What type of exercise is best for muscle gain?

Resistance exercise is the most effective type of exercise for muscle gain.^[1][2] Performing sets to muscular failure (i.e., the point at which another repetition cannot be completed while maintaining proper form) is just as effective as ending sets a few repetitions away from muscular failure when moderate to heavy loads (60–90% of one-repetition maximum) are used,^[3] but sets should be performed to muscular failure when light loads (30–40% of one-repetition maximum) are used.^[4] Training frequency doesn’t seem to meaningfully affect muscle gain as long as the amount of volume performed is the same,^[5] but a high training frequency (e.g., training a muscle group three times per week) may be particularly advantageous when performing a high-volume training program.^[6][7]