BACKGROUND: To limit physiological changes incurred with space flight, exercise hardware should impart sufficient mechanical loads with minimal energy costs.
OBJECTIVE: Assess net energy costs from exercise done on flywheel-based hardware.
METHODS: Subjects (17 men, 19 women) performed the following leg press workouts in a randomized sequence: two sets of concentric-only (CO2) actions, two sets with both concentric and eccentric (CE2) activity, and four sets of concentric-only (CO4) actions. Workouts entailed 8-repetition sets with 90-second rest periods. O2 was measured before, during and after workouts to calculate net energy costs. Total work (TW) was derived from flywheel rotation rates as follows: TW = (1/2)(J)(ω 2) whereby J = rotation inertia and ω = angular velocity. TW and net energy costs were assessed with 2(gender) × 3(workout) ANOVAs with repeated measures for workout.
RESULTS: TW had significant differences by gender (men > women) and workout (CE2, CO4 > CO2). Net energy costs also yielded significant differences by gender (men > women) and workout (CO4 > CE2, CO2).
CONCLUSIONS: For the CE2 workout ∼ 50% of the TW occurred through muscle lengthening. Eccentric actions should be part of workouts done on this hardware, as they impart large mechanical loads with little net energy cost.
