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

Biomechanical characteristics of an anterior cruciate ligament injury in javelin throwing

Purpose： The purpose of this study was to understand the mechanism of an anterior cruciate ligament （ACL） injury in javelin throwing and javelin throwing techniques relevant to this ACL injury. Methods： The patient in this study was an elite female javelin thrower who completed the first three trials and sustained a non-contact ACL injury on her left knee in the fourth trial of javelin throwing during a recent track and field meet. Three-dimensional kinematic data were collected in the injury and non-injury trials. The kinematic data of 52 male and 54 female elite javelin throwers were obtained from a javelin throwing biomechanical database. Results： The patient had greater forward center of mass velocity and less vertical center of mass velocity after the first 25% of the delivery phase in the injury trial compared to non-injury trials. The patient had less left knee flexion angle and angular velocity but similar left knee valgus and internal rotation angles during the first 21% of the delivery phase in the injury trial compared to non-injury trials. The video images showed an obvious tibia anterior translation at the 30% of the delivery phase in the injury trial. The left knee flexion angle and angular velocity at the time of the left foot landing and the maximal left knee flexion angle during the delivery phase were not significantly correlated to the official distance for 52 male and 54 female elite javelin throwers. Conclusion： The ACL injury in this study occurred during the first 30% of the delivery phase, most likely during the first 25% of the delivery phase. A stiff landing of the left leg with a small knee flexion angle was the primary contributor to this injury. Javelin throwers may have a soft left leg landing with a flexed knee, which may help them prevent ACL injuries without compromising performance.

Anterior cruciate ligament injuries in soccer:Loading mechanisms,risk factors,and prevention programs

Anterior cruciate ligament （ACL） injuries are common in soccer. Understanding ACL loading mechanisms and risk factors for ACL injury is critical for designing effective prevention programs. The purpose of this review is to summarize the relevant literature on ACL loading mechanisms, ACL injury risk factors, and current ACL injury prevention programs for soccer players. Literature has shown that tibial anterior translation due to shear force at the proximal end of tibia is the primary ACL loading mechanism. No evidence has been found showing that knee valgus moment is the primary ACL loading mechanism. ACL loading mechanisms are largely ignored in previous studies on risk factors for ACL injury. Identified risk factors have little connections to ACL loading mechanisms. The results of studies on ACL injury prevention programs for soccer players are inconsistent. Current ACL injury prevention programs for soccer players are clinically ineffective due to low compliance. Future studies are urgently needed to identify risk factors for ACL injury in soccer that are connected to ACL loading mechanisms and have cause-and-effect relationships with injury rate, and to develop new prevention programs to improve compliance.

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