Women at altitude: Carbohydrate utilization during exercise at 4,300 m

Barry Braun, Jacinda T. Mawson, Stephen R. Muza, Shannon B. Dominick, George A. Brooks, Michael A. Horning, Paul B. Rock, Lorna G. Moore, Robert S. Mazzeo, Steven C. Ezeji-Okoye, Gail E. Butterfield

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Abstract

To evaluate the hypothesis that exposure to high altitude would reduce blood glucose and total carbohydrate utilization relative to sea level (SL), 16 young women were studied over four 12-day periods: at 50% of peak O2 consumption in different menstrual cycle phases (SL-50), at 65% of peak O2 consumption at SL (SL-65), and at 4,300 m (HA). After 10 days in each condition, blood glucose rate of disappearance (R(d)) and respiratory exchange ratio were measured at rest and during 45 min of exercise. Glucose R(d) during exercise at HA (4.71 ± 0.30 mg·kg-1·min-1) was not different from SL exercise at the same absolute intensity (SL-50 = 5.03 mg·kg-1·min-1) but was lower at the same relative intensity (SL-65 = 6.22 mg· kg-1·min-1, P < 0.01). There were no differences, however, when glucose R(d) was corrected for energy expended (kcal/min) during exercise. Respiratory exchange ratios followed the same pattern, except Carbohydrate oxidation remained lower (-23.2%, P < 0.01) at HA than at SL when corrected for energy expended. In women, unlike in men, carbohydrate utilization decreased at HA. Relative abundance of estrogen and progesterone in women may partially explain the sex differences in fuel utilization at HA, but subtle differences between menstrual cycle phases at SL had no physiologically relevant effects.

Original languageEnglish
Pages (from-to)246-256
Number of pages11
JournalJournal of Applied Physiology
Volume88
Issue number1
StatePublished - 1 Jan 2000

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Keywords

  • Gender differences
  • Glucose flux
  • Hypobaric hypoxia
  • Menstrual cycle
  • Ovarian hormones
  • Stable isotope
  • Substrate utilization

Cite this

Braun, B., Mawson, J. T., Muza, S. R., Dominick, S. B., Brooks, G. A., Horning, M. A., Rock, P. B., Moore, L. G., Mazzeo, R. S., Ezeji-Okoye, S. C., & Butterfield, G. E. (2000). Women at altitude: Carbohydrate utilization during exercise at 4,300 m. Journal of Applied Physiology, 88(1), 246-256.