Supine LBNP exercise maintains exercise capacity in male twins during 30-d bed rest

Purpose: The purpose of this study was to determine whether LBNPex would protect against loss of upright exercise capacity (VO2peak) 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 VO2peak) LBNP,x (55 +/- 4 turn Hg) protocol, plus 5 min of resting LBNP, 6 d.wk(-1). 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, VO2peak 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.