Treadmill exercise within lower-body negative pressure attenuates simulated spaceflight-induced reductions of balance abilities in men but not women

• Published in: NPJ microgravity 2016-06, Vol.2 (1), p.16022-16022, Article 16022
• Main Authors: Macaulay, Timothy R, Macias, Brandon R, Lee, Stuart MC, Boda, Wanda L, Watenpaugh, Donald E, Hargens, Alan R
• Format: Article
• Language: English
• Subjects: 631/443; 692/308/575; Applied Microbiology; Biomedical and Life Sciences; Biotechnology; Classical and Continuum Physics; Immunology; Life Sciences; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics
• ISSN: 2373-8065; 2373-8065
• DOI: 10.1038/npjmgrav.2016.22

Spaceflight causes sensorimotor adaptations that result in balance deficiencies on return to a gravitational environment. Treadmill exercise within lower-body negative pressure (LBNP) helps protect physiological function during microgravity as simulated by bed rest. Therefore, we hypothesized that treadmill exercise within LBNP would prevent balance losses in both male and female identical twins during 30 days of 6° head-down tilt bed rest. Fifteen (seven female and eight male) identical twin sets participated in this simulation of microgravity. Within each twin pair, one twin was randomly assigned to an exercise group that performed 40 min of supine treadmill exercise within LBNP set to generate 1.0–1.2 body weight, followed by 5 min of static feet-supported LBNP, 6 days per week. Their identical sibling was assigned to a non-exercise control group with all other bed rest conditions equivalent. Before and immediately after bed rest, subjects completed standing and walking rail balance tests with eyes open and eyes closed. In control subjects, standing rail balance times (men: −42%, women: −40%), rail walk distances (men: −44%, women: −32%) and rail walk times (men: −34%, women: −31%) significantly decreased after bed rest. Compared with controls, treadmill exercise within LBNP significantly attenuated losses of standing rail balance time by 63% in men, but the 41% attenuation in women was not significant. Treadmill exercise within LBNP did not affect rail walk abilities in men or women. Treadmill exercise within LBNP during simulated spaceflight attenuates loss of balance control in men but not in women. Exercise: Men's balance benefits more than women Men and women may respond differently to measures to counteract balancing difficulties caused by long-duration spaceflight. The suggestion comes from a microgravity simulation study by US researchers led by Timothy Macaulay at the University of California, San Diego. Eight pairs of male and seven pairs of female identical twins undertook 30 days of bed-rest with their heads tilted downward–a standard method to simulate the microgravity conditions of spaceflight. One member of each pair exercised regularly with a treadmill while still lying supine in negative pressure conditions on their lower body. At the end of the study, the males who had exercised performed significantly better than their twins in a single-leg balancing test. However, the females who exercised showed no statistically significant benefit