Figure 4.

Mechanical work developed by gastrocnemius (GAS) and soleus (SOL) fiber and tendon as a function of peak tendon strain at maximal isometric force (ε₀). (a) Fiber positive and (b) negative work during stretching. (c) Fiber positive work during shortening. (d) Negative work stored in the tendon during stretching due to sources other than muscle fibers, given as percentage of the muscle-tendon unit (MTU) work performed over the same phase. The positive work performed by the tendon on sources other than muscle fibers during shortening is given as a percentage of the total work stored on the tendon during stretching in (f) and as percentage of the work stored on the tendon only due to the action of external sources with respect to the MTU in (g).