5 Influence of Exercise and Training on Motor Unit Activation.

Human MUs vary considerably in twitch force, contractile speed, axonal conduction velocity, fatigue resistance, recruitment thresholds, firing rates, and firing patterns. These functional properties, together with the corresponding morphological characteristics such as soma size, axon diameter, and muscle fiber size, are interrelated. The smallest (soma size, axon diameter, muscle fiber size) MUs have the smallest twitch force, the slowest …