Several investigators have demonstrated that chronic eccentric leg cycling is an effective method for improving lower body neuromuscular function (e.g., quadriceps muscle size, strength, and mobility) in a variety of patient and athletic populations. To date, there are no reports of using eccentricarm cycling (ECarm) as an exercise modality, probably in large part because of the lack of commercially available ECarm ergometers. Purpose: Our purposes for conducting this study were to 1) describe the design and construction of an ECarm ergometer and 2) compare ECarm to traditional concentric arm cycling (CCarm). Methods: All of the parts of a Monark 891E cycle ergometer (Monark Exercise AB, Vansbro, Sweden) were removed, leaving the frame and flywheel. An electric motor (2.2 kW) was connected to the flywheel via a pulley and a belt. Motor speed and pedaling rate were controlled by a variable frequency drive. A power meter quantified power and pedaling rate, and provided feedback to the individual. Eight individuals performed 3-min ECarm and CCarm trials at 40, 80, and 120 W (60 rpm) while V̇O₂ was measured. Results: The ECarm ergometer was simple to use, was adjustable, provided feedback on power output to the user, and allowed for a range of eccentric powers. V̇O₂ during ECarm was substantially lower compared with CCarm (P < 0.001). At similar V̇O₂ (0.97 ± 0.18 vs 0.91 ± 0.09 L•min, for ECarm and CCarm, respectively, P = 0.26), power absorbed during ECarm was approximately threefold greater than that produced during CCarm (118 ± 1 vs 40 ± 1 W, P < 0.001). Conclusion: This novel ECarm ergometer can be used to perform repetitive, high-force, multijoint, eccentric actions with the upper body at a low level of metabolic demand and may allow researchers and clinicians to use ECarm as a training and rehabilitation modality. © 2012 by the American College of Sports Medicine.