Effects of creatine on body composition and strength gains after 4 weeks of resistance training in previously nonresistance-trained humans.

This study examined the effects of Cr supplementation on muscle strength in conjunction with resistance training in nonresistance-trained males utilizing strategies previously reported in the literature to help optimize muscle CR uptake. Nineteen nonresistance-trained males underwent 4 weeks of resistance training (3 days x week(-1)) while assigned to Cr (20 g x d(-1) Cr + 140 g x d(-1) glucose) for 7 days (loading), followed by 5 g x d(-1) Cr + 35 g x d(-1) glucose for 21 days (maintenance; n = 9) or placebo (160 g x d(-1) glucose [loading] followed by 40 g x d(-1) [maintenance; n = 10]). In subjects classified as "responders" to Cr on the basis of body mass changes (n = 7), the magnitude of change in 180 degrees x s(-1) isokinetic (p = .029) and isometric (p = .036) force was greater compared to the placebo group. A positive correlation was found between changes in body mass and 180 degrees x s(-1) isokinetic (loading: r = 0.68, p = .04; maintenance: r = 0.70, p = .037) and isometric (loading: r = 0.82, p < .01) force. Estimated Cr uptake was also positively correlated with changes in isometric force (r = 0.71, p = .033). These results indicate that Cr supplementation can increase muscle strength (allied with 4 weeks of strength training) but only in subjects whose estimated Cr uptake and body mass are significantly increased; the greater the Cr uptake and associated body mass changes, the greater the performance gains.