Glucose kinetics and exercise performance during phases of the menstrual cycle: effect of glucose ingestion

Abstract

To study the effect of menstrual cycle phase and carbohydrate ingestion on glucose kinetics and exercise performance, eight healthy, moderately trained, eumenorrheic women cycled at 70% of peak O(2) consumption for 2 h and then performed a 4 kJ/kg body wt time trial. A control (C) and a glucose ingestion (G) trial were completed during the follicular (F) and luteal (L) phases of the menstrual cycle. Plasma substrate concentrations were similar before the commencement of exercise. Glucose rates of appearance and disappearance were higher (P < 0.05) during the 2nd h of exercise in FC than in LC. The percent contribution of carbohydrate to total energy expenditure was greater in FC than in LC, and subjects performed better (13%, P < 0.05) in FC. Performance improved (19% and 26% in FG and LG compared with FC and LC, respectively, P < 0.05) with the ingestion of glucose throughout exercise. These data demonstrate that substrate metabolism and exercise performance are influenced by the menstrual cycle phase, but ingestion of glucose minimizes these effects.

No effect of menstrual cycle phase on glucose kinetics and fuel oxidation during moderate-intensity exercise

“…This is in agreement with other studies (3,7,11,26), which have measured exercise RER over a range of exercise intensities (from 35 to 80% ). Others have reported, however, that lipid oxidation is greater, and carbohydrate oxidation lower, in the luteal vs. early or midfollicular phases of the menstrual cycle (10,18,57). These latter studies do not show consistent findings with respect to the intensity of exercise at which such an effect may be observed.…”

“…Exercise nutrient utilization in women throughout the menstrual cycle has generally been characterized by the measurement of RER. Certain data suggest that there may be greater lipid oxidation and lower carbohydrate oxidation with mild-to moderately high-intensity exercise [<75% of maximal O 2 uptake ] performed in the luteal vs. follicular phase of the menstrual cycle (10,18,40,57), although this has not always been observed (3,7,11,27). In terms of exercise substrate changes and the associated neuroendocrine response, results are inconsistent regarding menstrual cycle effects (6,16,27,49).…”

“…The infusion rate of the glucose isotope was increased twofold to minimize changes in isotope enrichment (44). Blood samples were drawn after a 5-min warm-up (time 0 for steady-state exercise) and at 10,20,30,45, 60, 75, and 90 min of steady-state exercise. Plasma samples were analyzed for glucose enrichment.…”

Sport Nutrition and Youth

“…Moreover, glucose ingestion improved time trial performance by a 19 to 26% in trained women (Campbell et al 2001), but only 7% in trained men (Angus et al 2000), although differences in study design mean these values cannot be compared directly. A direct comparison of trained men and women, however, reported remarkably similar metabolic responses to CHO supplementation, with both groups experiencing an increased plasma glucose turnover and oxidation, which suppressed fat and endogenous CHO oxidation (Wallis et al 2006).…”

“…In adults, there is evidence that women may derive a greater benefit from CHO ingestion than men; women oxidise a greater relative proportion of exogenous CHO during endurance exercise, which spares more endogenous fuel (Campbell et al 2001;Riddell et al 2003).…”