Background: Astronauts are required to perform both resistance and aerobic exercise while in orbit. This study assessed the aerobic energy yield and related physiological measurements using a nongravity dependent flywheel device designed for both resistance and aerobic exercise (RAD) in space. Methods: Eight physically active men and women performed all-out rowing on the RAD. For comparison, exercise was also carried out employing a commercially available rowing ergometer (C2). Results: Peak oxygen uptake during exercise using RAD and C2 averaged 3.11 ± 0.49 and 3.18 ± 0.50 L · min-1 respectively. Similarly, peak plasma lactate concentration (9.6 vs. 11.2 mmol · L-1), heart rate (183 vs. 184 bpm), and rate of perceived exertion (15.8 vs. 16.0) were comparable across exercise using the two devices. Discussion: Collectively, the results suggest that this novel exercise modality offers cardiovascular and metabolic responses, and thus aerobic exercise stimulus that is equally effective as that evoked by established technology for indoor rowing. Given the need for physiologically sound and highly effective exercise countermeasures that features small mass and envelope, and allows for resistance and aerobic exercise in a single apparatus, we believe this novel hardware should be considered for use in space. © by the Aerospace Medical Association, Alexandria, VA.