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

1 Aging Study Unit, Geriatric Research, Education, and Clinical Center, Veterans Affairs Health Care System, and Division of Gerontology, Endocrinology, and Metabolism, Stanford University Medical School, Palo Alto, California 93404; 2 Thermal and Mountain Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760; 3 Department of Integrative Biology, University of California, Berkeley, California 94720; 4 Womens Health Research Center, University of Colorado, Denver 80262; and 5 Department of Kinesiology and Applied Physiology, University of Colorado, Boulder, Colorado 80309 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 O 2 consumption in different menstrual cycle phases (SL-50), at 65% of peak O 2 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