title: Duration of "Phase I" VO2p: a comparison of methods used in its estimation and the effects of varying moderate-intensity work rate.
abstract: The present study was designed to investigate whether absolute work rate (WR) affects Phase I pulmonary oxygen uptake (Vo(2)(p)) duration during moderate-intensity (Mod) exercise and to compare two methods for estimating Phase I Vo(2)(p) duration (P(I-Dur)). Fourteen males (24 ± 5 yr) each completed 4-8 repetitions of Mod transitions from 20 W to 50, 70, 90, 110, and 130 W. P(I-Dur) was identified by 1) a marked decrease in both respiratory exchange ratio and end-tidal partial pressure of O(2) following exercise onset [i.e., visual inspection of three independent reviewers, and the average (Avg) of the two most similar values]; or 2) the intersection (time delay, TD) of the first and second components in a biexponential nonlinear regression of the entire Vo(2)(p) response from exercise onset. P(I-Dur) did not differ among WRs (P > 0.05), regardless of the estimation method used. No differences were detected between Avg and TD (time in s) at any of the five WRs (50 W, 21 ± 6 vs. 23 ± 10 s; 70 W, 23 ± 9 vs. 23 ± 7 s; 90 W, 24 ± 3 vs. 22 ± 5 s; 110 W, 23 ± 6 vs. 22 ± 6 s; 130 W, 21 ± 6 vs. 21 ± 7 s; P > 0.05 for Avg and TD, respectively). Broad limits of agreement within Bland-Altman plots revealed relatively weak agreement among reviewers for individual estimation of P(I-Dur). A nonsignificant correlation coefficient (r = 0.13) and broad limits of agreement suggest disparity between individual Avg and TD estimates of P(I-Dur). The present data do not support a role for Mod WR in determining P(I-Dur) per se. Furthermore, this study illustrated a poor agreement of P(I-Dur) estimates derived from two different, but accepted methods.
authors.affiliation: Canadian Centre for Activity and Aging, The Univ. of Western Ontario, London, Ontario, Canada.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Spencer
authors.forename: Braden M R
authors.initials: BM
authors.lastname: Gravelle
authors.forename: Juan M
authors.initials: JM
authors.lastname: Murias
authors.forename: Livio
authors.initials: L
authors.lastname: Zerbini
authors.forename: Silvia
authors.initials: S
authors.lastname: Pogliaghi
authors.forename: Donald H
authors.initials: DH
authors.lastname: Paterson
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D010100:Oxygen