Vigorous intensity heart rate-clamp exercise does not elicit recommended oxygen consumption rates.

Abstract

This study examined the power output adjustments and subsequent shifts in metabolic (V̇O2) demands as well as minute ventilation ( ), respiratory rate (RR), and rating of perceived exertion (RPE) responses during vigorous intensity (77-95% HRpeak) heart rate (HR)-clamp cycle ergometry. Fifteen males (mean ± SD age = 25.9 ± 4.4years) performed a graded exercise test to exhaustion to determine peak parameters and three, randomly ordered, HR-clamp trials to exhaustion, up to 60min, at the lower (HRL = 77% HRpeak), middle (HRM = 86% HRpeak), and higher (HRH = 95% HRpeak) end of the vigorous intensity range. Time course of changes were examined. The times to exhaustion (Tlim) for the HRL, HRM, and HRH trials were 56.05 ± 10.09, 44.22 ± 19.00, and 9.74 ± 7.54min, respectively. There were significant decreases in power output, , and across time for each trial, but no changes in RR, and increases in RPE (p < 0.05). Responses were intensity specific for all variables such that mean values were lower for HRL than HRM, and HRL and HRM were lower than HRH. The mean (HRL = 56.7 ± 3.8, HRM = 68.1 ± 4.3, and HRH = 90.5 ± 3.3% ) responses fell below the recommended range for vigorous exercise at 10%Tlim for HRL, and at 90%Tlim for HRM, but remained above the recommended V̇O2 range for vigorous exercise until 70% of Tlim for HRH. Only the HRM trial met the current guidelines of a vigorous intensity sustained for at least 20min. This study indicated that HR-clamp exercise cannot be consistently used to prescribe a desired metabolic stimulus for exercise performed in a single session.