Muscle growth

Muscle hypertrophy involves an increase in size of skeletal muscle through a growth in size of its component cells. Two factors contribute to hypertrophy: sarcoplasmic hypertrophy, which focuses more on increased muscle glycogen storage; and myofibrillar hypertrophy, which focuses more on increased myofibril size.

A range of stimuli can increase the volume of muscle cells. These changes occur as an adaptive response that serves to increase the ability to generate force or resist fatigue in anaerobic conditions.

Strength training typically produces a combination of the two different types of hypertrophy: contraction against 80 to 90% of the one-repetition maximum for 2–6 repetitions (reps) causes myofibrillated hypertrophy to dominate (as in powerlifters, Olympic lifters and strength athletes), whereas several repetitions (generally 8–12 for bodybuilding or 12 or more for muscular endurance) against a submaximal load facilitates mainly sarcoplasmic hypertrophy (professional bodybuilders and endurance athletes).

Progressive overload is one method of training used in muscle hypertrophy. Early muscle growth has been studied and has some association with the implementation of a muscle resistance training program.

The best approach to specifically achieve muscle growth remains controversial (as opposed to focusing on gaining strength, power, or endurance); it was generally considered that consistent anaerobic strength training will produce hypertrophy over the long term, in addition to its effects on muscular strength and endurance. Muscular hypertrophy can be increased through strength training and other short-duration, high-intensity anaerobic exercises. Lower-intensity, longer-duration aerobic exercise generally does not result in very effective tissue hypertrophy; instead, endurance athletes enhance storage of fats and carbohydrates within the muscles, as well as neovascularization.

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