[Comparison of the increase of stiffness produced during sinusoidal stretch of the long fibula muscle in the cat by the contraction of slow or fast motor units].

The increase in stiffness of cat peroneus longus muscle elicited by the contraction of homogeneous groups of motor units (slow, fast fatigue-resistant and fast fatigable) was measured during sinusoidal stretches (20-80 Hz) of small amplitude (40-100 micron). For comparable tetanic tensions, slow units increase muscle stiffness more than fast unit.