title: Peak exercise oxygen uptake during and following long-duration spaceflight.
abstract: This investigation was designed to measure aerobic capacity (V̇o2peak) during and after long-duration International Space Station (ISS) missions. Astronauts (9 males, 5 females: 49 ± 5 yr, 77.2 ± 15.1 kg, 40.6 ± 6.4 ml·kg(-1)·min(-1) [mean ± SD]) performed peak cycle tests ∼90 days before flight, 15 days after launch, every ∼30 days in-flight, and on recovery days 1 (R + 1), R + 10, and R + 30. Expired metabolic gas fractions, ventilation, and heart rate (HR) were measured. Data were analyzed using mixed-model linear regression. The main findings of this study were that V̇o2peak decreased early in-flight (∼17%) then gradually increased during flight but never returned to preflight levels. V̇o2peak was lower on R + 1 and R + 10 than preflight but recovered by R + 30. Peak HR was not different from preflight at any time during or following flight. A sustained decrease in V̇o2peak during and/or early postflight was not a universal finding in this study, since seven astronauts were able to attain their preflight V̇o2peak levels either at some time during flight or on R + 1. Four of these astronauts performed in-flight exercise at higher intensities compared with those who experienced a decline in V̇o2peak, and three had low aerobic capacities before flight. These data indicate that, while V̇o2peak may be difficult to maintain during long-duration ISS missions, aerobic deconditioning is not an inevitable consequence of long-duration spaceflight.
authors: Wyle Science, Technology & Engineering Group, Houston, Texas;
authors: Alan D
authors: AD
authors: Moore
authors: University of Houston, Houston, Texas; meghan.e.everett@nasa.gov.
authors: Meghan E
authors: ME
authors: Downs
authors: Wyle Science, Technology & Engineering Group, Houston, Texas;
authors: Stuart M C
authors: SM
authors: Lee
authors: National Aeronautics and Space Administration Johnson Space Center, Houston, Texas;
authors: Alan H
authors: AH
authors: Feiveson
authors: Danish Aerospace Company, Odense, Denmark; and.
authors: Poul
authors: P
authors: Knudsen
authors: Universities Space Research Association, Houston, Texas.
authors: Lori
authors: L
authors: Ploutz-Snyder
mesh_terms: D018480:Astronauts; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D013026:Space Flight / Q000379:methods; D013997:Time Factors; D014893:Weightlessness
chemical_list: D010100:Oxygen
keywords: International Space Station; aerobic capacity; weightlessness