At fixed power outputs, oxygen consumption is greater during arm ergometry than during leg ergometry. Researchers have speculated that during arm ergometer exercise, additional musculature is recruited to stabilize the torso. Energy required by these muscles would not contribute to power output. This is one hypothesis to explain why at a fixed power output, oxygen consumption is greater during arm ergometry than during leg ergometry. The purpose of this study was to assess the validity of this hypothesis. Nineteen apparently healthy males between the ages of 19 and 29 years volunteered to participate in this study. Subjects reported to the Human Performance Laboratory for three sessions. During the first session, subjects completed a maximal arm ergometer stress test on a Monark Rehab Trainer (Model 881E). The exercise protocol required the subject's seat height to be adjusted so that the axis of the arm ergometer was level with the subject's xiphoid process. Subjects were also positioned so that during the down stroke, the arm was at near full extension. During sessions two and three, subjects performed ten minutes of submaximal arm ergometer exercise at 65% of their maximal workrate. During one of the tests, subjects exercised with a chest plate designed to stabilize the torso and limit shoulder movement. An investigator sat directly behind the exercising subject to ensure that the torso was stabilized. During the other test, subjects performed arm ergometry without torso stabilization. Oxygen consumption was assessed with a SensorMedics 2900c Metabolic Cart. A paired sample t-test was used to test for significant differences for mean oxygen consumption values between arm ergometer exercise with the torso stabilized or un-stabilized. There were no significant differences (t=.03, p > .05) between arm exercise oxygen consumption when the torso was stabilized (1471.5+280.2 ml.min-1) and when the torso was not stabilized (1472.4+310.2 ml.min-1). Results of this study indicate that the recruitment of muscles required to stabilize the torso do not appear to explain the greater oxygen consumption during arm ergometry compared to leg ergometry when work is performed at equivalent power outputs.