Effect of oral creatine supplementation on isokinetic torque production

Purpose: This study was conducted to examine the effect of oral creatine su pplementation on the decline in peak isokinetic torque of the quadriceps mu scle group during an endurance test. Methods: Twenty-three active, but untr ained, male subjects performed isokinetic strength tests on a Cybex ZI dyna mometer at 180 degrees.s(-1) The protocol consisted of pre- and post-tests with five sets of 30 maximum volitional contractions with a 1-min rest peri od between sets. Subjects returned to perform the posttest after 5 d of pla cebo (4 x 6g glucose.d(-1), N = 12) or creatine (4 x 5g creatine + 1 g gluc ose d(-1), N = 11) supplementation. Supplements and testing were administer ed in a double blind fashion. Peak torque was measured during each contract ion and the 30 contractions were averaged for each set. Results: A three-wa y mixed ANOVA with one between factor (placebo vs creatine) and two within factors (pre/post supplementation and sets 1-5) revealed no significant int eractions, P > 0.05. The placebo vs creatine main effect was also nonsignif icant, whereas the pre/post and set effects were significant (P < 0.05). Pe ak torque increased (similar to 3%) from pre- to post-testing, (P = 0.04), but the absolute magnitude of the differences is unlikely to be of any prac tical significance. Peak torque decreased from sets 1 to 4, whereas sets 4 and 5 were not different. A priori contrasts comparing the creatine group's performance pre vs post test for the fourth and fifth sets were nonsignifi cant (P > 0.05). Conclusions: Based on within and between group comparisons , we were unable to detect an ergogenic effect of oral creatine supplementa tion on the decline in peak torque during isokinetic exercise at 180 degree s.s(-1).