Supine LBNP exercise maintains exercise capacity in male twins during 30-d bed rest.
BACKGROUND
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 (LBNP(ex)) maintains upright exercise responses in men after 5 and 15 d of bed rest, as a simulation of microgravity.


OBJECTIVE
The purpose of this study was to determine whether LBNP(ex) 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(ex) (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, 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.
Lee
Stuart M C
SM
Wyle Laboratories, Inc., Life Sciences Group, Houston, TX 77058, USA. stuart.lee-1@mail.nasa.gov
Schneider
Suzanne M
SM
Boda
Wanda L
WL
Watenpaugh
Donald E
DE
Macias
Brandon R
BR
Meyer
R Scott
RS
Hargens
Alan R
AR
D000328:Adult; D000886:Anthropometry; D001510:Bed Rest; D005080:Exercise Test / Q000379:methods*; D018470:Gravity, Altered; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010953:Plasma Volume; D011187:Posture / Q000502:physiology*; D016683:Supine Position; D014427:Twins; D018474:Weightlessness Simulation