Determining load according to fiber type

This is an excerpt from Science and Development of Muscle Hypertrophy by Brad Schoenfeld.

Load

Practical Applications

Hypertrophy can be achieved in all loading zones. Low-load training emphasizes metabolic stress and promotes the greatest increases in local muscular endurance, whereas low-repetition, high-load training requires high mechanical tension and enhances the ability to lift heavier loads as a result of greater neural adaptations. There appears to be a fiber type - specific response in which heavy-load training produces greater cross-sectional area increases in Type II fibers and light loads have a preferential effect on Type I hypertrophy. Thus, if the primary goal is maximizing hypertrophy without regard to strength-related factors, then training across a wide spectrum of repetition ranges (1 through 20+) is recommended to exploit all possible avenues for the complete development of the whole muscle. There is merit to focusing on a medium-repetition range (6- to 12RM), because it provides high levels of mechanical tension sufficient to stimulate the full array of fiber types while allowing for sufficient training volumes. Incorporating heavy loading (1- to 5RM) enhances strength, which ultimately allows the use of heavier loads during medium-repetition lifting. Additionally, light-load training should be included both to ensure the optimal development of Type I fibers and to improve the buffering capacity of muscle so that additional repetitions can be performed at a given medium intensity of load.

On the other hand, if the goal is to promote hypertrophy to maximize strength, there appears little reason to employ loads less than approximately 70% of 1RM. The compelling body of research indicates the presence of a strength - endurance continuum, in which lighter loads promote the ability to carry out submaximal resistive efforts at the expense of maximal force production. Increases in Type I fiber hypertrophy, as would be expected when training with low loads, have limited transfer to strength-related improvements.

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