Force loss induced by inhibiting cross-bridge cycling is mitigated in eccentric contraction.

We examined whether the force loss induced by 2,3-butanedione monoxime affects isometric and eccentric forces differently. Single skinned muscle fibers were activated at an average sarcomere length of 2.4 μm and then stretched to 3.0 μm. This trial was performed with and without 2,3-butanedione monoxime to calculate the magnitude of force loss attained at several time points: pre-stretch phase at 2.4 μm, eccentric phase, end of eccentric contraction, and post-stretch phase at 3.0 μm. The magnitude of force loss was significantly larger in the pre-stretch phase than at the other time points. Further, the mitigated force loss in the eccentric contraction was more prominent in the long condition than in the short condition. We suggest that the eccentric force is relatively preserved compared with the reference isometric force (pre-stretch) when cross-bridge cycling is inhibited, possibly because of the contribution of the elastic force produced by titin.