Musculoskeletal risks need to be addressed due to loss of muscle mass and strength, along with decreased aerobic capacity brought on by the mechanical unloading of the body and by the lack of weighted objects handled and moved by astronauts. Current exercise protocols on the International Space Station (ISS), including resistive and aerobic exercises on the ARED, ergonomic bicycle, and treadmill, are effective in preserving some, but not all muscle mass and function. Evidence suggests that the combination of orthostatic fluid distribution and load-bearing exercise are more efficient together than either one in isolation for preventing cardiovascular and musculoskeletal deconditioning. The mobile Gravity Suit is designed to work in combination with some aerobic- and resistance exercises, thereby increasing the efficacy.
In order to address these issues, this study will validate the prototype of an intravehicular mobile countermeasure suit, which consists of lower body negative pressure (LBNP) trousers and vest to reproduce the effects of gravitational stress during space flight. Use of the suit will re-introduce habitual Earth-like, gravitational fluid shifts while providing an axial mechanical load for an integrated countermeasure to maintain cerebral and ocular health, cardiovascular and aerobic capacity, as well as musculoskeletal strength and function. The mobile gravity suit is comfortable enough to be worn for six to eight hours a day without interfering with everyday in-flight activities and flexible enough to be combined with some forms of exercise.
The study will be comprised of a total of eight subjects, four of which will be female. Initial testing will serve as proof of concept to demonstrate caudal fluid shift and mechanical loading. Additionally, mechanical loading and axial compression simulating the effect of gravitational mechanical stress on the body will be demonstrated. Maintained flexibility of the joints to allow for flexibility both involved in daily activity and in-flight work on the ISS as well as potential combination with some forms of restrictive and/or aerobic exercise is an important aim. Finally, long duration use will be demonstrated by continues wear of the suit for 8-hours (subject will be allowed breaks for use of the restroom etc.) The long-term trial will be proof of concept and the subject will spend eight hour in simulated microgravity (by supine posture) and will be randomly assigned to either a control arm of the trial (not wearing the Suit) or to the intervention arm of the trial (wearing the suit) on two separate days. To conduct this part of the experiment, the subjects will be placed in a supine position. On each day of the experiment, the measurements described below will be performed at rest, during, and after thirty minutes of repeated moderate exercise. Specific measurements will include:
Investigators expect to deliver a comfortable intravehicular mobile Gravity Suit comprised of LBNP trousers and attached spine loading vest to re-introduce daily, Earth-like fluid shifts and axial mechanical loads as an integrative countermeasure during long-term micro- or fractional gravity. They expect that the 20 mmHg LBNP provided by the Gravity Suit with generated ground reaction forces (GRFs) will reproduce previously documented effects of conventional LBNP (rigid box) on caudal fluid shift to unload cerebral structures to mitigate SANS, Investigators also expect that it will provide enough comfort and range of motion at the desired GRFs and axial mechanical loads to be worn for six to eight hours per day, including during moderate exercise such as e.g. rowing, squats, or jogging.
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