title: Sex differences in endurance capacity and metabolic response to prolonged, heavy exercise.
abstract: In order to test for possible sex differences in endurance capacity, groups of young, physically active women (n = 6) and men (n = 7) performed bicycle ergometer exercise at 80% and 90% of their maximal oxygen uptakes (VO2 max). The groups were matched for age and physical activity habits. At 80% VO2 max the women performed significantly longer (P less than 0.05), 53.8 +/- 12.7 min vs 36.8 +/- 12.2 min, respectively (means +/- SD). Mid-exercise and terminal respiratory exchange ratio (R) values were significantly lower in women, suggesting a later occurrence of muscle glycogen depletion as a factor in their enhanced endurance. At 90% VO2 max the endurance times were similar for men and women, 21.2 +/- 10.3 min and 22.0 +/- 5.0 min, respectively. The blood lactate levels reached in these experiments were only marginally lower (mean differences 1.5 to 2 mmol X l-1) than those obtained at VO2 max, suggesting high lactate levels as a factor in exhaustion. The changes in body weight during the 80% experiments and the degree of hemoconcentration were not significantly different between men and women.
mesh_terms: D000328:Adult; D004734:Energy Metabolism; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000502:physiology; D006801:Humans; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D007866:Leg; D008297:Male; D009132:Muscles / Q000378:metabolism; D010101:Oxygen Consumption; D010807:Physical Endurance; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012737:Sex Factors
chemical_list: D007773:Lactates; D019344:Lactic Acid