Injury rate,mechanism,and risk factors of hamstring strain injuries in sports:A review of the literature

Hamstring strains are one of most common sports injuries.The purpose of this literature review is to summarize studies on hamstring strain injury rate,mechanism,and risk factors in the last several decades with a focus on the prevention and rehabilitation of this injury.Hamstring injury commonly occurs in sporting events in which high speed sprinting and kicking are frequently performed,such as Australian football. English rugby,American football,and soccer.Basic science studies have demonstrated that a muscle strain injury occurs due to excessive strain in eccentric contraction instead of force,and that elongation speed and duration of activation before eccentric contraction affect the severity of the injury.Hamstring strain injury is likely to occur during the late swing phase and late stance phase of sprint running.Shortened optimum muscle length,lack of muscle flexibility,strength imbalance,insufficient warm-up,fatigue,lower back injury,poor lumbar posture,and increased muscle neural tension have been identified as modifiable risk factors while muscle compositions,age,race,and previous injuries are non-modifiable risk factors.The theoretical basis of some of these risk factors,however,is lacking,and the results of clinical studies on these risk factors are inconsistent.Future studies are needed to establish the cause-and-effect relationships between those proposed risk factors and the injury.

Effects of flexibility and strength training on peak hamstring musculotendinous strains during sprinting

Background:Hamstring injury is one of the most common injuries in sports involving sprinting.Hamstring flexibility and strength are often considered to be modifiable risk factors in hamstring injury.Understanding the effects of hamstring flexibility or strength training on the biomechanics of the hamstring muscles during sprinting could assist in improving prevention strategies and rehabilitation related to these injuries.The purpose of this study was to determine the effects of altering hamstring flexibility or strength on peak hamstring musculotendinous strain during sprinting.Methods:A total of 20 male college students(aged 18-24 years)participated and were randomly assigned to either a flexibility intervention group or a strength intervention group.Each participant executed exercise training 3 times a week for 8 weeks.Flexibility,sprinting,and isokinetic strength testing were performed before and after the 2 interventions.Paired t tests were performed to determine hamstring flexibility or strength intervention effects on optimal hamstring musculotendinous lengths and peak hamstring musculotendinous strains during sprinting.Results:Participants in the flexibility intervention group significantly increased the optimal musculotendinous lengths of the semimembranosus and biceps long head(p<0.026)and decreased peak musculotendinous strains in all 3 bi-articulate hamstring muscles(p<0.004).Participants in the strength-intervention group significantly increased the optimal musculotendinous lengths of all 3 hamstring muscles(p<0.041)and significantly decreased their peak musculotendinous strain during sprinting(p<0.017).Conclusion:Increasing hamstring flexibility or strength through exercise training may assist in reducing the risk of hamstring injury during sprinting for recreational male athletes.

The effect of hamstring flexibility on peak hamstring muscle strain in sprinting

Background:The effect of hamstring flexibility on the peak hamstring muscle strains in sprinting,until now,remained unknown,which limited our understanding of risk factors of hamstring muscle strain injury(hamstring injury).As a continuation of our previous study,this study was aimed to examine the relationship between hamstring flexibility and peak hamstring muscle strains in sprinting.Methods:Ten male and 10 female college students participated in this study.Hamstring flexibility,isokinetic strength data,three-dimensional(3D)kinematic data in a hamstring isokinetic test,and kinematic data in a sprinting test were collected for each participant.The optimal hamstring muscle lengths and peak hamstring muscle strains in sprinting were determined for each participant.Results:The muscle strain of each of the 3 biarticulated hamstring muscles reached a peak during the late swing phase.Peak hamstring muscle strains were negatively correlated to hamstring flexibility(0.1179 ≤ R2≤ 0.4519,p = 0.001) but not to hip and knee joint positions at the time of peak hamstring muscle strains.Peak hamstring muscle strains were not different for different genders.Peak muscle strains of biceps long head(0.071 ± 0.059) and semitendinosus(0.070 ± 0.055) were significantly greater than that of semimembranosus(0.064 ± 0.054).Conclusion:A potential for hamstring injury exists during the late swing phase of sprinting.Peak hamstring muscle strains in sprinting are negatively correlated to hamstring flexibility across individuals.The magnitude of peak muscle strains is different among hamstring muscles in sprinting,which may explain the different injury rate among hamstring muscles.

Research in prevention and rehabilitation of hamstring muscle strain injury

Hamstring muscle strain injury is the most common and prevalent injury in sports involving high-speed running,such as American football,Australian football,English rugby,soccer,track and field,and cricket.1Hamstring muscle strain injury also has a high recurrence rate of up to 48%.2The average practice and game time loss due to hamstring injury is between17 and 60 days,contingent on the grade of injury.2Severe hamstring muscle strain injuries,and associated recurrent inju-