title: Estimated times to exhaustion at the PWC V O2, PWC HRT, and VT.
abstract: The purpose of this study was to validate the Physical Working Capacity at the Heart Rate Threshold (PWC HRT) and Physical Working Capacity at the Oxygen Consumption Threshold (PWC V O2) tests by 1) using individual power vs. duration relationships to estimate the times to exhaustion (ETTE) at the PWC HRT and PWC V O2, and 2) comparing the power outputs and ETTE values of the PWC HRT and PWC V O2 with those of the ventilatory threshold (VT). Ten adults (mean age +/- SD = 23 +/- 1 years) performed an incremental test to exhaustion on a cycle ergometer for the determination of V O2 peak and VT. The subjects also performed four randomly ordered workbouts to exhaustion at different power outputs (ranging from 98 to 246 W) to determine the PWC V O2, PWC HRT, and power vs. duration relationship. Power curve analyses (y = ax b) were used to define the hyperbolic power vs. duration relationship for each subject and to determine the ETTE at the PWC V O2, PWC HRT, and VT. Two separate one-way repeated-measures analyses of variance indicated that there were significant differences among the fatigue thresholds (PWC V O2 > PWC HRT) and ETTE values (PWC HRT > PWC V O2): PWC V O2 (mean +/- SD = 147 +/- 43 W; ETTE = 21 +/- 3 minutes), PWCHRT (136 +/- 37 W; ETTE = 29 +/- 6 minutes), and VT (143 +/- 44 W; ETTE = 27 +/- 11 minutes). These findings were consistent with previous studies that indicated that the PWC HRT occurred at a lower power output than the PWC V O2. Furthermore, the PWC HRT was maintained for a mean of 29 minutes, whereas the PWC V O2 and VT were maintained for 21 and 27 minutes, respectively. These findings indicate that the ETTE values for the PWC V O2 and PWC HRT were substantially less than those suggested in previous studies.
authors.affiliation: Department of Nutrition and Health Sciences, Human Performance Laboratory, University of Nebraska-Lincoln, Lincoln, Nebraska, USA. mmielke@unlserve.unl.edu
authors.forename: Michelle
authors.initials: M
authors.lastname: Mielke
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Housh
authors.forename: Moh H
authors.initials: MH
authors.lastname: Malek
authors.forename: Travis W
authors.initials: TW
authors.lastname: Beck
authors.forename: C Russell
authors.initials: CR
authors.lastname: Hendrix
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Schmidt
authors.forename: Glen O
authors.initials: GO
authors.lastname: Johnson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005080:Exercise Test / Q000379:methods*; D005221:Fatigue / Q000503:physiopathology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D015203:Reproducibility of Results