Abstract
Spaceflight Associated Neuro-ocular Syndrome, bone decalcification, and muscle atrophy are among the most prevalent risks associated with long-duration spaceflight. Implementing the lower body negative pressure (LBNP) method is a potential countermeasure for these risks. LBNP counteracts head-ward fluid shifts and generates ground-reaction forces (GRFs). GRFs are beneficial for maintaining bones and muscles by producing gravity-like loads experienced on Earth. Currently, LBNP devices are large/bulky, and usually require the subject to maintain a stationary position. However, our new mobile gravity suit is relatively small, untethered, and flexible in order to improve mobility in space. We hypothesized that this novel mobile gravity suit generates greater GRFs than a standard LBNP chamber. While lying supine, GRF data were recorded in both devices using foot sole sensors and a weight scale. At -40 mmHg, the gravity suit generated a mean maximum bodyweight of 125 ± 22% (P < 0.02) whereas the standard LBNP chamber generated 91 ± 24%. The standard LBNP chamber generated a single force on the stationary subject, which was expressed as AW(LBNP) = GRF, where Aw = cross-sectional area (CSA) of subject’s waist. However, the mobile gravity suit generated an additional force based on the following equation, (AF + AW)LBNP = GRF, where AF = CSA of subject’s feet. The additional force was further expressed as F1 + F2 = AF × LBNP, where F1 = spinal loading force, F2 = waist shear force, and AF × LBNP = the total downward foot force. Thus, the mobile gravity suit produces higher percentages of bodyweight due to the suit’s novel design.
Highlights
Spaceflight Associated Neuro-ocular Syndrome (SANS), previously known as Visual Impairment Intracranial Pressure (VIIP), is a major risk associated with long-duration spaceflight
Optic disk edema, posterior globe flattening, decreased near vision, and hyperopic shifts are hallmarks of SANS (Zhang and Hargens, 2018). This risk stems from the lack of Abbreviations: advanced resistive exercise device (aRED), Advanced Resistive Exercise Device; GRF, Ground-Reaction Force; intravehicular activity (IVA), Intravehicular Activity; lower body negative pressure (LBNP), Lower Body Negative Pressure; SANS, Spaceflight Associated Neuro-ocular Syndrome; VIIP, Visual Impairment Intracranial Pressure
As for the LBNP chamber GRF data, we recruited a total of six healthy subjects (3 males and 3 females) with an average age ± SD: 23.3 ± 4.3 years, FIGURE 1 | (A) Mobile gravity suit without negative pressure activation and (B) mobile gravity suit with negative pressure activation (−10 mmHg)
Summary
Spaceflight Associated Neuro-ocular Syndrome (SANS), previously known as Visual Impairment Intracranial Pressure (VIIP), is a major risk associated with long-duration spaceflight. Optic disk edema, posterior globe flattening, decreased near vision, and hyperopic shifts are hallmarks of SANS (Zhang and Hargens, 2018) This risk stems from the lack of Abbreviations: aRED, Advanced Resistive Exercise Device; GRF, Ground-Reaction Force; IVA, Intravehicular Activity; LBNP, Lower Body Negative Pressure; SANS, Spaceflight Associated Neuro-ocular Syndrome; VIIP, Visual Impairment Intracranial Pressure. An astronaut’s movement between modules, aerobic activity, and extra-vehicular activity components are amongst the leading causes of musculoskeletal injuries (Scheuring et al, 2009). This becomes a major concern as astronauts return from space to weight-bearing environments, such as Earth or even potentially Mars. In order to minimize musculoskeletal loss and injuries, it is essential to develop effective techniques that reproduce gravitational forces for microgravity conditions
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