Effects Of Supine Lower Body Negative Pressure Exercise On Sprint And Balance In Women And Men After 30 Days Of Bedrest In 6 Degree Head Down Tilt

Abstract

INTRODUCTION Muscle mass and bone density decrease during exposure to microgravity and neuromotor function is impaired. Exercise protocols must be developed that minimize these losses during prolonged spaceflight. PURPOSE We hypothesized supine treadmill exercise against lower body negative pressure (LBNP) would prevent losses of sprint and balance ability in subjects exposed to prolonged microgravity, simulated by 6-degree head down bed rest (BR). METHODS Fifteen sets of identical twins (female, n = 7; male, n = 8) completed a 30-day BR study. They were tested pre- and post-BR for sprint time and walk back over 30.5m, one foot rail balance with eyes closed (EC) (up to 30 sec), rail walk balance down a 4.9m beam with eyes open (EO). Each twin was randomly assigned to: 1) an experimental group that ran on a vertically oriented treadmill 40 minutes, 6 days per week against −55 ± 4mmHg LBNP (EXP) or 2) a control group that did no exercise (CON). Rail walk performance was determined by averaging percent distance traveled divided by total time. Pre- and post-BR results were compared using repeated measures ANOVA, and are reported as mean±SD. RESULTS The male CON group had significantly shorter (p<0.05) left foot balance times EC POST 7.5 ± 7.5 s versus PRE 23.6 ± 11.9 s. Rail walk (EO) was significantly less (p<0.05) POST 8.8 ± 3.2%d/t versus PRE 10.2 ± 3.6%d/t with no differences between any other groups. Female CON subjects had significantly slower sprint times after bed rest (Pre: 6.1±04; Post: 8.7±1.4 sec). All other groups maintained sprint times pre- and post-BR. Walk back times were significantly slower in all groups after bed rest (Pre: 23.2±1.8; Post: 26.8±4.6sec). Left foot balance (EO) was significantly less (p<0.05) POST 27.04±5.2s versus PRE 30±0 s. CONCLUSION The results suggest exercise in LBNP may maintain sprint times in female subjects and some balance parameters after 30 days of bedrest in 6 degree head-down tilt. Supported by NASA grant#NAG9-1425 & NIH grant M01 RR00827 to the UCSD GCRC