Relationships between motor nerve conduction velocities and motor unit contraction characteristics in a slow twitch muscle of the cat.

1. Isometric contractions of cat soleus muscles and of functionally isolated motor units have been measured under conditions similar to those of Bagust, Knott, Lewis, Luck & Westerman (1973).2. The muscle lengths at which motor unit twitch and tetanus tensions were maximal were close to the optimal lengths of the parent muscles.3. Motor unit contraction times and tensions were shown to be related to the conduction velocities of the nerve axons supplying them. These relationships were obscured when a number of small samples from several experiments were grouped together.4. The ratios of the twitch to the tetanic tensions of the motor units were directly related to their times to peak tension.