Musculoskeletal adaptations to training with the advanced resistive exercise device.

Abstract

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. To compare the musculoskeletal effects of resistance exercise training using the ARED with the effects of training with FW. 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 d·wk(-1) 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. 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 ≤ 0.05) in both groups. There were no significant differences between groups in any of the dependent variables at any time. 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.