Is Muscle Architecture Different in Athletes with a Previous Hamstring Strain? A Systematic Review and Meta-Analysis

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.

A retrospective comparison of the biceps femoris long head muscle structure in athletes with and without hamstring strain injury history

“…A recent meta-analytic study [26] indicated moderately shorter BFlh fascicle lengths of injured legs of the athletes (effect size = 0.57), which is similar to our present research (effect size = 0.62). Variability of results in the literature might have multifactorial causes including athlete age [47, 78,79], ethnicity [80], sports disciplines [81], rehabilitation process [82][83][84], abd ultrasound measurement methods [17,38].…”

“…A previous study [ 26 ] suggested that neural inhibition following the injury [ 24 – 29 ] and reduced exertion may cause BFlh fascicle shortening at the early phase of rehabilitation [ 22 ]. Together with the former, decreased participation in sports [ 24 ] are a possible underlying mechanism for the shortening of BFlh fascicle lengths after injury.…”

“…Future studies are needed to monitor the architecture of the hamstrings before the HSI, during rehabilitation, and after returning to play for a better understanding of the mechanisms behind the architectural alterations after the HSI. Based on the findings of this study, it may be suggested that rehabilitation programs should include exercises that can lead to fascicle lengthening in the hamstrings of both legs of previously injured athletes to minimise the possibility of microscopic damage of the fascicles during eccentric contraction [ 25 , 26 , 85 ].…”

“…However, due to the nature of the retrospective study, longitudinal trials are needed to understand the differences in athletes after HSI. A previous study [26] suggested that neural inhibition following the injury [24][25][26][27][28][29] and reduced exertion may cause BFlh fascicle shortening at the early phase of rehabilitation [22]. Together with the former, decreased participation in sports [24] are a possible underlying mechanism for the shortening of BFlh fascicle lengths after injury.…”

“…Therefore, this study aimed to compare the BFlh fascicle length via the EFOV technique, passive stiffness of the mid-belly and MTJ of the BFlh via ultrasound-based shear wave elastography between previously injured legs and uninjured contralateral legs of athletes with HSI history, and both legs of athletes without HSI history. The hypotheses of this study were considered as follows: 1) previously injured legs will have shorter fascicles in the BFlh compared to contralateral uninjured legs and both legs of the athletes without HSI due to possible decreased exertion at the beginning of rehabilitation [22], reduced involvement in sports [24], and/or neural inhibition after the HSI [24][25][26][27][28][29]; 2) previously injured legs will have higher stiffness in the BFlh after the injury compared with contralateral uninjured legs and both legs of the athletes without HSI due to possible contractures or scars in the muscle [24,26,[30][31][32][33][34][35].…”