Abstract
Hamstring strains are a frequent injury in sports and are characterized by a high recurrence rate. The aim of this review was to examine the muscle and tendon architecture in individuals with hamstring injury. A systematic literature search in four databases yielded eleven studies on architecture following injury. Differences in the fascicle length (FL), pennation angle (PA) and muscle size measures (volume, thickness and physiological cross-sectional area) at rest were not significantly different between the previously injured limb and the contralateral limb (p > 0.05). There was moderate evidence that biceps femoris long head (BFlh) FL shortening was greater during contraction in the injured compared to the contralateral limb. The BFlh FL was smaller in athletes with a previous injury compared to uninjured individuals (p = 0.0015) but no differences in the FL and PA of other muscles as well as in the aponeurosis/tendon size were observed (p > 0.05). An examination of the FL of both leg muscles in individuals with a previous hamstring strain may be necessary before and after return to sport. Exercises that promote fascicle lengthening of both injured and uninjured leg muscles may be beneficial for athletes who recover from a hamstring injury.
Highlights
Hamstring injuries are frequent in athletes and may lead to extensive absence from sports [1]
Exercises that promote fascicle lengthening of both injured and uninjured leg muscles may be beneficial for athletes who recover from a hamstring injury
biceps femoris long head (BFlh) injury show no signs of altered size or architecture in their injured limb compared to their non-injured one when they are at rest
Summary
Hamstring injuries are frequent in athletes and may lead to extensive absence from sports [1]. A considerable number of athletes (up to 30%) who recover from such an injury, sustain the same injury again [1,2]. This explains why a history of previous injury is one of the few factors that is associated with an increased risk for injury [3]. When athletes return to play, they may still experience some strength and flexibility deficits [4–8]. Following a controlled rehabilitation program, for example, athletes experience a 9.6% deficit in peak torque relative to the uninjured limb immediately after return to play, which is minimized 6 months later [6]. There are reports that athletes maintain deficits in maximum and explosive strength for an even longer period of time (18–33 months after injury) [9,10]. The question which arises is why these deficits remain after return to play
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