In untrained individuals, changes in lean body mass and muscle strength during the initial weeks of strength training are not influenced by protein supplementation. Protein supplementation promotes greater gains in lean body mass and muscle strength for both trained and untrained individuals as the intensity, frequency, and duration of strength training increases. Protein supplementation increases muscle strength and size during prolonged strength training in healthy adults. Increasing age reduces this effect; training experience increases this effect. Protein intakes at amounts greater than about 1.6 g/kg/day do not further contribute to gains in fat free mass.
The timing of administering the protein intake in reference to the training session has not been shown to change its outcomes, despite the widely held belief that pre- or post-workout supplementation is particularly effective.