The impact of contractile mode and work volume on the prediction of cortisol concentrations from flywheel-based resistive exercise workouts

To assess cortisol concentrations (CC) from flywheel ergometer resistive exercise, subjects performed three different leg press workouts on the device. Comprised of ten-repetition sets, the workouts entailed 1): a three-set protocol composed of concentric and eccentric actions (CE3), as well as concentric-only paradigms comprised of 2): three (CO3) and 3): six (CO6) sets. Venous blood draws, collected before workouts and at one and 30 minutes post-exercise, measured CC. ANOVA yielded CC results similar to studies that employed standard resistive exercise equipment. However multivariate regression revealed body mass, peak angular velocity and average power were strong predictors of post-exercise CC. Separate multivariate analyses of the CE3 and pooled concentric-only (CO3 and CO6 combined) data show differences in level of explained (r²) variance, which was likely due to the ergometer's operation. Constant torque exertion throughout the CE3 bout meant performance was continual only for that workout and evoked more explained variance versus the concentric-only trials. The current ergometer was originally intended for use aboard manned spacecraft and is a prototype to newer flywheel-based resistive exercise devices. Future research should assess responses to workouts in a bed rest model to determine which protocol best abates CC to further aid future in-flight exercise.