maximising rate of heat production. • Swimming technique, stroke, velocity and distance are recordered continuosly. • Swimmers are monitored for thermal, cardiovascular, psychophysical function throughout all swims. swims
Protocol and Measurements • Core temperature : monitored and recorded continuosly during all swims using a flexible, sterile and disposable a flexible sterile and disposable rectal thermistor. • Heart rate : frequency of ventricular depolarization as detected from R‐R intervals from a chest strap with transmitter. • Blood measures Blood measures : blood : blood glucose, lactate, haematocrit, glucose lactate haematocrit haemoglobin concentrations, are measured before and immediately upon each swim. Plasma concentrations of inflammatory cytokines and antiflammatory cytokines and other humoral factors . • Swimmer Swimmer’ss perception : thermal : thermal disconfort, body disconfort body temperature, exertion, feeling state, are recorded using validate scales. • Swimming fitness and Anthropometry
Preliminary Results • In 190 swims trials (100 conducted in water temperatures of 30°C or warmer) only 5% resulted in core (rectal) temperatures hi h than higher h 39.0°C, the highest 39 0°C h hi h being b i 39.55°C. 39 55°C •
One female partecipant during the 2012 FINA OWS 10 km in Hong Kong had a high starting Tc peaked at 40 a high starting 40°C C (intestinal (intestinal pill thermometry). Water 27.2 thermometry). Water 27.2°C, C, Ambient 27‐31°C, Humidity 73%
• No athletes were removed or voluntarily stopped due to discomfort, distress in the warm water swims. • 4/8 swimmers (50%) did not complete the longer (1 or 2 h) swim in 20°C water. One athlete did not tolerate more than 20 min in 20 C and three 20°C and three others were either stopped due to Tc due to Tc dropping to 35 to 35°C C or or voluntary stopped due to extreme disconfort.
• Potential safetyy p problems in cool water due to autonomic nervous system conflict in open water swimming competition.
Preliminary Results Preliminary Results • No swimmers became distressed or excessively hypherthermic in any of the warm water swims, making it difficult to determine predictive behaviours. • Positive relationships were evident between the core t temperature and perceived t d i d body temperature b d t t (th (thermal l sensation ti and disconfort), which indicated that swimmers can accurately perceive changes in body temperature while swimming in warm water, reducing exercise intensity to limit hyperthermia in racing.
• SSwimmer’s i ’ perceptions, distance ti di t swum, and actual d t l core temperature responses to swimming were unaffected by the imposition of a large increase of a large increase in training load in training load (5 days (5 days of heavily of heavily increased training volume >50%)
38.8 38.6
Meaan Core Temperature (°C)
38.4 38.2 38.0 37.8
32 deg 20 min
37.6
32 deg 60 min 32 deg 120 min
37.4 37 2 37.2 0
10
20
30
40
50
60 Time (min)
70
80
90
100
110
120
Mean core temperature responses during 3 swim distances in 32°C water temperature with climatic heat stress.
Sweating rate and dehydratation Sweating rate and dehydratation in hot water Even in water, where the ability to evaporate is greatly reduced and the skin remain wetted our swimmers showed reduced and the skin remain wetted, our swimmers showed sweat rates and dehydration not dissimilar to those observed in terrestrial athletes (i.e.marathon ) in terrestrial athletes ((i.e.marathon runners). Normal sweating during swimming is encouraged by maintaining regular fluid loading fluid loading. Swim Condition d
% Net Fluid Body Mass d Consumed d Loss (L)
Gross Fluid Loss (L) ( )
Rate of fluid l loss (L.h‐1)
32°C, 20 min
0.91 ± 0.44
0.38 ± 0.20
0.80 ± 0.33
2.39 ± 0.91
32°C, 60 min
0.93 ± 0.79
0.54 ± 0.19
1.20 ± 0.60
1.20 ± 0.60
32°C, 120 min
1.84 ± 1.49
1.03 ± 0.53
2.35 ± 1.29
1.18 ± 0.64
Recommendations • Because no intollerance no intollerance or unusually or unusually high exercising high exercising core core temperature were observed in maximal effort swims in 30‐32°C p are to considered safe. water T°such temperatures • Potential variability in physiological responses to thermal stress exists between swimmers subjected to lab test versus the race enviroment. • We recommended a more conservative limit, perhaps 31°C, because swimming in open‐water competition might produce hi h Tc higher T than h is i produced d d in lab trials. i l b i l • There is a potential safety problem with open‐water swimming competitions in cool water especially in cool water especially relevant for lean for lean swimmers. swimmers
It will be never be possible to agree upon a finite water temperature at wich the safety of every athetes can be guaranteed under every circumstance. No specific measure, scale or specific temperature will be a surrogate for the combined vigilance of race officals, medical staff, coaches , athlete support staff and of a correct t ff d f t medical di l plan. l
Mayy 2013 : Conclusion of the Research Project IOC/FINA/ITU