Fig. 1

Schematic diagram of the muscle-tendon-unit (MTU) geometry model and contraction dynamic model of the plantarflexor muscles during treadmill walking tasks. a A human participant walking on a treadmill. b The MTU geometry model, where the ankle joint rotation center in the sagittal plane is denoted as O, and the proximal and distal osteotendinous junction points near the knee joint and heel are denoted as A and B. SOL and LGS muscles are referred as \(i=1,2\). c The MTU contraction dynamic model, where the anatomical structure and contraction force generation of the MTU are illustrated