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Indexed/Abstracted in: Chemical Abstracts, CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
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EXERCISE PHYSIOLOGY AND BIOMECHANICS
Hill D. W., Stevens E. C.
Department of Kinesiology, Health Promotion, and Recreation University of North Texas, Denton, TX, USA
Aim. V.O2peak can be achieved over the range of intensities that define the severe intensity domain. The purpose of this study was to help characterize the V.O2 response during constant-load exercise in this domain.
Methods. Twelve participants performed cycle ergometer tests at 267±52 W, 238±45 W, and 216±37 W, which were individually selected to elicit V.O2peak and to cause fatigue in ~3 min, ~5 min, and ~7 min, respectively.
Results. Times to fatigue were 201±16 s, 301±20 s, and 448±51 s, respectively. V.O2 responded faster at higher work rates, with V.O2peak reached after 154±25 s, 193±35 s, and 206±24 s, respectively. Extrapolation of the times to reach V.O2peak revealed that 300 W was the highest power, and 151 s was the shortest time, for which V.O2peak could be elicited. TheV.O2 response was described using a three-component model. Exercise intensity did not affect the speed of the primary response, with time constants of 22±3 s, 23±4 s, and 23±4 s, respectively. However, the size of the primary phase was greater at higher intensities, with amplitudes of 1 798±200 ml.min-1, 1 739±267 ml.min-1, and 1 677±254 ml.min-1, respectively. The amplitude of the slow component was correspondingly smaller at higher intensities. Extrapolation of the slow component amplitudes revealed that 299 W was the highest intensity, and 152-153 s was the shortest time, for which a slow component would be engendered.
Conclusion. V.O2peak is attained faster at higher intensities because the amplitude of the primary response is greater, not because the response is faster. There is a slow component to the V.O2 response at all intensities within the severe domain, but not at higher intensities, in the extreme domain, where fatigue occurs before V.O2peak can be elicited.