I recently read a paper by Gabriel et al. (2008) titled, Dynamic joint stiffness of the ankle during walking: Gender-related differences. In this paper, the authors presented plots of ankle moment of force plotted against ankle joint angle during stance:

Ankle_mom_vs_angle_1.jpg.

I did a quick version of this with some data I had:

Ankle_mom_vs_angle_2.jpg.

Would I be correct in interpreting these curves as showing the hysteresis of the ankle joint plantarflexor muscles, in which case the region between the loading and unloading portions of the curves would represent the loss of energy during the stance phase (in the case of our data, that area is roughly 3.9 J/kg)? Would this energy be lost as heat or would it, in fact, be part of the energy that is transferred to the shank via the gastrocnemius? Or am I completely wrong here?

Thanks for any discussion on this.

Gabriel RC, Abrantes J, Granata K, Bulas-Cruz J, Melo-Pintod P, Filipe V. Dynamic joint stiffness of the ankle during walking: Gender-related differences, Physical Therapy in Sport 9 (2008) 1624