NASA has initiated the design and construction of an Advanced Resistive Exercise Device (ARED) for the International Space Station. The primary resistive mechanism of ARED is a pair of large vacuum cylinders containing pistons and a series of levers that attach to a lift bar. Using this device for bed rest studies poses unique design and logistical challenges. However, there are currently free weight systems that can readily be employed for supine exercise. Therefore, it may be possible to allow subjects to exercise with free weights, and to interpret results to be similar to those that would occur if ARED were used. On the other hand, it may be vital that ARED is used as the resistive exercise device during the bedrest studies if the loads applied to the body are different than with free weights. It is important to understand the differences between the two exercise modes to better understand training adaptations that will result from their use.
The purpose of this evaluation was to compare the ground reaction forces and ankle, knee and hip joint torques generated by human subjects during squat and deadlift exercises between the ARED, free weights, and the Smith machine.
Three subjects completed parallel squat exercise at 100, 120, 140 and 160 pounds using the ARED, free weights (FW) and the Smith machine (SM). Peak ground reaction forces were similar on each device at each load. Cross correlation coefficients between the ARED and FW and between the ARED and SM were similar at each load. Mean peak knee flexion angles were similar between the ARED and SM, but tended to be large with FW. These findings suggest that parallel squat exercises performed on the ARED illicit similar ground reaction forces as FW and SM. However, differences in knee range of motion between the ARED and FW coupled with similarities between the ARED and SM suggest that the ARED better replicated squat exercise performed on the SM.
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