Regional muscle activation of the Biceps femoris

The purpose of this study was to examine regional BFlh activation during isometric knee flexion. Using an isokinetic device and high-density EMG, 11 males performed contractions at all combinations of short, medium and long MTU lengths and three torque levels (30%MVC, 60%MVC, 90%MVC). Distal BFlh exhibited significantly higher activation at 60% MVC and 90%MVC than proximal, indicating intensity-dependent heterogeneity. No effects of muscle length on muscle activation were found. Additionally, the findings suggest BFlh operates on the ascending limb of the force-length relationship. Practitioners should be mindful of potential intramuscular variations in biarticular muscles during different contraction circumstances with potential implications for hamstring injury risk assessment and exercise selection.