Muscle glycogen storage following prolonged exercise: effect of timing of ingestion of high glycemic index food.
Level 2 - randomized trial
Small human crossover trial measuring physiological outcomes across repeated conditions.
PubMed 9044226 · doi:10.1097/00005768-199702000-00009
What was done
Six endurance-trained men performed exhaustive cycling exercise (2 hours at 70% VO2max followed by four 30-second sprints) on two separate occasions. Following exercise, participants consumed five high glycemic index meals over 24 hours, receiving the first three meals either immediately (0 to 4 hours post-exercise at 2-hour intervals) or delayed (2 to 6 hours post-exercise). Muscle biopsies were taken immediately after exercise and at 8 and 24 hours post-exercise to measure glycogen and glucose-6-phosphate. Blood glucose and insulin were sampled before and 30, 60, and 90 minutes after each meal.
What was found
The abstract reports no numerical values. It found no significant differences between the immediate and delayed feeding trials in incremental glucose or insulin areas under the curve after meals, nor any differences in muscle glycogen or glucose-6-phosphate concentrations at 8 or 24 hours post-exercise.
Why it matters
The findings suggest that when total carbohydrate intake across a 24-hour recovery period is adequate, delaying the start of carbohydrate ingestion by 2 hours does not compromise intermediate (8-hour) or next-day (24-hour) muscle glycogen restoration.
Limits
The sample size was extremely small (n = 6) and limited exclusively to endurance-trained men. The abstract does not state whether the trial order was randomized, nor does it provide exact numerical data, confidence intervals, or total carbohydrate amounts. Glycogen resynthesis in the immediate early window (under 8 hours) was not directly biopsied.
Cited by
- context The faster carbohydrate is ingested post-exercise, the faster muscle and liver glycogen stores are replenished.