Effects of cross-innervation and disuse on the twitch speed of fast and slow hindlimb muscles in the decerebellate cat

In adult cats, we have investigated how nerve cross-union between slow and fast muscle affects twitch contraction and half-relaxation times in the presence and absence of motor disuse, produced by complete decerebellation. Cerebellectomy abolished the slowing of cross-innervated fast muscle and diminished the amount of speeding up of cross-innervated slow muscle. The results are consistent with the idea that cross-innervation between fast and slow muscles affects contraction speed through changes in the patterns of muscle fiber activation.