Key result
The HRR-GET model yielded more accurate 6-minute oxygen uptake estimates during heavy exercise (differences of -0.55 to 0.17 L) compared to the HRR-VO2R model (overestimates of 1.3 to 2.0 L).
Why the study?
Does the HRR-GET model improve the precision of heart rate-derived VO2 estimates during heavy exercise compared to the HRR-VO2R model?
Does the HRR-GET model improve the precision of heart rate-derived VO2 estimates during heavy exercise compared to the HRR-VO2R model?
Adjusting for the gas exchange threshold significantly improves the accuracy of heart rate-derived oxygen uptake estimates during heavy exercise compared to traditional models.
HRR-GET may refine heart rate-based VO2 estimates in heavy exercise; hypothesis-generating and should not yet change practice.
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.
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Pettitt et al. (2008) studied this question. HRR-GET model vs. HRR-VO2R model was evaluated on 6 min LO2 difference (actual VO2 compared with estimates). The HRR-GET model yielded more accurate 6-minute oxygen uptake estimates during heavy exercise (differences of -0.55 to 0.17 L) compared to the HRR-VO2R model (overestimates of 1.3 to 2.0 L).
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