title: Exercise performance and VO2 kinetics during upright and recumbent high-intensity cycling exercise.
abstract: This study investigated cycling performance and oxygen uptake V(O)₂kinetics between upright and two commonly used recumbent (R) postures, 65 degrees R and 30 degrees R. On three occasions, ten young active males performed three bouts of high-intensity constant-load (85% peak-workload achieved during a graded test) cycling in one of the three randomly assigned postures (upright, 65 degrees R or 30 degrees R). The first bout was performed to fatigue and second and third bouts were limited to 7 min. A subset of seven subjects performed a final constant-load test to failure in the supine posture. Exercise time to failure was not altered when the body inclination was lowered from the upright (13.1 +/- 4.5 min) to 65 degrees R (10.5 +/- 2.7 min) and 30 degrees R (11.5 +/- 4.6 min) postures; but it was significantly shorter in the supine posture (5.8 +/- 2.1 min) when compared with the three inclined postures. Resulting kinetic parameters from a tri-exponential analysis of breath-by-breath V(O)₂data during the first 7 min of exercise were also not different between the three inclined postures. However, inert gas rebreathing analysis of cardiac output revealed a greater cardiac output and stroke volume in both recumbent postures compared with the upright posture at 30 s into the exercise. These data suggest that increased cardiac function may counteract the reduction of hydrostatic pressure from upright approximately 25 mmHg; to 65 degrees R approximately 22 mmHg; and 30 degrees R approximately 18 mmHg such that perfusion of active muscle presumably remains largely unchanged, and also therefore, V(O)₂kinetics and performance during high-intensity cycling.
authors.affiliation: Department of Physiology, Trinity College Dublin, Dublin 2, Ireland. megana@tcd.ie
authors.forename: Mikel
authors.initials: M
authors.lastname: Egaña
authors.forename: Damien
authors.initials: D
authors.lastname: O'Riordan
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Warmington
mesh_terms: D000222:Adaptation, Physiological; D001642:Bicycling; D002302:Cardiac Output; D015444:Exercise; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D006874:Hydrostatic Pressure; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D011187:Posture; D013318:Stroke Volume; D016683:Supine Position; D055815:Young Adult
chemical_list: D010100:Oxygen
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