EFFECTS OF SUPINE LBNP EXERCISE ON SPRINT AND BALANCE ABILITY AFTER 30 DAYS OF BEDREST IN 6 DEGREE HEAD DOWN TILT

Abstract

Muscle mass and bone density are lost during exposure to microgravity. Exercise protocols must be developed which will minimize losses during prolonged spaceflight. PURPOSE We hypothesized supine treadmill exercise in lower body negative pressure (LBNP) would decrease losses of sprint and balance ability in subjects exposed to microgravity, simulated by 30 days of bedrest in 6 degree head down tilt. METHODS Twenty identical twins (female, n = 6; male, n = 14) were tested PRE and POST bedrest for one foot rail balance eyes closed (EC) (up to 30 sec), sprint time (30.5m), walk time (30.5m) and rail walk balance eyes open (EO) (4.9m beam). Each twin was randomly assigned to: 1) an experimental group that ran on a vertically oriented treadmill 40 minutes, 6 days per week in LBNP (EXP) or 2) a control group that did not (CON). Rail walk performance was determined by averaging percent distance traveled divided by total time. RESULTS EXP performed significantly better (P < 0.01) than CON for sprint times EXP 5.8 (0.84)s; CON 6.8(1.66)s. EXP also performed better (but not significantly) than CON for walking times EXP 25.1(2.95)s; CON 27.8 (7.99) and rail walk EXP 9.8 (2.56)s−1; CON 8.6(3.17))s−1 (mean (SD)). Significant differences (P <0.05) existed between PRE and POST performances for the subsequent reported comparisons. PRE sprint times were significantly shorter than POST times for both CON (5.2 (0.63)s vs. 6.8 (1.66)s) and EXP (5.2 (0.71)s vs. 5.8 (0.84)s). PRE walk times were significantly shorter than POST times for both CON (22.9 (1.92)s vs. 27.8 (7.99)s) and EXP (23.1 (2.41)s vs. 25.1 (2.94)s). Balance times EC were longer PRE than POST for both CON (24.5(9.61)s vs 16.6(13.58)s) and EXP (21.3(10.32)s vs 16.4(10.31)s). CONCLUSION A trend in results suggest exercise in LBNP may reduce loss of sprint and balance ability after 30 days of bedrest in 6 degree head down tilt. Supported by National Aeronautics and Space Administration grant #199–26–12–34