Purpose: To investigate the effects of anterior cruciate ligament injury on mechanical and contractile characteristics of the skeletal muscles of the lower extremity in competitive soccer players through tensiomyography (TMG).
Methods: All competitive male soccer players with confirmed acute anterior cruciate ligament tear included underwent resting TMG assessment of muscles of both lower extremities before anterior cruciate ligament reconstruction. The same values were obtained from a sex- and sports level-matched control group. The maximal displacement, delay time, contraction time, sustained time, and half-relaxation time were obtained for the following muscles in all subjects: vastus medialis, vastus laterals, rectus femoris, semitendinosus, biceps femoris, gastrocnemius medialis, and gastrocnemius lateralis.
Results: The majority of TMG parameters were higher in the injured compared to the control group. The contraction time of the vastus medialis, vastus lateralis, and rectus femoris was significantly higher in the injured compared to the control group (p = 0.003, p = 0.001, and p < 0.001, respectively). The biceps femoris was the only hamstring muscle with significant differences between groups, with increased contraction time and maximal displacement in the injured compared to the control group (p = 0.002 and p < 0.001, respectively). The gastrocnemius medialis was clearly more affected than the gastrocnemius lateralis, with contraction time, half-relaxation time, and maximal displacement significantly higher (p = 0.01, p = 0.03, and p < 0.001, respectively), and the sustained time significantly lower (p = 0.01), in the injured compared to the control group. The contraction time of the vastus medialis, vastus lateralis, rectus femoris, semitendinosus, and biceps femoris was significantly higher in the injured compared to non-injured side in the anterior cruciate ligament-injured group (p = 0.007, p = 0.04, p = 0.004, p = 0.02, and p = 0.02, respectively).
Conclusions: Anterior cruciate ligament injury caused a decrease in contraction velocity (in quadriceps, hamstrings and gastrocnemius medialis), resistance to fatigue (in quadriceps and gastrocnemius medialis), and muscle tone/stiffness (in hamstrings and gastrocnemius medialis). Overall, it was demonstrated that these effects were worst in the quadriceps and gastrocnemius medialis compared to the hamstring and gastrocnemius lateralis. These findings may contribute to a better design of rehabilitation programs in order to optimize the recovery and potentially increase sport performance at return to sport.
Level of evidence: Prognostic study, Level II.
Keywords: ACL reconstruction; Neuromuscular; Soccer players; Tensiomyography.