title: The metabolic cost of an integrated exercise program performed during 14 days of bed rest.
abstract: BACKGROUND
  Exercise countermeasures designed to mitigate muscle atrophy during long-duration spaceflight may not be as effective if crewmembers are in negative energy balance (energy output > energy input). This study determined the energy cost of supine exercise (resistance, interval, aerobic) during the spaceflight analogue of bed rest.
  
  
  METHODS
  Nine subjects (eight men and one woman; 34.5 +/- 8.2 yr) completed 14 d of bed rest and concomitant exercise countermeasures. Body mass and basal metabolic rate (BMR) were assessed before and during bed rest. Exercise energy expenditure was measured during and immediately after [excess post-exercise oxygen consumption (EPOC)] each of five different exercise protocols (30-s, 2-min, and 4-min intervals, continuous aerobic, and a variety of resistance exercises) during bed rest.
  
  
  RESULTS
  On days when resistance and continuous aerobic exercise were performed daily, energy expenditure was significantly greater (2879 +/- 280 kcal) than 2-min (2390 +/- 237 kcal), 30-s (2501 +/- 264 kcal), or 4-min (2546 +/- 264 kcal) exercise. There were no significant differences in BMR (pre-bed rest: 1649 +/- 216 kcal; week 1: 1632 +/- 174 kcal; week 2:1657 +/- 176 kcal) or body mass (pre-bed rest: 75.2 +/- 10.1 kg; post-bed rest: 75.2 +/- 9.6 kg).
  
  
  CONCLUSIONS
  These findings highlight the importance of energy balance for long-duration crewmembers completing a high-intensity exercise program with multiple exercise sessions daily.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Scott
authors.forename: Kyle
authors.initials: K
authors.lastname: Hackney
authors.forename: Meghan
authors.initials: M
authors.lastname: Downs
authors.forename: Jamie
authors.initials: J
authors.lastname: Guined
authors.forename: Robert
authors.initials: R
authors.lastname: Ploutz-Snyder
authors.forename: James
authors.initials: J
authors.lastname: Fiedler
authors.forename: David
authors.initials: D
authors.lastname: Cunningham
authors.forename: Lori
authors.initials: L
authors.lastname: Ploutz-Snyder
mesh_terms: D001510:Bed Rest; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D013026:Space Flight