Fig. 4
In vivo gait experiment. a Achilles tendon wave speed, ankle plantarflexion torque, and medical gastrocnemius and tibialis anterior muscle activity over 4 consecutive strides of treadmill walking at 1.5 m s−1. The primary peak in wave speed corresponds to push-off in late stance (stance indicated by shaded regions), when the gastrocnemius is active and ankle torque is high. However, a secondary peak in wave speed is seen in late swing and likely reflects passive tendon stretch due to antagonistic tibialis anterior activity. b Stance phase plots, ensemble averaged over multiple gait cycles for a representative subject show speed-related modulation of both Achilles tendon wave speed and ankle plantarflexion torque
