Sport Injuries and Eccentric-Based Exercises

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Table of Contents

Introduction
Significance of Hamstring Injuries
Research on the Efficacy of Eccentric Based Exercises
Discussion
Conclusion
References

Introduction

Engagement in sporting activities is a defining characteristic of human life. Through sports, people are able to keep fit, achieve personal fulfilment, and provide entertainment for others. Most sports require the participants to engage in some physically demanding activities. This puts a strain on the muscles of the individual and it can result in injury. In sports that require high-speed running, acute hamstring injuries are common. Injuries are undesirable since they prevent the individual from engaging in the sport or reduce his/her performance. This paper will set out to discuss, with reference to the most recent peer-reviewed literature, the evidence for the efficacy of eccentric based exercise programs for the prevention of recurrent hamstring injuries. It will begin by explaining why hamstring injuries deserve special attention when addressing the issues of sporting injuries.

Significance of Hamstring Injuries

Among the various sporting injuries that athletes face, hamstring strain injuries are among the most common. Opar, Morgan and Shield (2012) note that these injuries are common in a number of sports and their occurrence rates have increased in recent times. The effects of hamstring injuries range from limited loss of function in the event of microscopic tearings to the complete loss of function when a full rupture of the muscle has occurred. In either case, these injuries have significant negative impacts on the athlete. To begin with, they result in a considerable lose of time from training and competition as the individual recovers from the injury. Opar et al. (2012) document that athletes suffer from financial losses as they miss competitions or demonstrate diminished athletic performances in their sports.

A troubling reality with hamstring injuries is that they have a high rate of recurrence. Clark (2011) asserts that recurrent hamstring injuries are especially dangerous since they can cause severe hamstring problems and even prevent the athlete from ever regaining his/her pre-injury level of performance. Previous hamstring injury is consistently associated with new hamstring injuries. Research by Opar et al (2012) on injuries among professionals in the Australian Football League revealed that 27% of all hamstring injuries were recurrences of previous injuries. Considering the significant negative consequences that hamstring injuries have on an athlete, it would be important to identify effective ways of preventing these recurrences. One intervention strategy that promises to address recurrent hamstring muscle injury is eccentric based exercise programs. A number of studies support this strategy for the management of recurrent hamstring injuries.

Research on the Efficacy of Eccentric Based Exercises

Eccentric exercises help the damaged muscles achieve full recovery therefore reducing the predisposition to re-injury. A study by Brukner, Nealon, Morgan, Burgess and Dunn (2014) reveals that following a hamstring injury, the affected muscles recover naturally. However, the muscles are not able to return to their pre-injury strength levels naturally. Imaging studies of human muscle tissue show that there is incomplete healing following muscle strains. This explains why athletes with previous injuries have a higher predisposition to re-injury compared with their counterparts who have never had hamstring injuries. Interventions aimed at remodelling the healed muscle tissue can reduce the risk associated with having had previous injuries. In the first few weeks following a hamstring injury, the muscles of the individual undergo regeneration (Brukner et al. 2014). Eccentric based exercise programs have been shown to result in muscle-tendon junction remodelling. Hamstring muscle injuries are often associated with reduced eccentric hamstring strength. Through eccentric exercise, the strength deficits in the hamstrings are normalised after some time. Brukner et al. (2014) assert that exercise regimes that result in the increase of the muscle strength are therefore likely to prevent reoccurrence of the injuries. These exercises also cause intramuscular collagen remodelling which restores the muscles almost to their pre-injury form.

Knee-flexion strength increase contributes to hamstring injury prevention among athletes. Exercises that increase this strength can therefore have a positive impact in re-injury prevention. A study by Orishimo and McHugh (2014) set out to establish the effect of eccentric biased exercise program on the knee flexion strength. The angle of peak knee flexion torque has a direct implication on hamstring injuries among athletes. Research indicates that individuals who produce knee flexor torque at shorter muscle lengths are at greater risks of incurring hamstring injuries (Orishimo & McKugh 2014). It can therefore be surmised that exercises that lead to peak knew flexor torque at higher muscle lengths could significantly reduce the risk of hamstring injury. The study by Orishimo and McHugh (2014) demonstrated that eccentrically biased exercises led a knee flexor strength improvement of 9% and a maximum knee extension angle increase of 6 degrees. These improvements have the positional to contribute in re-injury prevention since they lead in improved strength and flexibility in the athlete.

Eccentric exercise programs facilitate positive changes in muscle property creating more resilience against injury. Brukner et al. (2014) engage in a study aimed at examining the efficacy of various strategies for the management of recurrent hamstring injuries. They begin by noting that eccentric exercise result in changes in muscle properties. This is important when dealing with athletes who have experienced previous injuries. When a person suffers from a hamstring injury, he/she experiences altered muscle properties. These contribute to the increase in risk of re-injury. Brukner et al. (2014) observe that the eccentric exercise program changes the muscle properties to pre-injury status. This assertion is corroborated by Thorborg (2012) who declares that eccentric exercise programs have a huge hamstring re-conditioning capability. When the athlete receives early exposure to eccentric strengthening as part of a hamstring rehabilitation program, a remarkable increase in hamstring strength is observed. According to Brukner et al. (2014), the exercises help address the eccentric strength deficits caused by the previous hamstring injury therefore decreasing the risk of re-injury.

Eccentrically biased programmes are beneficial in terms of overall strength gains. A study by Krist, van Beijsterveldt, Backx and de Wit (2013) showed that injury prevention programs that included eccentric hamstring exercise reduced the costs associated with soccer injuries. In this injury prevention programs, sufficient training loads were used in the eccentric hamstring exercise. A key factor of the eccentric based exercise programs is that they are formulated to increase strength at the extremes of the functional range of motion (Krist et al. 2014). This has a direct impact on hamstring injury since weakness at long muscle lengths may have implications for injury risk and injury recurrence. Some eccentric based exercise programs are structured to address the functional range of motion through which a muscle group operates. Research indicates that eccentric strength training near the end of the functional range of motions for a given muscle group increases the ability of the muscles to absorb lengthening forces. Through the controlled muscle strain exercises, the energy required to strain a muscle to failure is increased. The athlete’s muscles are therefore able to resist lengthening, which is beneficial to avoiding strain injury.

Through eccentric biased programs, the mechanical limits of the athletes muscles are increased therefore reducing the disposition to hamstring re-injuries. Following a hamstring injury, the muscles affected exhibit a reduction in the mechanical limit beyond which injury occurs. Exercises aimed at increasing this limit can reduce the risk of re-injury. Petersen, Thorborg, Nielsen, Budtz-Jorgensen and Holmich (2011) carried out an expanded randomised controlled trial to investigate the preventive effect of eccentric strengthening of the hamstring muscles in a group of 942 football players. This study demonstrated that eccentric exercise programs resulted in a significant decrease in the rate of recurrent acute hamstring injuries. These positive results occur since eccentric training leads to an increase in the mechanical limits of the muscles. This is an important factor since hamstring injuries occur when the athlete engages in a traumatic event that exceeds the mechanical limits of the muscle. According to Petersen et al. (2011), eccentric exercise programs lead to the altering of the mechanical properties of the hamstrings. This muscle strengthening makes it possible for athletes to regain or exceed their pre-injury mechanical limits.

Studies on specific eccentric exercise programs show that these exercises result in significant reductions in injury recurrence. Thorborg (2012) assesses the effects of the Nordic hamstring exercise program on re-injuries. The Nordic hamstring exercise is a bodyweight exercise performed by the athlete to increase eccentric hamstring torque and shift the torque joint angle curve of the hamstrings to longer muscle lengths. Thorborg (2012) analysed the results of a large-scaled randomised controlled trial on the efficacy of this exercise program to see what effect it had in reducing the re-injury rates among soccer players. The study indicated that intervening with this form of exercise over a 10-weeek period led to a reduction of hamstring injuries by 70%. This reduction considered new injuries and re-injuries among the athletes. When considering the re-injuries alone, the study found that by intervening with the Nordic hamstring exercise, re-injuries were reduced by 85%.

Discussion

Injury prevention is the ultimate goal of the sports medicine professional. However, due to the unpredictable nature of sporting events, it might be impossible to prevent all injuries. A worthwhile goal would therefore be to implement strategies that reduce injuries or re-occurrence of injuries. From the discussions provided herein, it is clear that eccentric based exercise has huge potential in reducing hamstring injuries. However, In spite of the evidence for the efficacy of eccentric based exercise programs in preventing hamstring re-injury, there is still limited understanding on the exact biomechanics of the intervention. Thorborg (2012) admits that the precise preventive injury mechanism that is promoted through eccentric strength training is not yet clearly understood. This lack of a theoretical framework has caused some sports medicine professionals to criticise these programs. However, multiple studies have shown that these exercises are effective in preventing recurrent hamstring injuries (Thorborg 2012; Brukner et al. 2014). It would therefore be negligent of the sporting community if it failed to take advantage of this effective intervention method. Brukner et al. (2014) declares that eccentric training needs to be made the foundation of muscle injury rehabilitation.

Conclusion

There is agreement that recurrent hamstring injuries pose major problems to athletes in most sports. To tackle this issue, researchers have over the decades attempted to come up with the most efficient method to prevent hamstring injury recurrence. This paper set out to discuss the efficacy of one of this proposed solutions, which is eccentric based exercise programs. By referencing the most recent literature on the topic of recurrent hamstring injuries prevention, the paper has discussed the efficacy of eccentric based programs. The evidence provided in this paper shows that eccentric based exercise programs are effective in prevention the recurrence of hamstring injuries in athletes. Due to the proven positive preventive effects of these exercises, they should be implemented by even more sporting health professionals to benefit athletes with past hamstring injuries.

References

Brukner, P Nealon, A Morgan, C Burgess, D & Dunn, A 2014, ‘Recurrent hamstring muscle injury: applying the limited evidence in the professional football setting with a seven-point programme’, Br J Sports Med, vol.48, no.3, pp. 929–938

Clark, RA 2011, ‘Hamstring Injuries: Risk Assessment and Injury Prevention’, Ann Acad Med Singapore, vol.37, no.3, pp. 341-346.

Krist, M van Beijsterveldt, MA Backx, JF & de Wit, A 2013, ‘Preventive exercises reduced injury-related costs among adult male amateur soccer players: a cluster-randomised trial’, Journal of Physiotherapy, vol.59, no.1, pp.15-23.

Opar, DA Morgan, DM Shield, AJ 2012, ‘Hamstring Strain Injuries Factors that Lead to Injury and Re-Injury’, Sports Med, vol.42, no.3, pp. 209-226.

Orishimo, KF & McHugh, PM 2014, ‘Effect of an Eccentrically-biased Hamstring Strengthening Home Program on Knee Flexor Strength And The Length-tension Relationship’, J Strength Cond Res, vol.23, no.2, pp. 1-5.

Petersen, J Thorborg, K Nielsen, MB Budtz-Jorgensen, E & Holmich P 2011, ‘Preventive effect of eccentric training on acute hamstring injuries in men’s soccer: a cluster-randomized controlled trial’, Am J Sports Med, vol. 39 no.2, pp. 2296-2303.

Thorborg, K 2012, ‘Why hamstring eccentrics are hamstring essentials’, Br J Sports Med, vol.46, no.2, pp. 463–465.

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