Abstract
Carbohydrates are critical for high- intensity exercise performance. However, the effects of carbohydrate supplementation on muscle metabolism and performance during short- duration high- intensity intermittent exercise remain inadequately explored. Our aim was to address this aspect in a randomized, counterbalanced, double- blinded crossover design. Eleven moderately-
to- well-trained males performed high-intensity intermittent cycling receiving carbohydrate (CHO, ~55 g/h) or placebo (PLA) fluid supplementation. Three exercise periods (EX1- EX3) were completed comprising 10 × 45 s at ~105% Wmax interspersed with 135 s rest between bouts and ~20 min between periods. Repeated sprint ability (5 × 6 s sprints with 24 s recovery) was assessed at
baseline and after each period. Thigh muscle biopsies were obtained at baseline and before and after EX3 to determine whole-muscle and fiber- type- specific glycogen depletion. No differences were found in muscle glycogen degradation at the whole-muscle (p = 0.683) or fiber- type- specific level (p = 0.763–0.854) with similar post- exercise whole- muscle glycogen concentrations (146 ± 20 and 122 ± 15 mmol·kg−1 dw in CHO and PLA, respectively). Repeated sprint ability declined by ~9% after EX3 with no between- condition differences (p = 0.971) and no overall differences in ratings of perceived exertion (p = 0.550). This was despite
distinctions in blood glucose concentrations throughout exercise, reaching post- exercise levels of 5.3 ± 0.2 and 4.1 ± 0.2 mmol·L−1 (p < 0.001) in CHO and PLA, respectively, accompanied by fivefold higher plasma insulin levels in CHO (p < 0.001). In conclusion, we observed no effects of carbohydrate ingestion on net muscle glycogen breakdown or sprint performance during short-duration high- intensity intermittent exercise despite elevated blood glucose and insulin levels. These results therefore question the efficacy of carbohydrate supplementation strategies in high- intensity intermittent sports.
to- well-trained males performed high-intensity intermittent cycling receiving carbohydrate (CHO, ~55 g/h) or placebo (PLA) fluid supplementation. Three exercise periods (EX1- EX3) were completed comprising 10 × 45 s at ~105% Wmax interspersed with 135 s rest between bouts and ~20 min between periods. Repeated sprint ability (5 × 6 s sprints with 24 s recovery) was assessed at
baseline and after each period. Thigh muscle biopsies were obtained at baseline and before and after EX3 to determine whole-muscle and fiber- type- specific glycogen depletion. No differences were found in muscle glycogen degradation at the whole-muscle (p = 0.683) or fiber- type- specific level (p = 0.763–0.854) with similar post- exercise whole- muscle glycogen concentrations (146 ± 20 and 122 ± 15 mmol·kg−1 dw in CHO and PLA, respectively). Repeated sprint ability declined by ~9% after EX3 with no between- condition differences (p = 0.971) and no overall differences in ratings of perceived exertion (p = 0.550). This was despite
distinctions in blood glucose concentrations throughout exercise, reaching post- exercise levels of 5.3 ± 0.2 and 4.1 ± 0.2 mmol·L−1 (p < 0.001) in CHO and PLA, respectively, accompanied by fivefold higher plasma insulin levels in CHO (p < 0.001). In conclusion, we observed no effects of carbohydrate ingestion on net muscle glycogen breakdown or sprint performance during short-duration high- intensity intermittent exercise despite elevated blood glucose and insulin levels. These results therefore question the efficacy of carbohydrate supplementation strategies in high- intensity intermittent sports.
| Original language | English |
|---|---|
| Article number | e14731 |
| Number of pages | 14 |
| Journal | Scandinavian Journal of Medicine & Science in Sports |
| Volume | 34 |
| Issue number | 9 |
| Publication status | Published - 22 Sept 2024 |
Keywords
- ergogenic aids
- fiber type
- glycogen
- sprint ability
- substrate
