Post-contraction errors in human force production are reduced by muscle stretch

Based on findings from a previous study of plantar-flexor muscles, the effect of a conditioning 25, 50 or 100% maximum voluntary contraction (m.v.c) of elbow flexor muscles on the accuracy of reproducing a learned criterion muscle force (2% m.v.c.) was investigated. Each conditioning induced a significant error in reproducing the criterion muscle force under conditions of no visual feed-back of force. As with plantar-flexor muscles, the error was consistently in the direction of a positive bias. The magnitude of the error co-varied with the magnitude of the previous contraction and, in all cases, decayed toward criterion force values over a 35s period. A brief muscle stretch, induced before subjects attempted the criterion force, reduced the size of the error but did not completely eliminate the bias. The findings provide indirect evidence of post-contraction potentiation of stretch relfex pathways. Residual post-contraction errors in force production after muscle stretch may be attributed to other central or peripheral factors such as, for example, potentiating effects of prior activation on submaximal tension production in skeletal muscle.