Abstract
The purpose was to examine the effects of creatine supplementation during resistance training sessions on skeletal muscle mass and exercise performance in physically active young adults. Twenty-two participants were randomized to supplement with creatine (CR: n = 13, 26 ± 4 yrs; 0.0055 g·kg−1 post training set) or placebo (PLA: n = 9, 26 ± 5 yrs; 0.0055 g·kg−1 post training set) during six weeks of resistance training (18 sets per training session; five days per week). Prior to and following training and supplementation, measurements were made for muscle thickness (elbow and knee flexors/extensors, ankle plantarflexors), power (vertical jump and medicine ball throw), strength (leg press and chest press one-repetition maximum (1-RM)) and muscular endurance (one set of repetitions to volitional fatigue using 50% baseline 1-RM for leg press and chest press). The creatine group experienced a significant increase (p < 0.05) in leg press, chest press and total body strength and leg press endurance with no significant changes in the PLA group. Both groups improved total body endurance over time (p < 0.05), with greater gains observed in the creatine group. In conclusion, creatine ingestion during resistance training sessions is a viable strategy for improving muscle strength and some indices of muscle endurance in physically active young adults.
Highlights
Creatine is an organic compound naturally produced in the body from reactions involving the amino acids arginine, glycine and methionine in the kidneys and liver or consumed in the diet primarily from red meat, poultry, seafood [1] or supplementation practices
On the non-training days, participants refrained from consuming creatine or placebo as the purpose of the study was to investigate the effects of creatine ingestion during resistance training sessions
One female in the creatine group reported gastrointestinal irritation during the first week of creatine supplementation but this did not result in her withdrawing from the study
Summary
Creatine is an organic compound naturally produced in the body from reactions involving the amino acids arginine, glycine and methionine in the kidneys and liver or consumed in the diet primarily from red meat, poultry, seafood [1] or supplementation practices. There is substantial evidence that creatine supplementation and resistance training increases muscle mass and performance (i.e., strength) more than placebo and resistance training, possibly by influencing phosphate metabolism, cellular hydration status, calcium and protein kinetics, glycogen content, satellite cells, growth factors, inflammation and oxidative stress (for reviews see [2,3,4,5,6]). Ingesting creatine immediately following each set of resistance training may increase creatine uptake into skeletal muscle, which over time could lead to greater gains in muscle mass and performance compared to placebo. It was hypothesized that the repeated ingestion of creatine following each set of resistance training would lead to greater gains in muscle mass and performance compared to placebo immediately following each set of resistance training
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