Effects of Muscle Glycogen on Performance of Repeated Sprints and Mechanisms of Fatigue

Baseline muscle glycogen levels were 346 ± 19 mmol/kg dw after a high carbohydrate diet compared to 222 ± 19 mmol/kg dw after a low carbohydrate diet.

• Total exercise time to 30% fatigue was higher following high carbohydrate intake (57.5 ± 10.0 min) compared to low carbohydrate intake (42.0 ± 3.6 min).
• Muscle glycogen levels decreased by 43%, creatine phosphate levels by 35%, and sarcoplasmic reticulum calcium uptake by 56% during the exercise bouts.
• The percentage decline in sarcoplasmic reticulum calcium release was lower after high carbohydrate intake (36%) compared to low carbohydrate intake (53%), although this difference was not statistically significant.
• High carbohydrate intake is associated with delayed fatigue during repeated sprints.
• Reductions in muscle glycogen, creatine phosphate, and sarcoplasmic reticulum function during exercise were similar regardless of dietary treatment.

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