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.

Mechanism of hamstring muscle strain injury in sprinting

Hamstring muscle strain injury is one of the most common injuries in sports involving sprinting and kicking.Hamstring muscle strain injuries occur at a high rate and have a high re-injury rate,which results in loss of training and competition time,which has a significant impact on the quality of life of the injured athletes.~1Preventing and rehabilitating hamstring muscle strain injury is an important task for clinicians and scientists in sports medicine.Understanding the mechanisms underlying hamstring injury is critical for developing appropriate strategies to prevent and rehabilitate hamstring injuries.Understanding the

Relationships among hamstring muscle optimal length and hamstring flexibility and strength

Background:Hamstring muscle strain injury(hamstring injury) due to excessive muscle strain is one of the most common injuries in sports.The relationships among hamstring muscle optimal lengths and hamstring flexibility and strength were unknown,which limited our understanding of risk factors for hamstring injury.This study was aimed at examining the relationships among hamstring muscle optimal length and flexibility and strength.Methods:Hamstring flexibility and isokinetic strength data and three-dimensional kinematic data for hamstring isokinetic tests were collected for11 male and 10 female recreational athletes.The maximal hamstring muscle forces,optimal lengths,and muscle lengths in standing were determined for each participant.Results:Hamstring muscle optimal lengths were significantly correlated to hamstring flexibility score and gender,but not to hamstring strength.The greater the flexibility score,the longer the hamstring muscle optimal length.With the same flexibility score,females tend to have shorter hamstring optimal muscle lengths compared to males.Hamstring flexibility score and hamstring strength were not correlated.Hamstring muscle optimal lengths were longer than but not significantly correlated to corresponding hamstring muscle lengths in standing.Conclusion:Hamstring flexibility may affect hamstring muscle maximum strain in movements.With similar hamstring flexibility,hamstring muscle maximal strain in a given movement may be different between genders.Hamstring muscle lengths in standing should not be used as an approximation of their optimal lengths in calculation of hamstring muscle strain in musculoskeletal system modeling.

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.

非接触式前交叉韧带损伤的生物力学风险因素：一项随机的生物力学模型研究(英文)

Background:Significant efforts have been made to identify modifiable risk factors of non-contact anterior cruciate ligament(ACL) injuries in male and female athletes.However,current literature on the risk factors for ACL injury are purely descriptive.An understanding of biomechanical relationship between risk and risk factors of the non-contact ACL injury is necessary to develop effective prevention programs. Purpose:To compare lower extremity kinematics and kinetics between trials with and without non-contact ACL injuries and to determine if any difference exists between male and female trials with non-contact ACL injuries regarding the lower extremity motion patterns. Methods:In this computer simulation study,a stochastic biomechanical model was used to estimate the ACL loading at the time of peak posterior ground reaction force(GRF) during landing of the stop-jump task.Monte Carlo simulations were performed to simulate the ACL injuries with repeated random samples of independent variables.The distributions of independent variables were determined from in vivo laboratory data of 40 male and 40 female recreational athletes. Results:In the simulated injured trials,both male and female athletes had significantly smaller knee flexion angles,greater normalized peak posterior and vertical GRF.greater knee valgus moment,greater patella tendon force,greater quadriceps force,greater knee extension moment. and greater proximal tibia anterior shear force in comparison to the simulated uninjured trials.No significant difference was found between genders in any of the selected biomechanical variables in the trials with simulated non-contact ACL injuries. Conclusion:Small knee flexion angle,large posterior GRF.and large knee valgus moment are risk factors of non-contact ACL injury determined by a stochastic biomechanical model with a cause-and-effect relationship.

足球运动中前十字韧带损伤:负载机制、风险因素及预防方案（英文）

足球运动中前十字韧带(ACL)损伤非常常见。了解ACL的负载机制以及造成ACL损伤的危险因素有助于设计有效的预防方案。本综述目的在于为足球运动员总结关于ACL负载机制、ACL损伤因素,以及当前关于ACL损伤预防方案的研究。文献表明,近端胫骨的剪切力引起的胫骨前移是最主要的ACL负载机制,并无证据表明膝外翻是ACL的主要负载机制。之前有关ACL损伤危险因素的研究大都忽视ACL负载机制,已确定的风险因素几乎都与ACL负载机制无关。关于球员ACL损伤预防方案的研究结果互不一致。现有的足球运动员ACL损伤预防方案依从性低、临床效果不佳。未来的研究迫切需要确定与球员ACL负载机制相关的、与ACL损伤有因果关系的危险因素,开发新的预防方案以提高临床依从性。

The effect of performance demands on lower extremity biomechanics during landing and cutting tasks

Background: Anterior cruciate ligament(ACL) injuries commonly occur during the early phase of landing and cutting tasks that involve sudden decelerations. The purpose of this study was to investigate the effects of jump height and jump speed on lower extremity biomechanics during a stop-jump task and the effect of cutting speed on lower extremity biomechanics during a side-cutting task.Methods: Thirty-six recreational athletes performed a stop-jump task under 3 conditions: jumping fast, jumping for maximum height, and jumping for 60% of maximum height. Participants also performed a side-cutting task under 2 conditions: cutting at maximum speed and cutting at 60% of maximum speed. Three-dimensional kinematic and kinetic data were collected.Results:The jumping fast condition resulted in increased peak posterior ground reaction force(PPGRF), knee extension moment at PPGRF,and knee joint stiffness and decreased knee flexion angle compared with the jumping for maximum height condition. The jumping for 60% of maximum height condition resulted in decreased knee flexion angle compared with the jumping for maxrimum height condition. Participants demonstrated greater PPGRF, knee extension moment at PPGRF, knee valgus angle and varus moment at PPGRF, knee joint stiffness, and knee flexion angle during the cutting at maximum speed condition compared with the cutting at 60% maximum speed condition.Conclusion: Performing jump landing at an increased jump speed resulted in lower extremity movement patterns that have been previously associated with an increase in ACL loading. Cutting speed also affected lower extremity biomechanics. Jump speed and cutting speed need to be considered when designing AC.L injury risk screening and injury prevention programs.

Comment on “The late swing and early stance of sprinting are most hazardous for hamstring injuries” by Liu et al.

We have carefully read the description of the proposed mechanisms of hamstring muscle strain injury by Liu et al.1and noticed that they suggest that hamstring strain injuries may be associated with extensive muscle force and occur during the early stance phase of sprinting when the hamstrings are thought to work concentrically.We did not find any evidence in our extensive literature review to support this