Shear Stress Applied to the Myotendinous Junction of the Biceps Femoris Long Head and Semimembranosus during the Late Swing Phase of High-speed Running

Abstract

The purposes of this study were 1) to clarify the difference in shear stress applied to the proximal myotendinous junction and musculotendon dynamics between the biceps femoris long head (BFlh) and semimembranosus (SM) during the late swing phase of high-speed running, and 2) to assess the effects of musculotendon parameters such as insertion points, tendon slack length, optimal muscle fiber length, pennation angle at optimal muscle fiber length, and maximal isometric force in the hamstring muscles on muscle force and shear stress of the BFlh and SM. Ten soccer players performed running trials at maximum effort. A three-dimensional musculoskeletal model with 43 Hill-type musculotendon actuators of the right leg was used to compute the musculotendon dynamics during the late swing phase of high-speed running. While peak muscle force of the BFlh was significantly smaller than that of the SM, the BFlh had significantly higher peak shear stress and musculotendon elongation velocity at peak shear stress than the SM. The results indicate that the BFlh has a higher risk of injury at the proximal myotendinous junction during the late swing phase of high-speed running. Additionally, shorter tendon slack length in the BFlh and SM most affected the increase of muscle force and shear stress.