Lower Body Negative Pressure Treadmill Exercise Attenuates Simulated Space Flight‐Induced Reductions of Balance Abilities in Males but not Females

Abstract

Spaceflight causes sensorimotor adaptations that result in balance deficiencies upon return to a gravitational environment. Lower Body Negative Pressure (LBNP) treadmill exercise has been shown to protect against deconditioning in various other physiological systems during simulated spaceflight. Therefore, we hypothesized that LBNP treadmill exercise prevents balance losses in both male and female identical twins during 30 days of 6° head‐down‐tilt (HDT) bed rest. Fifteen (8M and 7F) identical twin sets participated in 30 days of bed rest. Within each twin pair, one twin was randomly assigned to an exercise group that performed 40 min of supine LBNP treadmill exercise set to generate 1.0–1.2 body weight, followed by 5 min of static LBNP, 6 days/wk. Their identical sibling was assigned to a non‐exercise control group. 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 to controls, subjects in the LBNP treadmill exercise group showed significantly attenuated losses of standing rail balance time, with prevention of 63% of the loss in men, but without a significant prevention in women (41%). In addition, LBNP treadmill exercise mitigated decreases in rail walk time in men, but not in women. Therefore, treadmill exercise within LBNP during spaceflight may maintain balance control; yet this protective effect may, to some extent, depend on gender.Support or Funding InformationThis study was funded by NASA grants NAG 9‐1425, NCC2‐1133, NNX10AM18G, and NNX13AJ12G, NIH grant to the UCSD GCRC M01 RR00827. BRM was supported by National Space Biomedical Research Institute through NCC 9‐58. We thank our outstanding twins and staff at the UCSD General Clinical Research Center, as well as the UCSD Faculty Mentorship Program and the 2015 Julia Brown Research Scholarship.