Generating waist area-dependent ground reaction forces for long-duration spaceflight

摘要

Prolonged microgravity exposure greatly weakens the bones and muscles of astronauts. This is a critical biomechanical issue for astronauts as they may be more prone to bone fractures. To combat this issue, lower body negative pressure (LBNP) is a concept that generates artificial gravitational forces that may help strengthen bones and muscles during long-term spaceflight. Negative pressure, defined as below ambient pressure, is applied within a chamber that encompasses the lower half of the body. By increasing the negative pressure, more ground reaction forces (GRFs) are generated beneath the subject & rsquo;s feet. We hypothesize that increasing the cross-sectional area (CSA) of the subject & rsquo;s waist will generate greater GRFs beneath the subject & rsquo;s feet. Six healthy subjects volunteered to participate under two different experimental conditions: 1) original CSA of their waist and 2) larger CSA of their waist. In both conditions the subjects were suspended in a supine position (simulated microgravity) along with a weight scale beneath their feet. Negative pressures ranged from zero to 50 mmHg, increasing in increments of 5 mmHg. At-50 mmHg, original CSAs generated 1.18 +/- 0.31 (mean +/- SD) of their normal bodyweight. Subjects generated about one bodyweight at-45 mmHg using their original waist CSA. At-50 mmHg, larger CSAs generated 1.46 +/- 0.31 of their normal bodyweight. Subjects generated about one bodyweight at-35 mmHg using their larger waist CSA. These data support our hypothesis. This novel technique may apply less stress to the cardiovascular system and conserve power for exercise in the spacecraft.