Increases in strength can be re-educated into a sports action. A large part of strength training is skill acquisition. Adaptation may even be purely specific to the joint angle at which training occurs. In some studies fast training has produced almost the same results as low-velocity training while others have shown the velocity to be specific, that is, slow training improves slow movements and fast training improves fast movements. Slow velocity training enlarges both types of muscle fibers.
Greater hypertrophy occurs in fast-twitch fibers, probably because they are more reactive.
Provided the degree of effort is maximal, the motor unit activation is similar regardless of the contraction velocity. Fast-twitch fibers are activated even in isometric contractions. Fast-twitch fibers are designed to contribute to force, regardless of velocity. The specificity of velocity in strength is related to the organization of movements by the brain rather than to selective recruitment of motor unit types. Low loads, high repetitions do not produce muscle enlargement unless the original starting level was particularly poor.