by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. Copyright @ 2010 Musculoskeletal Adaptations to Training with the Advanced Resistive Exercise Device JAMES A. LOEHR 1 , STUART M. C. LEE 1 , KIRK L. ENGLISH 2 , JEAN SIBONGA 3 , SCOTT M. SMITH 4 , BARRY A. SPIERING 1 , and R. DONALD HAGAN 41 1 Wyle Integrated Science and Engineering Group, Houston, TX; 2 JES Tech, Houston, TX; 3 Universities Space Research Association, Houston, TX; and 4 NASA Johnson Space Center, Houston, TX ABSTRACT LOEHR, J. A., S. M. C. LEE, K. L. ENGLISH, J. SIBONGA, S. M. SMITH, B. A. SPIERING, and R. D. HAGAN. Musculoskeletal Adaptations to Training with the Advanced Resistive Exercise Device. Med. Sci. Sports Exerc., Vol. 43, No. 1, pp. 146–156, 2011. Resistance exercise has been used as a means to prevent the musculoskeletal losses associated with spaceflight. Therefore, the National Aeronautics and Space Administration designed the Advanced Resistive Exercise Device (ARED) to replace the initial device flown on the International Space Station. The ARED uses vacuum cylinders and inertial flywheels to simulate, in the absence of gravity, the constant mass and inertia, respectively, of free weight (FW) exercise. Purpose: To compare the musculoskeletal effects of resistance exercise training using the ARED with the effects of training with FW. Methods: Previously untrained, ambulatory subjects exercised using one of two modalities: FW (6 men and 3 women) or ARED (8 men and 3 women). Subjects performed squat, heel raise, and dead lift exercises 3 dIwk j1 for 16 wk. Squat, heel raise, and dead lift strength (one-repetition maximum; using FW and ARED), bone mineral density (via dual-energy x-ray absorptiometry), and vertical jump were assessed before, during, and after training. Muscle mass (via magnetic resonance imaging) and bone morphology (via quantitative computed tomography) were measured before and after training. Bone biomarkers and circulating hormones were measured before training and after 4, 8, and 16 wk. Results: Muscle strength, muscle volume, vertical jump height, and lumbar spine bone mineral density (via dual-energy x-ray absorptiometry and quantitative computed tomography) significantly increased (P e 0.05) in both groups. There were no significant differences between groups in any of the dependent variables at any time. Conclusions: After 16 wk of training, ARED exercise resulted in musculoskeletal effects that were not significantly different from the effects of training with FW. Because FW training mitigates bed rest–induced deconditioning, the ARED may be an effective countermeasure for spaceflight-induced deconditioning and should be validated during spaceflight. Key Words: RESISTANCE EXERCISE, SPACEFLIGHT, MUSCLE STRENGTH, BONE MINERAL DENSITY, iRED D ecreased muscle function and loss of bone strength during long-duration spaceflight may jeopardize crew health and mission success by impairing or limiting work performance or by increasing the risk of muscle injury or bone fracture. During bed rest, a spaceflight analog, high-intensity resistance exercise protects against musculoskeletal deconditioning (6,5,12,27). Therefore, the National Aeronautics and Space Administration (NASA) deployed the interim Resistive Exercise Device (iRED) in 2001 as an exercise countermeasure during long-duration stays aboard the International Space Station (ISS). Despite the availability of the iRED, results from long-duration ISS missions (Q4 months) indicate that astronauts continue to lose muscle mass, muscle strength, and bone mineral density (BMD) (16,31). Several factors limit the effectiveness of the iRED as a countermeasure to spaceflight-induced musculoskeletal de- conditioning. First, the peak resistance is limited to 136 kg (300 lb) (26); this is less than the resistance shown to be effective in previous bed rest studies (5,6,27). Further, con- sidering that body mass will not contribute to overall resis- tance in spaceflight, a 75-kg astronaut who performed a squat (SQ) with the iRED’s peak resistance on the ISS would experience a load roughly equivalent to the resistance from performing a SQ with only 60 kg of load in normal gravity (20). Second, during the eccentric portion of the movement, the force is only È70% of the corresponding concentric force (26), and a lack of eccentric resistance may compromise strength gains because of a suboptimal intensity (9). Finally, the iRED provides a variable resistance in which force increases as the cable is extended farther from the iRED. During closed-chain exercises (i.e., SQ, heel raise (HR), and dead lift (DL)), the iRED may be providing in- sufficient resistance at the bottom of the movement, where the muscles are most active (11), and greater resistance at the top, where the muscles are working less owing to an in- creased mechanical advantage (4). Address for correspondence: James A. Loehr, M.S., Space Physiology and Countermeasures, NASA Johnson Space Center, 2101 NASA Parkway, Mail code: SK3, Houston, TX 77058; E-mail: james.a.loehr@nasa.gov. 1Deceased. Submitted for publication October 2009. Accepted for publication April 2010. 0195-9131/11/4301-0146/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE Ò Copyright Ó 2010 by the American College of Sports Medicine DOI: 10.1249/MSS.0b013e3181e4f161 146 APPLIED SCIENCES