The influence of recruitment order and fibre composition on the force-velocity relationship and fatiguability of skeletal muscles in the cat

Two of the lower leg muscles of the cat were examined to assess the influence of the order in which motor units are recruited (slowest to fastest or fastest to slowest) and the fibre composition on the force-velocity relationship and fatiguability of skeletal muscle. The muscles examined were the soleus, a slow twitch muscle, and the medial head of the gastrocnemius muscle, a predominantly fast twitch muscle of mixed composition. The results of these experiments showed that the force-velocity relationship was a function of both the order of motor unit recruitment and the fibre composition of the muscles. However, at either recruitment order, the ability of the computer to control the velocity of contraction and the resultant fatiguability of the muscle for these contractions was similar.