%Heart Rate Reserve Is Better Related to %VO2max Than to %VO2 reserve

0063 The intensity guidelines for prescribing aerobic exercise were recently revised by ACSM to use %VO2reserve (%VO2R) rather than %VO2max. PURPOSE: The current study investigated the relationship of %VO2max and %VO2R with %Heart Rate Reserve (%HRR) in 630 initially sedentary individuals (ages 17 to 65). METHODS: Each participant completed 2 graded cycle tests to exhaustion before and after 20 weeks of training. VO2 and HR data were collected at the end of each stage. Resting HR and estimated resting VO2 (3.5 ml•kg−1•min−1) were additionally used to determine linear regressions of %HRR vs. %VO2max and %HRR vs. %VO2R. Slope and intercept were determined pre- and post-training for the total cohort and for subjects grouped by gender, race, age and baseline fitness (VO2max). RESULTS: Overall, and in all sub-groups, both pre- and post-training, the slope and intercepts were significantly different from 1.0 and 0, respectively for both %HRR vs. %VO2max and %HRR vs. %VO2R. However, the slopes and intercepts for %HRR vs. %VO2max were closer to the line of unity than were the slopes and intercepts of %HRR vs. %VO2R (p< 0.01 to 0.0001). More importantly, the calculated HR values for %HRR vs. %VO2max were closer (p<0.001) at 50% (+0.4±2.2 bpm) and 85% (+3.8 ± 3.2) than the values for %HRR vs. % VO2R at 50% (+8.2 ± 2.6 bpm) and 85% (+6.6 ± 3.4 bpm). Posttraining data differences were similar, though of smaller magnitude, with HR values at 50 and 85% VO2max more similar (p<0.01) to %HRR than were %VO2R HR values to %HRR. CONCLUSION: These results differ from those of Swain et al. who studied young adults during treadmill (n = 50) and cycle (n = 57) testing. Since %VO2R is a more difficult calculation than %VO2max and is less understood and since the differences in HR values within the normal aerobic training range were significantly closer using %VO2max, %VO2max is the better measure for prescribing exercise intensity. Supported by multiple grants from NIH/NHLBI.