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.
1Respiratory, Cardiocirculatory and Exercise Functional Explorations Department, Civil Hospital, Strasbourg, FRANCE; and Physiology Department, Faculty of Medicine, Strasbourg, FRANCE; and 2LIGE Laboratory, UFR of Fundamental and Applied Sciences, University of Evry Val d’Essonne, FRANCE
Address for correspondence: Stéphane P. Dufour, Service des Explorations Fonctionnelles Respiratoires, Cardiovasculaires et de l’Exercice, Hôpital Civil, 1 Place de l’Hôpital, BP 426, F-67091 Strasbourg Cedex, France; E-mail: firstname.lastname@example.org.
Submitted for publication March 2004.
Accepted for publication July 2004.
We gratefully thank all the subjects for their voluntary participation and Jean-Pierre Speich for the conception and development of the ECC ergometer as well as for his constant technical assistance. We are also indebted to Professor Jean Lonsdorfer and the entire staff of the Service des Explorations Fonctionnelles Respiratoires, Cardiovasculaires et de l’Exercice for their daily support and material contributions as well as to Prof. Meyer for his statistical advices.
This study was supported by the Département de Recherche Clinique of the Strasbourg University Hospital.