title: Effects of prior heavy-intensity exercise on pulmonary O2 uptake and muscle deoxygenation kinetics in young and older adult humans.
abstract: Pulmonary O2 uptake (VO2p) and muscle deoxygenation kinetics were examined during moderate-intensity cycling (80% lactate threshold) without warm-up and after heavy-intensity warm-up exercise in young (n = 6; 25 +/- 3 yr) and older (n = 5; 68 +/- 3 yr) adults. We hypothesized that heavy warm-up would speed VO2p kinetics in older adults consequent to an improved intramuscular oxygenation. Subjects performed step transitions (n = 4; 6 min) from 20 W to moderate-intensity exercise preceded by either no warm-up or heavy-intensity warm-up (6 min). VO2p was measured breath by breath. Oxy-, deoxy-(HHb), and total hemoglobin and myoglobin (Hb(tot)) of the vastus lateralis muscle were measured continuously by near-infrared spectroscopy (NIRS). VO2p (phase 2; tau) and HHb data were fit with a monoexponential model. After heavy-intensity warm-up, oxyhemoglobin (older subjects: 13 +/- 9 microM; young subjects: 9 +/- 8 microM) and Hb(tot) (older subjects: 12 +/- 8 microM; young subjects: 14 +/- 10 microM) were elevated (P < 0.05) relative to the no warm-up pretransition baseline. In older adults, tauVO2p adapted at a faster rate (P < 0.05) after heavy warm-up (30 +/- 7 s) than no warm-up (38 +/- 5 s), whereas in young subjects, tauVO2p was similar in no warm-up (26 +/- 7 s) and heavy warm-up (25 +/- 5 s). HHb adapted at a similar rate in older and young adults after no warm-up; however, in older adults after heavy warm-up, the adaptation of HHb was slower (P < 0.01) compared with young and no warm-up. These data suggest that, in older adults, VO2p kinetics may be limited by a slow adaptation of muscle blood flow and O2 delivery.
authors.affiliation: Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada N6A 3K7.
authors.forename: Darren S
authors.initials: DS
authors.lastname: DeLorey
authors.forename: John M
authors.initials: JM
authors.lastname: Kowalchuk
authors.forename: Donald H
authors.initials: DH
authors.lastname: Paterson
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*
chemical_list: D006454:Hemoglobins; D010100:Oxygen