How low and high carbohydrate diets affect 45 minutes of hard cycling

Muscle glycogen levels were significantly higher in the high carbohydrate (H-CHO) trial at 104.5 +/- 9.4 mmol/kg wet wt compared to the low carbohydrate (L-CHO) trial at 72.2 +/- 5.6 mmol/kg wet wt.

• Serum glucose levels increased significantly during exercise in the H-CHO trial, rising from 4.5 +/- 0.1 mmol x L(-1) (pre) to 6.7 +/- 0.6 mmol x L(-1) (post).
• Post-exercise serum glucose was also significantly greater for the H-CHO trial compared to L-CHO (H-CHO: 6.7 +/- 0.6 mmol x L(-1); L-CHO: 5.2 +/- 0.2 mmol x L(-1)).
• Heart rate, perceived exertion, oxygen uptake, and respiratory quotient did not differ significantly between the two dietary trials.
• No significant changes were observed in serum free fatty acids, triglycerides, or insulin concentrations in either trial.
• The findings indicate that the low carbohydrate diet did not significantly affect 45-minute cycling exercise performance when total energy intake was adequate.

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