INTRODUCTION: Hamstring strain injury (HSI) is recognized to impair isometric strength and range of motion (ROM) during a passive straight leg raise (SLR)(1). While such deficits have been reported in various sports, little is known regarding injury-induced impairments in elite athletes. Moreover, SLR amplitude is a global measurement and does not provide information about the localized adaptations close to the injury locations. Therefore, the aim of this study is to determine the effect of HSI history on strength, flexibility and local muscle elasticity in high elite athletes. METHODS: Among the fifty-one elite athletes (participating in the Olympic, World and European competitions in athletics, rugby seven and bobsleigh) that completed a survey on their injury history, fourteen participants (age: 25.0±5.3 years, height: 178.5±10.7 cm, weight: 79.7±17.8kg) reported HSI on one side, more than 30 days prior to the testing. Maximal ROM during a SLR test, maximal knee flexor force during Nordic hamstring exercise (NHE), peak torque during 60°.s-1 isokinetic eccentric knee flexion (ECC), peak torque during isometric contraction (MVC) were evaluated for knee flexors and hip extensors. Muscle elasticity was assessed using shear-wave elastography on the biceps femoris (BF), semitendinosus (ST) and semimembranosus (SM). RESULTS: No significant differences were observed between previous HSI side and non-injured (NI) side in any of the variables. The mean and standard deviation for HSI side and NI side were respectively 7.8±1.9 vs 8.0±1.1 N.kg-1 (674±235 vs 637±188N) for NHE (p=0.83), 2.3±0.5 vs 2.3±0.7 N.m.kg-1 (123±87 vs 144±92 N.m) for the ECC torque of knee flexors (p=0.35), 1.7±0.5 vs 1.9±0.7 N.m.kg-1 (172±69 vs 184±72 N.m) for the MVC of hip extensors (p=0.37), 2.2±0.6 vs. 2.4±0.5 N.m.kg-1 (132±59 vs 148±78 N.m) for the MVC of knee flexors (p=0.94). ROM on SLR was 93±11 vs 91±10° for HSI side and NI side respectively. For muscle elasticity, for HSI side and NI side results were respectively, 17.4±6.0 vs 18.2±6.9 for BF (p=0.66), 19.6±5.2 vs 18.9±5.1 for SM (p=0.61) and 17.7±6.2 vs 15.3±4.6 KPa for ST (p=0.07). CONCLUSION: Descriptive data of this study provides reference values for elite athletes from sprint-based sports. HSI history does not seem to be associated with deficit in strength or flexibility in elite athletes. These findings differ from some previous studies and may reflect the positive adaptations to thorough rehabilitation implemented for athletes involved in Olympic quest. The lack of difference in bilateral muscle elasticity infirm the hypothesis that post-injury collagen inclusion in injured muscle would increase muscle stiffness.
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