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

Stuart M. C. Lee, Suzanne M. Schneider, Wanda L. Boda

• 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-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, 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.