Author ORCID Identifier
Year of Publication
Master of Science (MS)
Kinesiology and Health Promotion
Dr. Haley C. Bergstrom
Exercise prescription to improve cardiorespiratory endurance (CE) is often based on percentages of the reserve or maximum heart rate (HRpeak) or oxygen consumption rate (V̇O2peak)that reflect vigorous intensities (77-95% HRpeak, 64-90% V̇O2peak). These intensities elicit a rating of perceived exertion [RPE] response between 14-17 on the 6-20 Borg Scale. It is recommended that exercise within these ranges be sustained for 20-60min per session. The purposes of this study were to: 1) Determine the metabolic (V̇O2) and perceptual (RPE) responses as well as the sustainability of exercise (time to exhaustion [Tlim]) anchored to heart rates (HR) at the lower (HRL= 77% peak heart rate [HRpeak]), middle (HRM=86% HRpeak), and higher (HRH= 95%HRpeak) ends of the range recommended for vigorous exercise; 2) determine if the V̇O2 and RPE response remain within the recommended ranges for vigorous exercise throughout the trials at HRL, HRM, HRH by examining the time course of changes and patterns of responses for these variables as well as power output (PO), respiratory exchange ratio (RER), minute ventilation (E), and respiratory rate (RR) responses; and 3) determine the time spent in the severe (> respiratory compensation point [RCP]), heavy (< RCP, > ventilatory threshold [VT]), and moderate (< VT) intensity domains for the composite and on a participant-by-participant basis during each of the constant HR trials. Twelve, moderately trained, participants performed a graded exercise test to exhaustion on a calibrated cycle ergometer to determine the peak responses for HR (HRpeak), V̇O2 (V̇O2peak), RPE, RER, V̇E, RR,and peak power output as well as the VT and RCP. On separate days, constant HR trials were performed at HRL, HRM, and HRH, in a randomized order. The O2, RER, E, RR,power output (PO), RPE, and Tlim were examined during the randomly ordered continuous trials to exhaustion or up to 60 min. The HRL (143±8 beats×min-1 [b×min-1]), the HRM (159±8 b×min-1), and the HRH (176±9 b×min-1) were maintained for 53.42±13.19, 46.75±18.79, and 27.05±18.00 min, respectively, not including the time to reach the desired HR. A one-way repeated measures ANOVA (F=26.196, p ≤ 0.001, ηp2=0.704) and post-hoc, t-tests with a Bonferroni corrected alpha (p < 0.017) indicated the Tlim at HRL and HRM were both significantly longer than Tlim at HRH (p < 0.001), but Tlim for HRM and HRL were not different. Responses across time were examined with 3(Intensity: HRL, HRM, and HRH) x 10(Time: 10-100%Tlim) repeated measures ANOVAs and post-hoc analysis. The O2, collapsed across intensity, was significantly lower than the initial value (10%Tlim) from 20-100% Tlim (p < 0.001). The RPE, collapsed across intensity, was significantly higher than the initial value (10%) from 30-100% of Tlim(p=0.0001 to 0.0019). For HRL trial, the composite (average of all subjects across time) V̇O2 (53.9±7.1% V̇O2peak) and RPE (RPE of 12±3) responses were lower than the recommended range during the trials. For the HRM trial, the average V̇O2 (64±7% V̇O2peak) and RPE (RPE of 14±2) responses were within the recommended range for 40% (~19 min) and 70% of Tlim, respectively. For HRH trial, the average V̇O2 (80±8% V̇O2peak) and RPE (RPE of 17±1) responses were within the recommended range for the entire trial. On a participant-by-participant basis, the HRH was the only intensity where approximately half of the participants were within the recommended V̇O2 (58% of participants) or RPE (67% of participants) ranges for 20 min. An additional 3(Intensity: HRL, HRM, and HRH) x 10(Time: 10-100%Tlim) repeated measures ANOVAs and post-hoc analysis were performed for PO, RER, V̇E, and RR. The PO, collapsed across intensity, was significantly lower than the initial value (10%) from 20-100% of Tlim (p=0.0002 to 0.0014) for all comparisons. The RER at HRL, HRM, and HRL, were significantly lower than the initial value (10%) from 20-100% of Tlim (p=0.0001 to 0.0006). The RER for HRH was greater than HRL and HRM at most time points, however, there were no differences in RER between HRL and HRM. The V̇E, collapsed across intensity, was significantly lower than the initial value (10%) from 20-100% of Tlim (p=0.0001 to 0.0002) and the RR, collapsed across intensity, was significantly higher than the initial value (10%) from 70-90% of Tlim (p=0.0013 to 0.0019). The repeated measures ANOVA examining time in each intensity domain indicated there was a 2-way interaction (F =25.588, p ≤ 0.001, ηp2=0.699). The post-hoc t-tests indicated that at HRL, the participants spent significantly more in the moderate domain than the heavy (p ≤ 0.001) and severe (p ≤ 0.001). There was no significant difference in the time spent within the heavy and severe domains (p=0.053). At HRM, more time was spent in the moderate than the heavy (p=0.002) and severe (p ≤ 0.001) domains and there was more time spent within the heavy than the severe (p=0.010). Finally, at HRHthere were no significant differences between the time spent in the moderate compared to the heavy domain (p=0.318), severe (p=0.017), or between the heavy and severe (p=0.036). There were intensity specific metabolic demands that demonstrated the HRH elicited the highest metabolic cost and RER relative to HRM and HRL. The decreases in V̇O2 tracked PO and V̇E followed a similar pattern for each trial. The RPE increased during each HR trial and RR tracked this response. The increases in RPE may be attributed to an increase in the RR and feedback from mechanical and metabo-sensitive group III/IV afferent neurons. The O2 and RPE findings indicated that exercise anchored at HRL and HRM may not provide an intensity that meets the current guidelines for improving CE fitness. While HRH may be at a sufficient intensity to elicit the desired metabolic responses on average, it may not be for all participants. Thus, these data indicated that HRpeak should not be used to prescribe a desired metabolic intensity.
Digital Object Identifier (DOI)
Gustave, Djadmann, "RESPONSES TO EXERCISE ANCHORED TO VIGOROUS INTENSITY HEART RATES" (2023). Theses and Dissertations--Kinesiology and Health Promotion. 97.