Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis




Kinesiology and Health Promotion

First Advisor

Dr. Haley C. Bergstrom


The purposes of this study were to: 1) Determine if there are differences in the sustainability of exercise when anchored at critical heart rate (CHR), the VO2 associated with CHR (VO2CHR), or the power output associated with CHR (PCHR); 2) examine the patterns of responses in power output, metabolic (heart rate [HR], VO2, respiration rate [RR]), neuromuscular (electromyographic [EMG] amplitude [AMP], mean power frequency [MPF], mechanomyographic [MMG] AMP and MPF, perceptual (rating of perceived exertion [RPE]), and muscle oxygenation responses (%SmO2) during exercise anchored by HR, VO2, and power output; and 3) determine if the CHR can be used for exercise prescription based on time to exhaustion (TLim), physiological, perceptual, and neuromuscular responses. Six, moderately trained, subjects performed a graded exercise test (GXT). On separate days, 4 constant power output trials were performed in a randomized order at 85%, 90%, 95%, and 100% of the peak power output (PPO) determined from the GXT. The total number of heart beats (HBLim) for each power output was calculated as the product of the average 5-second HR and TLim for each constant power output trial. The CHR was defined as the slope of the linear regression of the HBLim versus TLim relationship. The VO2CHR was derived from the linear regression equation of the VO2 versus HR relationship from the GXT where VO2CHR was defined as the VO2 corresponding to CHR. Similarly, the PCHR was derived from the linear regression of the power output versus HR relationship from the GXT where the PCHR was defined as the power output corresponding to CHR. The physiological, perceptual, and neuromuscular responses were recorded during trials at CHR, VO2CHR, and PCHR. Polynomial regression analyses were used to examine the patterns of responses for all variables. The HBLim versus TLim (r2 = 0.9946-0.9995), the VO2 versus HR (r2 = 0.8833 – 0.9899), and the power output versus HR (r2 = 0.9600 – 0.9886) relationships were highly linear. The CHR (170 ± 9 beats×min-1, 91 ± 5% HRmax), VO2CHR (31.55 ± 7.85 mL×kg-1×min-1, 81± 10% O2peak), and PCHR (199 ± 70 Watts, 75 ± 11% PPO) were maintained for 46.28 ± 18.49, 28.93 ± 24.41, 22.60 ± 21.61 min, respectively. At CHR, there was no change in HR, quadratic decreases in VO2 (R2 = 0.976) and power output (R2 = 0.900), quadratic increases in RR (R2 = 0.590), EMG MPF (R2 = 0.986), and MMG MPF (R2 = 0.739), linear increases in RPE (r2 = 0.960), %SmO2 (r2 = 0.940), and MMG AMP (r2 = 0.921), and linear decreases in EMG AMP (r2 = 0.935). At VO2CHR, there was no change in EMG AMP, MMG AMP, and MMG MPF, quadratic decreases in power output (R2 = 0.810), quadratic increases in RPE (R2 = 0.964), linear decreases in VO2 (r2 = 0.580) (despite VO2start = 31.15 mL×kg-1×min-1 not being different from VO2end = 30.85 mL×kg-1×min-1), and linear increases in HR (r2 = 0.860, RR (r2 = 0.940), %SmO2 (r2 = 0.390), and EMG MPF (r2 = 1.000). At PCHR, there was no change in power output, and MMG AMP, quadratic decreases in EMG MPF (R2 = 0.700), quadratic increases in VO2 (R2 = 0.839), HR (R2 = 0.960), and RPE (R2 = 0.996), linear increases in RR (r2 = 0.990), and EMG AMP (r2 = 0.500), and linear decreases in %SmO2 (r2 = 0.720), and MMG MPF (r2 = 0.547). These findings indicated the CHR was more sustainable than VO2CHR and PCHR, and may provide a suitable stimulus for cardiorespiratory endurance training.

Digital Object Identifier (DOI)