title: O2 uptake kinetics and the O2 deficit as related to exercise intensity and blood lactate.
abstract: The dynamic responses of O2 uptake (VO2) to a range of constant power output levels were related to exercise intensity [as percent maximal VO2 and as below vs. above lactic acid threshold (LAT)] and to the associated end-exercise lactate in three groups of subjects: group I, untrained subjects performing leg cycle ergometer exercise; group II, the same subjects performing arm cycle exercise; and group III, trained cyclists performing leg cycle ergometer exercise. Responses were described by a double-exponential equation, with each component having an independent time delay, which reduced to a monoexponential description for moderate (below-LAT) exercise. When a second exponential component to the VO2 response was present, it did not become evident until approximately 80-100 s into exercise. An overall time constant (tau T, determined as O2 deficit for the total response divided by net end-exercise VO2) and a primary time constant (tau P, determined from the O2 deficit and the amplitude for the early primary VO2 response) were compared. The tau T rose with power output and end-exercise lactate levels, but tau P was virtually invariant, even at high end-exercise lactate levels. Moreover the gain of the primary exponential component (as delta VO2/delta W) was constant across power outputs and blood lactate levels, suggesting that the primary VO2 response reflects a linear system, even at higher power outputs. These results suggest that elevated end-exercise lactate is not associated with any discernible slowing of the primary rise in VO2.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, Harbor-UCLA Medical Center, Torrance 90509.
authors.forename: T J
authors.initials: TJ
authors.lastname: Barstow
authors.forename: R
authors.initials: R
authors.lastname: Casaburi
authors.forename: K
authors.initials: K
authors.lastname: Wasserman
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001132:Arm / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006801:Humans; D007700:Kinetics; D007773:Lactates / Q000097:blood*; D007866:Leg / Q000502:physiology; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology
chemical_list: D007773:Lactates