Purpose: Despite identical oxygen uptake (V̇O2), enhanced heart rate (HR) and cardiac output (Q̇) responses have been reported in eccentric (ECC) versus concentric (CON) cycle exercise. The aim of this study was to describe the specific circulatory adjustments (HR and stroke volume (SV)) to incremental ECC cycle exercise in order to: 1) determine the HR values leading to identical V̇O2 in ECC and CON cycling; and 2) estimate the interindividual variability of this HR correspondence between the two exercise modes, with emphasis upon rehabilitation and training purposes.
Methods: Eight healthy male subjects (age, 28 ± 2 yr) participated in this study. They performed CON and ECC cycle incremental exercises (power output increases of 50 W every 3 min). Breath-by-breath gas exchange analysis and beat-by-beat thoracic impedancemetry were used to determine V̇O2 and Q̇, respectively.
Results: At the same metabolic power (V̇O2 of 1.08 ± 0.05 L·min−1 in CON vs 1.04 ± 0.06 L·min−1 in ECC), SV was not different, but HR was 17% higher in ECC (P < 0.01), leading to a 27% enhanced Q̇ (P < 0.01). Q̇ and HR net adjustments (exercise minus resting values) in ECC versus CON muscle involvement demonstrated important interindividual variability with coefficients of variation amounting to 32% and 30%, respectively.
Conclusion. In practice, if a given level of V̇O2 is to be reached, ECC HR has to be set above the CON one. Taking into account the interindividual variability of the circulatory adjustments in ECC versus CON muscle involvement, a precise HR correspondence can be established individually from the V̇O2/HR relationship obtained using ECC incremental testing, allowing prescription of accurate target HR for rehabilitation or training purposes.