Supplementing with creatine enhances resistance-exercise-induced gains in lean mass and upper- and lower-body strength.[1] Some evidence suggests that supplementing with whey protein and/or vitamin D can enhance certain measures of muscle strength and physical performance.[2][3][4] Also, supplementing with omega-3 fatty acids may enhance improvements in performance on the TUG test.[5]
In longitudinal trials, supplementing with leucine has not been found to enhance resistance-exercise-induced gains in muscle mass, muscle strength, or physical performance.[6][7] However, supplementing a suboptimal dose of protein (10–20 grams) with leucine has been shown to enhance rates of muscle protein synthesis,[8][9][10][11] so leucine may augment the benefits of resistance exercise in the context of a diet with suboptimal protein content, but further research is needed.