Influence of pedalling rate on oxygen consumption during eccentric exercise

Abstract

Dynamic eccentric exercise is a recent approach in terms of rehabilitation programs. These training programs are generally set on a specific workload based on a percentage of their maximal oxygen consumption (V’O2). Guidelines regarding pedaling rate can differ depending on the type of eccentric ergometer. For instance, our goal was to evaluate if these pedaling rate variations could influence (for a set work load) the level of V’O2. The hypothesis is that V’O2 will increase at a lower pedaling rate. Our goal is to evaluate the influence of pedaling rate for a set workload on oxygen consumption. We measured V’O2 of 15 healthy subjects during eccentric exercise (CPP no. AU1186) at three different amounts of work load (80-200-320 W) and two pedalling rates (50 and 80 rotations per minute [RPM]). The order was predetermined by randomization. Regarding the vastus lateralis, we recorded both the electrical activity by surface EMG and the level of tissue deoxygenation by NIRs. The data was analyzed as relative values and for each subject from the difference measured between 50 and 80 RPM. For a workload set at 200 and 320 W, V’O2 is significantly higher (P < 0.05) at 50RPM, + 94 mL.min-1 (Sd ± 139) and + 160 mL.min-1 (Sd ± 169) respectively. In addition, at 320 W, Vastus Lateralis EMG activity (quantified by root mean square) and deoxygenation level are significantly higher at 50 RPM (P < 0.05). Pedaling rate influences oxygen consumption during eccentric exercise. Lower values of V’O2 at 80 RPM vs. 50 RPM are probably due to a greater number of detachments of actin-myosin cross bridges, non ATP-dependent. A higher pedaling rate implicates a higher cycle of contraction rate and thus a higher rate of such detachments. During eccentric exercise at a set workload, pedaling rate must be taken into consideration and controlled.