Resistance Exercise Machine within Lower Body Negative Pressure for Counteracting Effects of Microgravity

Abstract

Physiological deconditioning is a critical problem in space, especially during long-term missions. Resistance exercise, coupled with lower body negative pressure (LBNP), has been shown to be effective in counteracting some of the deconditioning related problems. This paper describes the development of a compact and effective resistance exercise machine that works within an existing environmentally controlled LBNP Box, and is designed to simulate both exercise and sitting, to decrease microgravity-induced deconditioning by simulating physiological and biomechanical features of upright exercise and daily activities. Theoretical calculations are carried out to determine whether kinematics, musculoskeletal loadings, and metabolic rate during supine exercise within the existing LBNP Box are similar to those of an upright posture in Earth gravity (1G). Preliminary results show subjects that use the resistance machine presented in this paper will be able to elicit loads comparable to exercise on Earth, since the ground reaction forces are greater than their body weight (BW). The largest single-leg forces during resistance exercise are 1.16 BW (232 lbs) during supine position when γ, the angle between the horizontal and the ground pivot on the right side of the mechanism, equals 187 degrees and minimal at 0.68 BW (136 lbs) when γ equals 177 degrees. At the lowest setting of the machine, peak resistance of the foot pedal during the outward stroke is 196 lbf. This force, added to the force due to the 50 mmHg of negative differential pressure, gives a total force of 400 lb, which is 2 BW. The results suggest that this machine can be used to collect and establish a database under both terrestrial conditions and microgravity environments, such as the International Space Station (ISS), to enhance medical researchers’ understanding of how LBNP paired with exercise impacts osteoporosis, orthostatic intolerance, and cardiovascular health.