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

Purpose: This study examined the power output adjustments and subsequent shifts in metabolic (V̇O) demands as well as minute ventilation ( ), respiratory rate (RR), and rating of perceived exertion (RPE) responses during vigorous intensity (77-95% HR) heart rate (HR)-clamp cycle ergometry.

Methods: Fifteen males (mean ± SD age = 25.9 ± 4.4 years) performed a graded exercise test to exhaustion to determine peak parameters and three, randomly ordered, HR-clamp trials to exhaustion, up to 60 min, at the lower (HR = 77% HR), middle (HR = 86% HR), and higher (HR = 95% HR) end of the vigorous intensity range. Time course of changes were examined.

Results: The times to exhaustion (T) for the HR, HR, and HR trials were 56.05 ± 10.09, 44.22 ± 19.00, and 9.74 ± 7.54 min, 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 HR than HR, and HR and HR were lower than HR. The mean (HR = 56.7 ± 3.8, HR = 68.1 ± 4.3, and HR = 90.5 ± 3.3% ) responses fell below the recommended range for vigorous exercise at 10%T for HR, and at 90%T for HR, but remained above the recommended V̇O range for vigorous exercise until 70% of T for HR.

Conclusions: Only the HR trial met the current guidelines of a vigorous intensity sustained for at least 20 min. This study indicated that HR-clamp exercise cannot be consistently used to prescribe a desired metabolic stimulus for exercise performed in a single session.