Mechanical interactions between the biceps femoris long and short heads: Implications for T-junction hamstring...

Although force transfer during elongation occurs longitudinally and transversely, the influence of transverse force transfer between the biceps femoris long head and short head remains unclear. This study aimed to investigate whether separating the intermuscular connections between the biceps femoris long head and short head alters tension in the biceps femoris long head. Eight human cadaver legs were used, and ultrasonic shear wave elastography measurements were performed under four conditions: (1) intact, (2) removal of all tissues from the skin to the deep fascia, (3) intermuscular dissection, and (4) biceps femoris short head detachment. Measurements were taken in four limb positions, defined by hip and knee joint angles, under each tissue condition. The shear modulus of the biceps femoris long head significantly increased by 62.2% after intermuscular dissection compared to fascia removal, and further increased by 174.7% after biceps femoris short head detachment. In contrast, the shear modulus of the biceps femoris short head significantly decreased by 36.0% following intermuscular dissection and by 75.1% after detachment. In conclusion, reducing biceps femoris short head tension while increasing biceps femoris long head tension may influence muscle stress distribution, particularly during movement.