Dietary creatine supplementation and muscular adaptation to resistive overload

Purpose: This study examined the influence of dietary creatine (CR) supplem entation upon mechanical and hypertrophic responses to a well-defined condi tioning stimulus provided by electromyostimulation (EMS). Methods: Eighteen resistance-trained subjects were assigned CR or a placebo (PL) in a random ized, double-blind fashion. After CR loading (20 g.d(-1) for 7 d), CR suppl ementation (5 g.d(-1)) or PL was continued for 8 wk. During supplementation , EMS (3-5 sets of 10 coupled eccentric and concentric actions) was applied to the left in. quadriceps femoris (QF) twice weekly while subjects contin ued voluntary resistance training of both lower limbs unsupervised. Cross-s ectional area (CSA) of each QF was assessed with magnetic resonance imaging (MRI). Torque during EMS was analyzed to assess muscle loading and fatigue resistance. Results: Maximal torque and the torque time integral increased markedly over training (P less than or equal to 0.0001). These responses r eflected activation of more muscle as EMS current was increased (about 16%) , greater recovery between sets (P less than or equal to 0.0423), and less fatigue during sets over training (P = 0.0002). CR did not influence these responses (P = 0.8093). In accord with these results, the increase in CSA f or the stimulated QF (11%) was comparable for CR and PL (P = 0.2190). CSA i n the nonstimulated QF increased 5% in CR (P = 0.0091) but did not change i n PL. Conclusion: We conclude that CR supplementation did not augment the m echanical or hypertrophic response to a precisely measured conditioning sti mulus that attenuated but did not ameliorate fatigue. We suggest that enhan ced fatigue resistance may not explain the apparent ergogenic effect of CR during voluntary training.