Purpose:The purpose of this study was to determine if a creatine supplement prevents the decrease in performance while consuming a low carbohydrate (CHO) diet during high-intensity exercise. Compared to the placebo group where the low CHO diet was expected to result in reduced exercise tolerance, it was hypothesized that creatine supplementation would offset the adverse side effects of a low CHO diet, as demonstrated by a similar or improved exercise capacity. Methods: Twenty healthy subjects (8 males, 12 females; 27 ± 7 yrs, ±SD) were randomly assigned to a low CHO plus creatine monohydrate supplement (L-CHO+Cr), low CHO diet and placebo (L-CHO) group, or control (CON). Each subject performed 2 high intensity exercise tolerance tests (HIETT) to fatigue at 90% peak power output (PPO), separated by a 10 days where the subject followed a low CHO diet (<30% total consumption). Subjects completed a progressive exercise test to volitional fatigue to establish baseline fitness determined as peak O2 uptake (VO2peak) and to determine 90% of the peak work. The HEITT was on a 1:1 ratio of 30-seconds at 90% peak work rate followed by 30-seconds of no load active recovery. Heart rate was collected at baseline and every interval during iv both exercise sessions. Subjects consumed a loading dose of creatine monohydrate (20 g/day) or placebo (5g/day), while adhering to a low-CHO diet of <30% CHO total daily consumption. Subjects kept detailed food and exercise logs for the duration of the study. Results:The L-CHO+Cr group was of a similar fitness (36.1 ± 5.3 ml/kg/min) compared to the L-CHO group (36.9 ± 5.8 ml/kg/min) as determined by the progressive test to volitional fatigue. There was a statistically significant difference between the L-CHO+Cr group and the L-CHO HEITT performance pre-and post-dietary intervention (p=0.001).On average the L-CHO+Cr group demonstrated a 20% increase in the total number of bouts performed (pre/post), whereas the placebo group exhibited a 36% decrease. Both groups exhibited an average body fat loss of 1.0%, which was not statistically significant. Conclusion:The results of the present study demonstrated that a creatine loading protocol attenuates the fatigue associated with consuming a diet low in carbohydrate content, and indeed, leads to an improvement in high-intensity interval exercise performance. While the specific mechanism(s) underlying the improvement in performance was not identified in the present study, these findings are consistent with the results of studied demonstrating a significant relationship between the rate of phosphocreatine utilization following a dietary intervention and exercise performance. v
CONCLUSIONS:These results demonstrate a very small, but potentially important placebo effect with nutritional supplementation studies. A substantive proportion of supplement effects may be due to placebo effects, with the relative proportion influenced by the magnitude of the overall ergogenic effect. Where feasible, intervention studies should employ non-placebo controlarm comparators to identify the proportion of the effect estimated to come from placebo effects and avoid underestimating the overall benefits that the physiological plus psychobiological aspects associated with an intervention provide in the real world.
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