Written by Anssi Manninen
01 May 2007
In a recent study by Dr. Jay Hoffman and colleagues at the College of New Jersey, the effects of protein supplementation on athletic performance and hormonal changes were examined in 21 experienced collegiate gym rats participating in a 12-week resistance-training program. Subjects were randomly assigned to either a protein supplement or a placebo (fake supplement) group.

mr-157.jpgThe protein group used MET-Rx®, which provided 260 kilocalories, 42 grams of protein, 18 grams of carbs and 3 grams of fat per serving. Subjects consumed one drink every morning and a second daily drink following their exercise session. The placebo group consumed a supplement which contained mainly carbs (maltodextrine). During each testing session, subjects were assessed for strength (bench press and squat max), power (Wingate anaerobic power test) and body composition. Wingate is a 30-second test performed at a maximal effort against a resistance relative to the subject´s bodyweight, providing an assessment of the ability to maintain high-power output over a relatively long duration. In addition, blood samples were analyzed for total testosterone, cortisol, growth hormone (GH) and IGF-1.

The results indicated that protein supplementation augmented lower body strength development. Furthermore, higher protein intakes were associated with a trend toward an increase in lean body mass. As pointed out by the authors, the energy intakes seen in this study were low in comparison to what is generally recommended for serious gym rats. This may- at least partially- explain the inability to achieve statistically significant increases in lean tissue accruement. Finally, protein supplementation did not affect T, GH, cortisol or IGF-1 levels.




Hoffman JR et al. J Sports Sci Med 2007;6:85 - 92.