title: Women at altitude: carbohydrate utilization during exercise at 4,300 m.
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 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 < 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.
authors.affiliation: 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, USA.
authors.forename: B
authors.initials: B
authors.lastname: Braun
authors.forename: J T
authors.initials: JT
authors.lastname: Mawson
authors.forename: S R
authors.initials: SR
authors.lastname: Muza
authors.forename: S B
authors.initials: SB
authors.lastname: Dominick
authors.forename: G A
authors.initials: GA
authors.lastname: Brooks
authors.forename: M A
authors.initials: MA
authors.lastname: Horning
authors.forename: P B
authors.initials: PB
authors.lastname: Rock
authors.forename: L G
authors.initials: LG
authors.lastname: Moore
authors.forename: R S
authors.initials: RS
authors.lastname: Mazzeo
authors.forename: S C
authors.initials: SC
authors.lastname: Ezeji-Okoye
authors.forename: G E
authors.initials: GE
authors.lastname: Butterfield
mesh_terms: D000328:Adult; D000531:Altitude; D001481:Basal Metabolism; D001786:Blood Glucose / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002395:Catecholamines / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008597:Menstrual Cycle / Q000097:blood / Q000502:physiology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D012727:Sex Characteristics
chemical_list: D001786:Blood Glucose; D002395:Catecholamines; D007328:Insulin; D019344:Lactic Acid; D006854:Hydrocortisone