Effect of creatine loading on anaerobic performance and skeletal muscle volume in NCAA division I athletes

Abstract

OBJECTIVE: We measured the effect of 3 d of creatine (Cr) supplementation on repeated sprint performance and thigh muscle volume in elite power athletes.

METHODS: Ten male (mean ± standard deviation of body mass and percentage of fat (81.1 ± 10.5 kg and 9.8 ± 3.5) and ten female (58.4 ± 5.3 kg and 15.0 ± 3.4) athletes were matched for sex and 10-s cycle sprint scores, paired by rank, and randomly assigned to the Cr or placebo (P) group. Subjects completed six maximal 10-s cycle sprints interspersed with 60 s of recovery before and after 3 d of Cr (0.35 g/kg of fat-free mass) or P (maltodextrin) ingestion. Before and after supplementation, 10 contiguous transaxial images of both thighs were obtained with magnetic resonance imaging.

RESULTS: Cr supplementation resulted in statistically significant increases in body mass (0.9 ± 0.1 kg, P < 0.03), total work during the first sprint (P < 0.04), and peak power during sprints 2 to 6 (P < 0.10). As expected, total work and peak power values for males were greater than those for their female counterparts during the initial sprint (P < 0.02); however, the reverse was true during the last three sprints (P < 0.01). Imaging data showed a 6.6% increase in thigh volume in five of six Cr subjects (P = 0.05).

CONCLUSION: These data indicate that 3 d of Cr supplementation can increase thigh muscle volume and may enhance cycle sprint performance in elite power athletes; moreover, this effect is greater in females as sprints are repeated.

Introduction

Exogenous creatine (Cr) feedings (20 g/d × 5–6 d) can add to the body’s total creatine pool,1, 2 and up to 30% of this exists as phosphocreatine (PCr). Performance benefits have included increases in peak isokinetic knee2 and isometric ankle extension and reductions in fatigue during dynamic and isometric exercise.3, 4, 5

Interestingly, not all studies have shown a performance improvement with Cr supplementation. For instance, reports using swimming6 and running7 showed no benefit with Cr supplementation. Further, an investigation by Cooke et al.8 found no effect of Cr during a single bout of cycling exercise. The underlying reasons for equivocal results are unclear but may be related to design or statistical issues (e.g., lack of a control group, use of repeated t tests with no experimentwise correction, or the use of lengthy rest periods between repeated tests) in some of these studies.

Moreover, there is a dearth of published information on Cr supplementation in elite competitive athletes, particularly those involved in power sports (e.g., wrestling, hockey, basketball, and sprinting). We previously observed increased (14%) resting PCr/ATP (³¹P magnetic resonance spectroscopy) within 48 to 72 h of Cr supplementation (20 g/d), resulting in ergogenic effects during intense repeated muscle contraction in untrained males.3, 9 Thus, we investigated whether 3 d of Cr supplementation in elite power athletes would affect sprint cycle performance and thigh muscle volume.