Supine LBNP Exercise Maintains Exercise Capacity in Male Twins during 30-d Bed Rest.

摘要

INTRODUCTION:: Exercise capacity is reduced after both short- and long-duration exposures to microgravity. Previously, we have documented that supine treadmill exercise within lower-body negative pressure (LBNPex) maintains upright exercise responses in men after 5 and 15 d of bed rest, as a simulation of microgravity. PURPOSE:: The purpose of this study was to determine whether LBNPex would protect against loss of upright exercise capacity (V O2peak) and sprint performance during a longer-duration bed rest. METHODS:: Eight sets of male twins participated in 30 d of bed rest. Within each twin pair, one was randomly assigned to a control group (CON) who performed no exercise, and the other was assigned to an exercise group (EX) that performed a 40-min interval (40-80% pre-bed rest V O2peak) LBNPex (55 +/- 4 mm Hg) protocol, plus 5 min of resting LBNP, 6 d.wk. LBNP produced footward force equivalent to 1.0-1.2 body weight. Before and after bed rest, subjects completed an upright graded exercise test to volitional fatigue and a sprint test of 30.5 m. RESULTS:: After bed rest, V O2peak was decreased significantly in the CON subjects (-23 +/- 4%, P < 0.01) but was maintained in the EX subjects (-3 +/- 3%). Sprint time was increased in the CON subjects (24 +/- 8%, P < 0.05) but was maintained in the EX group (8 +/- 2%). CONCLUSIONS:: This exercise countermeasure protocol may help prevent microgravity-induced deconditioning during long-duration space flight.