Eccentric muscle contractions are part of our daily lives. In this study, we found that force increased monotonically during slow stretches of fully activated muscle fibers, whereas higher stretch velocities resulted in an increasing drop in force after an initial increase and a final steeper rise in force. Cross-bridges cannot explain the observed force traces. This requires a viscoelastic non-cross-bridge (titin) contribution. Considering these results can improve muscle models and predictions of multibody simulations.
This research was funded by the Deutsche Forschungsgemeinschaft (DFG) under Grant SI841/17-1 and partially funded by the DFG as part of the German Excellence Strategy—EXC 2075—390740016.