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LBNP exercise protects aerobic capacity and sprint speed of female twins during 30 days of bed rest

¹Cardiovascular Laboratory, Wyle Integrated Science and Engineering Group, Houston, Texas; ²Department of Health, Exercise, and Sports Sciences, University of New Mexico, Albuquerque, New Mexico; ³Sonoma State University, Rohnert Park, California; ⁴University of North Texas Health Science Center, Fort Worth, Texas; and ⁵Department of Orthopaedic Surgery, University of California-San Diego Medical Center, San Diego, California

Submitted 18 November 2008 ; accepted in final form 18 December 2008

We have shown previously that treadmill exercise within lower body negative pressure (LBNPex) maintains upright exercise capacity (peak oxygen consumption, O_2peak) in men after 5, 15, and 30 days of bed rest (BR). We hypothesized that LBNPex protects treadmill O_2peak and sprint speed in women during a 30-day BR. Seven sets of female monozygous twins volunteered to participate. Within each twin set, one was randomly assigned to a control group (Con) and performed no countermeasures, and the other was assigned to an exercise group (Ex) and performed a 40-min interval (40–80% pre-BR O_2peak) LBNPex (51 ± 5 mmHg) protocol, plus 5 min of static LBNP, 6 days per week. Before and immediately after BR, subjects completed a 30.5-m sprint test and an upright graded treadmill test to volitional fatigue. These results in women were compared with previously reported reductions in O_2peak and sprint speed in male twins after BR. In women, sprint speed (–8 ± 2%) and O_2peak (–6 ± 2%) were not different after BR in the Ex group. In contrast, both sprint speed (–24 ± 5%) and O_2peak (–16 ± 3%) were significantly less after BR in the Con group. The effect of BR on sprint speed and O_2peak after BR was not different between women and men. We conclude that treadmill exercise within LBNP protects against BR-induced reductions in O_2peak and sprint speed in women and should prove effective during long-duration spaceflight.

spaceflight; microgravity; countermeasure; artificial gravity; sex; lower body negative pressure