title: V̇O2 and HR kinetics before and after International Space Station missions.
abstract: Heart rate (HR), pulmonary and muscle oxygen uptake ([Formula: see text]O2pulm, [Formula: see text]O2musc) kinetics after changes of work rate (WR) indicate regulatory characteristics related to aerobic metabolism. We analysed whether the kinetics of HR, [Formula: see text]O2pulm and [Formula: see text]O2musc are slowed after missions to the International Space Station (ISS). The changes of the kinetics were correlated with [Formula: see text]O2peak data.
  
  
  
  10 astronauts [4 females, 6 males, age: 48.0 ± 3.8 years, height: 176 ± 7 cm, mass: 74.5 ± 15.9 kg (mean ± SD)] performed an incremental test to determine [Formula: see text]O2peak (before missions on L-110 days, after return on R+1/+10/+36 days), and a cardio-respiratory kinetics test (CRKT) with randomized 30-80 W WR changes to determine HR, [Formula: see text]O2pulm and [Formula: see text]O2musc kinetics by time-series analysis (L-236/-73, R+6/+21). Kinetics were summarized by maximum and related lag of cross-correlation function (CCFmax, CCFlag) of WR with the analysed parameter.
  
  
  
  Statistically, significant changes were also found for CCFmax([Formula: see text]O2musc) between L-236 and R+6 (P = 0.010), L-236 and R+21 (P = 0.030), L-72 and R+6 (P = 0.043). Between pre-to-post mission change in [Formula: see text]O2peak and CCFmax(HR), a correlation was shown (r SP = 0.67, P = 0.017).
  
  
  
  The [Formula: see text]O2musc kinetics changes indicate aerobic detraining effects which are present up to 21 days following space flight. The correlations between changes in [Formula: see text]O2peak and HR kinetics illustrate the key role of cardiovascular regulation in [Formula: see text]O2peak. The addition of CRKT to ISS flight is recommended to obtain information regarding the potential muscular and cardiovascular deconditioning. This allows a reduction in the frequency of higher intensity testing during flight.
authors.affiliation: Institute of Physiology and Anatomy, German Sport University, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany. u.hoffmann@dshs-koeln.de.
authors.forename: U
authors.initials: U
authors.lastname: Hoffmann
authors.affiliation: Lamar University, Beaumont, TX, 77710, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Moore
authors.affiliation: Institute of Physiology and Anatomy, German Sport University, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Koschate
authors.affiliation: Institute of Physiology and Anatomy, German Sport University, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Drescher
mesh_terms: D000328:Adult; D015444:Exercise; D005260:Female; D006339:Heart Rate; D006801:Humans; D008168:Lung / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D010101:Oxygen Consumption; D013026:Space Flight; D014893:Weightlessness
keywords: Moderate exercise test; Muscular oxygen uptake; PRBS; Pulmonary oxygen uptake; Space flight