5 must-read research reviews on injury prevention & rehab by Science for Sport

SPECIAL EDITION 5 must-read research reviews on injury prevention & rehab

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Page Number

Section

Link to Abstract Review Title

Study Details

Practical Takeaways from study

Related links to learn more about the topic

Reviewers comments on the study

Strength & Conditioning

[Abstract]

Hamstring strength vs. length: what should be the recovery priority following hamstring injury? OBJECTIVE

WHAT THEY DID

WHAT THEY FOUND

Most acute hamstring strains which occur during sprinting involve the long head of the biceps femoris (BFlh) and the known risk factors for hamstring strain include age, strength deficits, flexibility, and fatigue. Additionally, a history of hamstring strains is a strong predictor. As such, it is necessary to investigate if there are activation deficits of the hamstring muscles and alternations in kinematics during maximum effort sprinting when hamstring strain has occurred.

For the purposes of this study, a hamstring strain was defined as an acute pain that was sustained during training or competition that prevents the player from participating in training or competition for at least a week. The time period after injury ranged from 2-61 months, with 1-6 months taken to return-to-sport of ten male college sprinters (age = 19.9 ± 0.3 yr) with a history of unilateral hamstring strain injuries.

The key findings of this study included:

Each participant performed a maximal effort sprint with passive markers and electrodes attached to their body to provide 3D kinematic data and EMG of the BFlh and Gmax muscles. After the sprinting trial, concentric strength assessments of bilateral hip and knee flexors and extensors were performed on a Cybex Isokinetic Dynamometer. Three consecutive maximum voluntary contractions were performed at velocities of 60°/s and 180°/s with 30 sec rest between sets.

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Therefore, this study investigated the EMG activity of the BFlh and gluteus maximus (Gmax) muscles and the kinematic characteristics during overground sprinting in track athletes who had returned to sport following hamstring strain.

Practical Takeaways The inter-limb difference observed in this study may reflect a shorter optimal fibre length of the previously injured hamstring muscles, indicating the BFlh had not fully recovered completely despite rehabilitation. Additionally, previous research has shown significantly lower eccentric knee flexion torque in the extended knee position (see HERE). This might suggest the importance of evaluating the function of the hamstring muscles, particularly during eccentric contraction in the lengthened position. However, this is often not possible in sporting environments due to time and budget. Perhaps taking an interventional approach as in this case study (see HERE), where the weaker leg was targeted through extra hip extension work 3x/week for 6 weeks. Instead of targeting exclusively hip extension, the focus could be shifted towards eccentric hamstring contractions at long muscle lengths. For example, you could add 2x/week focused training as such: Day 1: “Strength” Emphasis: A1) Single Leg Romanian Deadlift 3-4x6-9. B1) Single Leg Isometric Hamstring “Bosch” 3-4x5+5+5 sec.

Day 2: “Velocity” Emphasis: A1) Alex Natera style cable 45° knee flexion performed with rapid ECC/ CON 3-4x5-8 (see HERE). B1) Single Leg Drop Catch Back Extension 3-4x3-6 (see HERE).

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Mean sprinting velocity was 9.39 ± 0.17 m .s-1. No significant inter-limb differences were found in concentric strength.

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During late swing phase, the activity of the BFlh in the previously injured leg was significantly lower than that in the uninjured limb. Significant inter-limb differences were not noted in the Gmax muscle activation.

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Knee flexion angle was significantly higher in the previously injured leg than the uninjured leg at 78 -82% of the sprinting gait cycle (one stride, late swing phase).

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The BFlh length demonstrated significant reduction in the previously injured limb compared to the uninjured limb during late swing phase, while hip and knee torque during the sprinting gait cycle demonstrated no significant differences between limbs.

James’ Comments “Even though the exact location of the hamstring strains could not be identified, all of the participants showed decreased BFlh muscle activity which suggests that most sprinting type hamstring strains occur in the BFlh. Interestingly, concentric strength was not affected by previous injury, though running kinematics were. This may provide practitioners with improved rehabilitation strategies to effectively reduce the risk of re-injury. Whether these particular athletes were more prone to injury is difficult to assess as they had a range of 2-61 months since their injury. Perhaps the sprinting itself, regardless of the altered kinematics acted as a potential vaccine to hamstring re-injury”.

Injury Prevention & Rehab

[Abstract]

How to implement strength and power training principles into rehabilitation OBJECTIVE

WHAT THEY DID

WHAT THEY FOUND

Injuries in sport have a huge impact on athletic performance. It is extremely important to know about previous injury history in rehabilitation because this can potentially increase the risk of re-injury. Questions arise as to whether current rehabilitation programs are sufficient and effective to safely return athletes to performance, in addition to whether there are deficiencies in the sports performance and return-toplay phase that could potentially subject athletes to future injury.

This article examined the available literature in regards to principles of strength training, as well as force and power development, and how these can be implemented in a rehabilitation program.

The key findings in this study were:

This article aims to provide guidance to rehabilitation practitioners and present the available literature pertaining to strength and power development, as well as, how these principles can be incorporated into a rehabilitation program and improve the return-to-sport (RTS) process.

Practical applications were presented and further broke down deficits seen in athletes after injury, including strength, rate of force development, and reactive strength. Evidence based strategies were outlined to address the aspects that can be used to enhance a rehabilitation program, as well as reduce the risk of recurrence of injury.

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Being able to maintain a high level of strength can reduce sports-related injuries by one third and overuse injuries by almost half. Deficits in rate of force development (RFD) have been shown after injury, and the ability to apply high forces in short time frames is imperative to restore from a rehabilitation and performance standpoint when returning athletes to sport.

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In the rehabilitation setting, patients should be gradually progressed to heavier loads in a periodised manner.

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The goal of a rehabilitation program should be to continually challenge the athlete in order to evoke a positive training adaptation.

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Strong communication skills and cooperation with all sports medicine staff is essential to bridge the gap from rehabilitation to performance.

Practical Takeaways  Strength, rate of force development, and reactive strength decrease following an injury, so it is imperative to address all aspects prior to returning an athlete to sport.

 Athletes who are stronger and faster have a lower injury risk than their weaker counterparts.

 Maximal strength training should involve a load (or intensity) of 80%-100% of 1RM utilising approximately 1-6 repetitions across 3-5 sets, with rest periods of 3-5 min and a frequency of 2-3 times per week.

 Medicine-ball throws, plyometrics, and Olympic weight lifting, are all examples of exercise modes to increase RFD.

 Training exercises like drop jumps, depth jumps, rebound sprinting actions, and hurdle jumps can be utilised to target reactive strength.

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Jordan’s Comments “This article shows us the importance of adopting S&C principles in the rehabilitation setting in order to successfully return athletes to sport, with a decreased risk of subsequent injury. Current research shows that 66% of sports-related injuries can be prevented by being strong. With the high percentage of re-injury in many sports across various diagnoses, it makes me question how effective our rehabilitation programs are and to what extent they are progressed prior to RTS. As a strength coach and as a physical therapist, I make it a staple to always progress my athletes program across the entire continuum by varying sets, rep ranges, and increasing load over time to ensure they are truly adapting to allow them to be able to fully handle the demands that will be placed upon them during sport.”

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Injury Prevention & Rehab

[Abstract]

Implementation of an adductor strengthening program in sub-elite football players OBJECTIVE

WHAT THEY DID

WHAT THEY FOUND

Groin-related injuries represent a significant problem in male football, accounting for 4-19% of all time-loss injuries. At the elite level, groin-related injuries occur in 14-17% of all players. The most recent preventative measure to help reduce the reoccurrence of groinrelated injuries, the Adductor Strengthening program consists of a single exercise program based on the Copenhagen Adduction exercise which has shown to reduce the risk of groin problems among male football players by 41%.

During the last weeks of the 2016 season, all 34 teams (632 players) from the Norwegian semiprofessional football league were invited to complete a survey which focused on the implementation and effect of the Adductor Strengthening programme, based on the different dimensions of RE-AIM framework (this included Reach, Efficacy, Adoption, Implementation, and Maintenance).

The key findings of the survey were:

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This study looked at the implementation of the Adductor Strengthening Programme and what player’s beliefs were towards groin injury prevention.

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Prevention of groin injuries was considered at least moderately important by 95.5% of the players. However, when asked about their attitude towards preventative measures, only 50.1% of the players were positive. Strengthening of the adductor muscles was considered important in reducing groin problems by 90.6% of the players in the intervention group. Of the players in the intervention group, 72.5% reported that they spent less than 5 min to complete the programme, 64.7% of players confirmed they would perform the programme the following season, while 52.2% reported they would perform the program less frequently. Of the players in the control group, 53.3% reported that they had performed the program or other exercises to prevent groin injuries during the season.

Practical Takeaways Groin-related injuries are very prevalent in the sport of football, with many players missing time due to them. Players and coaches should consider the addition of an injury-prevention programme as single exercises have been shown to significantly reduce the risk of injury. Therefore, teams should prioritise the importance of strength training and its role in injury prevention. Most players thought that a preventative program with strengthening exercises would reduce the prevalence of groin injuries. The majority of the players reported it took less then 5 min to complete the programme and very few wanted additional exercises. This shows us that players do understand the importance of injury prevention, however, there lies a barrier in implementation.

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Jordan’s Comments “This study shows us that the addition of an injury-prevention program is needed in football and the implementation of the adductor strengthening programme is both time- efficient and effective in reducing groin-related injuries as reported by male football players. It was interesting that although athletes believed there was a high incidence of groin-related injuries in football and that there is a need for preventative training, more than half reported that even though they would perform the programme in the following season, they would perform the programme less frequently and not abide but the current protocol. This relates to my own practice, as I have found that the more in-depth and timeconsuming a programme is, the less likely the athlete is going to adhere to it. We should be choosing specific exercises that offer the most benefit and are the most time-efficient.”

Injury Prevention & Rehab

[Abstract]

Is strength training our best means of reducing injury risk? OBJECTIVE The wide array of conclusions drawn regarding the effectiveness and accessibility of injury prevention programmes can sometimes be overwhelming. Their foci range from strengthening, proprioception, stretching, and multicomponent interventions. This review looked to qualitatively and quantitatively analyse randomised controlled trials (RCT’s) of strength training-based injury prevention programmes, and to present evidence-based recommendations for athletes, coaches, and future research. WHAT THEY DID A very detailed and standardised protocol for the review of select databases (PubMed, Embase, Web of Science, and SPORT-Discus) was carried out for articles published between 2012-2017. Two reviewers evaluated all titles and texts, determined risk of bias, and extracted qualitative data. To determine the strength of the results, the authors performed sub-group analyses of age groups, blinding, intervention type, and outcomes along with a meta-regression on the study quality as a whole. WHAT THEY FOUND Six studies were included in the final analysis, across which a variety of athletes participated, including elite adults, elite youths, amateur males, adolescent females, and military recruits. Increasing weekly volumes of strength training was the main intervention across studies, with one including a multi-modal approach of balance, core stability, and knee alignment. All studies were of high quality and had low risk of bias. The dose-response analysis revealed that increasing volume and intensity of strength training correlated significantly with injury prevention: a 10% increase in repetitions per week was associated with a 13% risk reduction. Overall, strength training programmes reduced sports injuries by an average of 66%.

Practical Takeaways Not only did these strength training programmes significantly reduce sports injuries and more than half the risk of injury, but 4 of the 6 studies reported no adverse effects among their total of 3,991 participants throughout the process (average 8 months of intervention). Based on the results of this study, the authors made several strength training recommendations for coaches and clinicians. They recommend the following: a familiarisation phase with focus on technique before beginning the gradual increase in volume and intensity; working towards training failure thresholds; ensuring good technique and psychological preparedness to prevent acute injuries; ensuring progressive tissue conditioning and training variation to prevent overuse injuries; and include off-season and/ or less demanding periods or phases (see link for infographic below). They also mention that children do not warrant a significantly different approach, but do suggest that supervision, short-term periodisation, long-term variation, individualised %RM loading and appropriate rest periods be included and monitored in this population.

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Steph’s Comments “This review is a breath of fresh air, in my opinion, and for two main reasons. First, it quiets some of the noise surrounding injury prevention programmes and provides solid evidence that we should spend less time worrying about what types of balance and proprioceptive drills we should include and more about how we can effectively implement a progressive, heavy strengthening programme to ensure the athletes have the muscular strength and endurance to readily handle the demands of sport. This is not to say that there is no place in said programme for proprioceptive and neuromuscular training. This is simply to highlight that strengthening should be the overarching focus. Second, it quells some of the hesitancy around heavier loading in athletes in general. I think, especially in physiotherapy and rehab, that we tend to underload patients. This is not always an issue for a return-to-function, but it can absolutely be an issue for a return to highlevel sport. Athletes returning to high-level sport need to be stressed appropriately in order to tolerate the physical and mental requirements of the game, to dominate in those settings and reduce risk of injury all the same.”

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