Effect of 28 days of creatine ingestion on muscle metabolism and performance of a simulated cycling road race

Robert C Hickner,Holly Hatley,Josh Sklar,Priscilla Byrd,David J Dyck

doi:10.1186/1550-2783-7-26

Abstract

PurposeThe effects of creatine supplementation on muscle metabolism and exercise performance during a simulated endurance road race was investigated.MethodsTwelve adult male (27.3 ± 1.0 yr, 178.6 ± 1.4 cm, 78.0 ± 2.5 kg, 8.9 ± 1.1 %fat) endurance-trained (53.3 ± 2.0 ml* kg-1* min-1, cycling ~160 km/wk) cyclists completed a simulated road race on a cycle ergometer (Lode), consisting of a two-hour cycling bout at 60% of peak aerobic capacity (VO2peak) with three 10-second sprints performed at 110% VO2 peak every 15 minutes. Cyclists completed the 2-hr cycling bout before and after dietary creatine monohydrate or placebo supplementation (3 g/day for 28 days). Muscle biopsies were taken at rest and five minutes before the end of the two-hour ride.ResultsThere was a 24.5 ± 10.0% increase in resting muscle total creatine and 38.4 ± 23.9% increase in muscle creatine phosphate in the creatine group (P < 0.05). Plasma glucose, blood lactate, and respiratory exchange ratio during the 2-hour ride, as well as VO2 peak, were not affected by creatine supplementation. Submaximal oxygen consumption near the end of the two-hour ride was decreased by approximately 10% by creatine supplementation (P < 0.05). Changes in plasma volume from pre- to post-supplementation were significantly greater in the creatine group (+14.0 ± 6.3%) than the placebo group (-10.4 ± 4.4%; P < 0.05) at 90 minutes of exercise. The time of the final sprint to exhaustion at the end of the 2-hour cycling bout was not affected by creatine supplementation (creatine pre, 64.4 ± 13.5s; creatine post, 88.8 ± 24.6s; placebo pre, 69.0 ± 24.8s; placebo post 92.8 ± 31.2s: creatine vs. placebo not significant). Power output for the final sprint was increased by ~33% in both groups (creatine vs. placebo not significant).ConclusionsIt can be concluded that although creatine supplementation may increase resting muscle total creatine, muscle creatine phosphate, and plasma volume, and may lead to a reduction in oxygen consumption during submaximal exercise, creatine supplementation does not improve sprint performance at the end of endurance cycling exercise.

Highlights

Muscle creatine phosphate content has been shown to decline during prolonged exercise at 70% VO2max [1,2]
Changes in plasma volume from pre- to post-supplementation were significantly greater in the creatine group (+14.0 ± 6.3%) than the placebo group (-10.4 ± 4.4%; P < 0.05) at 90 minutes of exercise
We have found that 28 days of creatine supplementation at three g/day increases muscle creatine phosphate to levels above a placebo group post supplementation

Summary

Introduction

Muscle creatine phosphate content has been shown to decline during prolonged exercise at 70% VO2max [1,2] It is well-established that dietary creatine supplementation can increase muscle creatine phosphate content and creatine phosphate resynthesis rates; thereby improving high-intensity intermittent exercise performance [3,4,5,6]. Some of the studies were not double blind, randomized, or performed with a placebo; muscle biopsies were obtained to document increased muscle creatine phosphate stores in only one of these previous studies Exercise in these previous studies was performed following 5-7 days ingestion of 20 grams per day of a creatine supplement

Methods

Results

Discussion

Conclusion