Bilateral differences in hamstring coordination in previously injured elite athletes.

Area of Science:

• Sports Medicine
• Biomechanics
• Muscle Physiology

Background:

• Hamstring strain injuries (HSIs) can lead to lasting changes in muscle coordination.
• Understanding these changes post-rehabilitation is crucial for athlete recovery and injury prevention.
• Previous HSIs may affect hamstring muscle coordination bilaterally, even without current symptoms.

Purpose of the Study:

• To investigate bilateral differences in hamstring muscle coordination in elite athletes following a unilateral HSI.
• To assess if these coordination differences persist after rehabilitation and return to sport.

Main Methods:

• Seventeen elite athletes with a history of unilateral biceps femoris (BF) injury participated.
• Surface electromyography (sEMG) measured hamstring muscle activity (BF, semimembranosus (SM), semitendinosus).
• Isometric knee flexion tasks at 20% and 50% maximal voluntary contraction were performed to assess muscle torque contribution using sEMG, physiological cross-sectional area (PCSA), and moment arm.

Main Results:

• The injured BF muscle contributed less to knee flexion torque in the injured limb compared to the uninjured limb (-5.6%).
• This deficit was compensated by an increased contribution from the semimembranosus (SM) muscle in the injured limb (+5.6%).
• Reduced PCSA in the injured BF and increased activation in the synergist SM muscle explained these force-sharing changes.

Conclusions:

• Bilateral coordination differences exist in elite athletes with a history of HSI, persisting post-rehabilitation.
• Altered hamstring muscle force-sharing, with reduced BF contribution and increased SM activation, is evident.
• Further research is needed to determine if these coordination deficits are a risk factor for recurrent hamstring injuries.