title: Adjustment for gas exchange threshold enhances precision of heart rate-derived VO2 estimates during heavy exercise.
abstract: Overestimates of oxygen uptake (VO2) are derived from the heart rate reserve-VO2 reserve (HRR-VO2R) model. We tested the hypothesis that adjusting for differences above and below gas exchange threshold (HRR-GET model) would tighten the precision of HR-derived VO2 estimates during heavy exercise. Seven men and 7 women of various VO2 max levels, on 2 separate days, cycled for 6 min at intensities equal to power at GET, 15% the difference between GET and VO2 max (15% above), and at 30% above GET. A second bout at 15% above GET (15% above (bout 2)) after 3 min of recovery was performed to assess estimates during interval training. Actual VO2 was compared with estimates derived from the HRR-VO2R and the HRR-GET. VO2 values were summed over the 6 min duration of data collection (6 min LO2) and compared with Bland-Altman plots. HRR-VO2R yielded 6 min LO2 (+/-2 SD) overestimates of 2.0 (+/-2.5), 1.9 (+/-2.7), and 1.3 (+/-3.3) for GET, 15% over, and 30% over, respectively, whereas corresponding 6 min LO2 difference values for the HRR-GET model were -0.42 (+/-1.6), -0.23 (+/-1.1), and -0.55 (+/-1.8), respectively. For 15% above (bout 2), the 6 min LO2 difference for HRR-VO2R was 1.8 (+/-2.9), whereas the difference for HRR-GET was 0.17 (+/-1.4). The 6 min LO2 values relative to the subjects' VO2 max did not vary (r=0.05 to 0.36); therefore, fitness level did not affect estimates. Sex did not affect accuracy of either estimate model (sex X estimate model interaction, p>0.95). We observed accurate estimates from the HRR-GET model during heavy exercise.
authors.affiliation: California State University, Fresno, 5275 North Campus Drive M/S SG28, Fresno, CA 93740, USA. rpettitt@csufresno.edu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Pettitt
authors.forename: J David
authors.initials: JD
authors.lastname: Symons
authors.forename: Julie E
authors.initials: JE
authors.lastname: Taylor
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Eisenman
authors.forename: Andrea T
authors.initials: AT
authors.lastname: White
mesh_terms: D000328:Adult; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*