Carbohydrate supplementation spares muscle glycogen during variable-intensity exercise

Oct 1, 1993Journal of applied physiology (Bethesda, Md. : 1985)

Carbohydrate supplements help preserve muscle energy stores during changing exercise intensity

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Plasma glucose levels reached 6.7 +/- 0.7 mM during carbohydrate supplementation, significantly higher than the placebo group.

Carbohydrate supplementation resulted in greater plasma insulin levels compared to placebo, with levels of 70.6 +/- 17.2 microU/ml versus 17.7 +/- 1.6 microU/ml.
Muscle glycogen concentrations were significantly higher during carbohydrate supplementation (79 +/- 3.5 mumol/g wet wt) compared to placebo (58.5 +/- 7.2 mumol/g wet wt).
Time to fatigue was significantly longer with carbohydrate treatments (S: 223.9 +/- 3.5 min; L: 233.4 +/- 7.5 min) compared to placebo (202.4 +/- 9.8 min).
Positive correlations were observed between muscle glycogen levels after 190 min of exercise and time to fatigue for carbohydrate versus placebo treatments (r = 0.76, P < 0.05).
Carbohydrate supplementation may enhance endurance during prolonged variable-intensity exercise by reducing reliance on muscle glycogen.

AI simplified

Effects of carbohydrate (CHO) supplementation on muscle glycogen utilization and endurance were evaluated in seven well-trained male cyclists during continuous cycling exercise that varied between low [45% maximal O2 uptake (VO2 max)] and moderate intensity (75% VO2 max). During each exercise bout the subjects received either artificially flavored placebo (P), 10% liquid CHO supplement (L; 3 x 18 g CHO/h), or solid CHO supplement (S; 2 x 25 g CHO/h). Muscle biopsies were taken from vastus lateralis during P and L trials immediately before exercise and after first (124 min) and second set (190 min) of intervals. Subjects then rode to fatigue at 80% VO2 max. Plasma glucose and insulin responses during L treatment reached levels of 6.7 +/- 0.7 mM and 70.6 +/- 17.2 microU/ml, respectively, and were significantly greater than those of P treatment (4.4 +/- 0.1 mM and 17.7 +/- 1.6 microU/ml) throughout the exercise bout. Plasma glucose and insulin responses of S treatment were intermediate to those of L and P treatments. Times to fatigue for S (223.9 +/- 3.5 min) and L (233.4 +/- 7.5 min) treatments did not differ but were significantly greater than that of P treatment (202.4 +/- 9.8 min). After the first 190 min of exercise, muscle glycogen was significantly greater during L (79 +/- 3.5 mumol/g wet wt) than during P treatment (58.5 +/- 7.2 mumol/g wet wt). Furthermore, differences in muscle glycogen concentrations between L and P treatments after 190 min of exercise and in time to fatigue for these treatments were positively related (r = 0.76, P < 0.05). These results suggest that CHO supplementation can enhance prolonged continuous variable-intensity exercise by reducing dependency on muscle glycogen as a fuel source.

Full Text

Full text is available at the source.

View full text ↗

Carbohydrate supplementation spares muscle glycogen during variable-intensity exercise

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief