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Navy

Lower body negative pressure leg press exercise machine

Compact, portable, lightweight exercise device for a zero gravity environment

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The leg press exercise apparatus is shown within an environmentally controlled LBNP box. Simulated legs are shown in brown and cooling ducts shown as green and red.

Exposure to the zero gravity of space and the microgravity of the moon has been shown to have detrimental health effects on humans including a reduction in heart size and blood volume, impaired balance control, changes in nervous system sensitivity, decreases in bone and muscle mass, and weakening of the immune system. Known as space deconditioning, it can lead to operational impairment. And because space flights are getting longer and the use of microgravity environments increasing, NASA and others have identified deconditioning as an ongoing issue.

Daily exercise has been used to prevent deconditioning and can counter bone demineralization and muscle loss while improving cardiovascular function. But studies indicate that exercise in space has lacked sufficient mechanical and physiological loads to maintain pre-flight musculoskeletal mass, strength, and aerobic capacity. As a partial solution, researchers have paired exercise with a Lower Body Negative Pressure (LBNP) box. The LBNP box is a sealed device into which the user is partially inserted. A seal near the waist allows a vacuum to be applied to the chamber, creating lower relative pressure on the legs which helps pull bodily fluids toward the feet. Pairing a treadmill to an LBNP box simulates the physiological and biomechanical features of upright exercise but the treadmill’s design lacks mobility and is large and heavy, making it unsuitable for space flight.

To address the above limitations, an engineer at the Naval Research Laboratory developed a compact, lightweight, and effective leg press exercise machine that works within a LBNP box. Importantly, the apparatus simulates both exercise and the daily activity of sitting. The exercise portion creates stress on the lower extremities by supplying variable resistance to reciprocating foot pedals. The resisting force increases as a function of leg extension to maximize work done by the user in each cycle of motion. The sitting portion of the exercise apparatus creates a resistance applied to the posterior side of the lower extremities by the use of an adjustable chair. Humans sit between six and eight hours per day, which means the posterior anatomy is accustomed to these forces.

By combining resistance exercise and lower body negative pressure, users will experience one or more times body weight in stress on their musculoskeletal, cardiovascular, and nervous systems. By achieving body weight or greater (artificial gravity) during exercise and two-thirds body weight during sitting, the gap between the pre-flight condition and the post-flight syndrome will decrease.

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