Introduction: Creatine- and carbohydrate-loading are dietary strategies used to enhance exercise capacity. This study examined the metabolic and performance effects of a combined creatine and CHO-loading regiment on time-trial (TT) cycling bouts.
Methods: Eighteen well-trained (~65mL[BULLET OPERATOR]kg-1[BULLET OPERATOR]min-1 VO2peak) males completed three performance trials (PT) comprised of a 120-km cycling TT interspersed with alternating 1- and 4-km sprints (6 sprints each) performed every 10-km followed by an inclined ride to fatigue (~90% VO2peak). Subjects were pair-matched into either creatine-loaded (20g[BULLET OPERATOR]d-1 for 5d + 3 g[BULLET OPERATOR]d-1 for 9d; CR) or placebo (PLA) groups (n=9) following the completion of PT1. All subjects undertook a cross-over application of the carbohydrate interventions, consuming either moderate-(6g[BULLET OPERATOR]kg-1 body mass (BM)/d; MOD) or CHO-loaded (12g[BULLET OPERATOR]kg-1 BM/d; LOAD) diets before PT2 and PT3. Muscle biopsies were taken prior to PT1, 18h post-PT1, and prior to both PT2 and PT3.
Results: No significant differences in overall TT or inclined ride times were observed between intervention groups. PLA+LOAD improved power above baseline (P<0.05) during the final 1-km sprint whereas CR+ MOD and CR+LOAD improved power (P<0.05) during the final 4-km sprint. Greater power was achieved with MOD and LOAD compared to baseline with PLA (P<0.05). CR increased pre-PT BM compared to PLA (+1.54% vs +0.99% from baseline). CR+LOAD facilitated greater [total creatine] (P<0.05 vs. baseline) and muscle [glycogen] (P<0.01 vs. baseline and MOD) compared to PLA+LOAD. Mechanistic target of rapamycin (mTOR) decreased from baseline following glycogen depletion (~30%; P< 0.05).
Conclusion: Power output in the closing sprints of exhaustive time-trial cycling increased with creatine ingestion despite a creatine-mediated increase in weight. Creatine co-supplemented with carbohydrates may therefore be beneficial strategy for late-stage breakaway moments in endurance events.
(C) 2017 American College of Sports Medicine