title: Supine LBNP exercise maintains exercise capacity in male twins during 30-d bed rest.
abstract: 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.
authors.affiliation: Wyle Laboratories, Inc., Life Sciences Group, Houston, TX 77058, USA. stuart.lee-1@mail.nasa.gov
authors.forename: Stuart M C
authors.initials: SM
authors.lastname: Lee
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Schneider
authors.forename: Wanda L
authors.initials: WL
authors.lastname: Boda
authors.forename: Donald E
authors.initials: DE
authors.lastname: Watenpaugh
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Macias
authors.forename: R Scott
authors.initials: RS
authors.lastname: Meyer
authors.forename: Alan R
authors.initials: AR
authors.lastname: Hargens
mesh_terms: 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