title: Oxygen uptake kinetics in endurance-trained and untrained postmenopausal women.
abstract: The rate of adjustment for pulmonary oxygen uptake (τV̇O(2p)) is slower in untrained and in older adults. Near-infrared spectroscopy (NIRS) has shed light on potential mechanisms underlying this in young men and women and in older men; however, there is no such data available in older women. The purpose of this study was to gain a better understanding of the mechanisms of slower τV̇O(2p) in older women who were either endurance-trained or untrained. Endurance-trained (n = 10; age, 62.6 ± 1.0 years) and untrained (n = 9; age, 69.1 ± 2.2 years) older women attended 2 maximal and 2 submaximal (90% of ventilatory threshold) exercise sessions. Oxygen uptake (V̇O(2)) was measured breath by breath, using a mass spectrometer, and changes in deoxygenated hemoglobin concentration of the vastus lateralis ([HHb]) were measured using NIRS. Heart rate was measured continuously with a 3-lead electrocardiogram. τV̇O(2p) was faster in trained (35.1 ± 5.5 s) than in untrained (57.0 ± 8.1 s) women. The normalized [HHb] to V̇O(2) ratio, an indicator of muscle O(2) delivery to O(2) utilization, indicated a smaller overshoot in trained (1.09 ± 0.1) than in untrained (1.39 ± 0.1) women. Heart rate data indicated a faster adjustment of heart rate in trained (33.0 ± 13.0) than in untrained (68.7 ± 14.1) women. The pairing of V̇O(2p) data with NIRS-derived [HHb] data indicates that endurance-trained older women likely have better matching of O(2) delivery to O(2) utilization than older untrained women during moderate-intensity exercise, leading to a more rapid adjustment of V̇O(2p).
authors: School of Recreation Management and Kinesiology, Acadia University, 550 Main St, Wolfville, NS B4P 2R6, Canada. shilpa.dogra@acadiau.ca
authors: Shilpa
authors: S
authors: Dogra
authors: Matthew D
authors: MD
authors: Spencer
authors: Juan M
authors: JM
authors: Murias
authors: Donald H
authors: DH
authors: Paterson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D017698:Postmenopause / Q000502:physiology*; D013997:Time Factors