Mechanics of The Medial Gastrocnemius–Tendon Unit in Behaving more Efficiently in Habitual Non-Rearfoot Strikers than in Rearfoot Strikers during Running

This study aims to quantify how habitual foot strike patterns would affect ankle kinetics and the behavior mechanics of medial gastrocnemius–tendon unit (MTU) during running. A total 14 runners with non-rearfoot (NRFS) 15 rearfoot (RFS) ran on an instrumented treadmill at a speed 9 km/h. An ultrasound system motion capture were synchronously triggered collect images gastrocnemius (MG) marker positions along ground reaction forces (GRF) Ankle (moment power) MG/MTU mechanical properties (MG shortening length, velocity, force, power, MTU shortening/lengthening calculated. Independent t-tests performed compare two groups runners. Pearson correlation was conducted detect relationship between angle mechanics. Compared RFS runners, NRFS had 1) lower angles greater peak moments; 2) shortening/change length contraction velocity MG force; 3) lengthening, lengthening power; 4) positively related change fascicle stance phase. The negatively force power. in appears contract relatively isometric slower velocity. Moreover, MTU, leading stronger stretch reflex response potentially.