Physiological Responses at the Critical Heart Rate During Treadmill Running

Authors

Haley Bergstrom, University of Nebraska-LincolnFollow

Date of this Version

5-2014

Citation

Bergstrom, H.C. Physiological responses at the critical heart rate during treadmill running. PhD diss. University of Nebraska-Lincoln, 2014.

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Human Sciences, Under the Supervision of Professor Terry J. Housh. Lincoln, Nebraska: May, 2014

Copyright (c) 2014 Haley C. Bergstrom

Abstract

The purposes of this study were to: 1) determine if the critical heart rate (CHR) model for cycle ergometry can be applied to treadmill running; and 2) examine the times to exhaustion (T_lim) as well as the VO₂, ratings of perceived exertion (RPE), electromyographic amplitude (EMG AMP) and mean power frequency (MPF) responses during constant heart rate (HR) runs at CHR-5 b·min^-1 (CHR-5), CHR, and CHR+5 b·min^-1 (CHR+5). Thirteen runners performed an incremental treadmill test to exhaustion. On separate days, 4 constant velocity runs to exhaustion were performed. The total number of heart beats (HB_lim) for each velocity was calculated as the product of the average 5 s HR and T_lim. The CHR was the slope coefficient of the HB_lim versus T_lim relationship. The physiological responses were recorded during the constant HR runs. Polynomial regression analyses were used to examine the patterns of responses for all. The HB_lim versus T_lim relationship (r² = 0.995 – 1.000) was described by the linear equation: HB_lim = a + CHR(T_lim). The CHR-5 (mean ± SD = 171 ± 8 b·min^-1, 88 ± 3% HR_peak), CHR (175 ± 8 b·min^-1, 91 ± 3% HR_peak), and CHR+5 (178 ± 6 b·min^-1, 94 ± 3% HR_peak) were maintained for 56.97 ± 1.23, 48.37 ± 11.04, and 20.11 ± 16.08 min, respectively. There was no change in HR, quadratic decreases in velocity and VO₂, and quadratic or linear increase in RPE during continuous runs at a constant HR. At CHR-5, EMG AMP decreased and EMG MPF increased. There was an increase in EMG AMP and no change in EMG MPF at CHR, while there was no change in EMG AMP and EMG MPF decreased at CHR+5. These findings indicated the CHR model for cycle ergometry was applicable to treadmill running, and, on average, HR values that were less than or equal to the CHR, represented sustainable (30 to 60 min) intensities, while CHR+5 did not.

Adviser: Terry J. Housh