title: Effect of exercise on night periodic breathing and loop gain during hypoxic confinement.
abstract: OBJECTIVE
  Hypoxic exercise exacerbates periodic breathing in otherwise healthy, awake humans. Interactions between sleep, exercise and hypoxic exposure have not been fully elucidated.
  
  
  METHODS
  Fourteen men were confined 10 days to a simulated altitude of 4175 m (FIO2 = 0.139; PIO2 = 88 mm Hg). They were randomly assigned to an exercise intervention of 2 × 60-min cycle exercise/day at 50% of their hypoxia-specific peak power output (exercise, n = 8), or they completed no exercise (control, n = 6, random order). Sleep and breathing were objectively assessed via full polysomnography on night 1, after 14-h acute exposure (N1), and again on night 10 (N10).
  
  
  RESULTS
  The exercise group spent more time in light sleep than control on N10 (95% confidence interval (CI): 8.5-15.0%; P = 0.013) and experienced more stage shifts (CI: 13-44; P = 0.023) on both nights compared with control. The exercise group experienced more apnoea-hypopnoea (AH) events per hour compared with control (CI: 1-110; P = 0.046); AH events that were associated with night desaturations were also higher on N1 (exercise: 397 ± 320, control: 124 ± 205, P = 0.047) and N10 (exercise: 375 ± 229, control: 110 ± 138, P = 0.028, CI: 49-489 total events; P = 0.020). The length of hyperpnoea was increased from 12.8 ± 2.2 s on N1 to 14.6 ± 2.7 s on N10 (P = 0.008), and thus, total cycle length also increased (P = 0.002) in both cohorts. Mean pooled duty ratios were 0.68 ± 0.02 on N1 and 0.69 ± 0.02 on N10 (group effect P = 0.617).
  
  
  CONCLUSIONS
  Daily, moderate-intensity exercise in normobaric hypoxia equivalent to 4175 m exacerbated AH events, and negatively affected sleep architecture in exercisers compared with matched controls.
authors.affiliation: Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia.|Institute of Clinical Neurophysiology, Division of Neurology, University Medical Centre, Ljubljana, Slovenia.
authors.forename: Shawnda A
authors.initials: SA
authors.lastname: Morrison
authors.affiliation: Institute of Clinical Neurophysiology, Division of Neurology, University Medical Centre, Ljubljana, Slovenia.
authors.forename: Andrej
authors.initials: A
authors.lastname: Pangerc
authors.affiliation: Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Ola
authors.initials: O
authors.lastname: Eiken
authors.affiliation: Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Igor B
authors.initials: IB
authors.lastname: Mekjavic
authors.affiliation: Institute of Clinical Neurophysiology, Division of Neurology, University Medical Centre, Ljubljana, Slovenia.
authors.forename: Leja
authors.initials: L
authors.lastname: Dolenc-Groselj
mesh_terms: D000328:Adult; D000531:Altitude; D015444:Exercise / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D064797:Physical Conditioning, Human / Q000009:adverse effects / Q000502:physiology; D017286:Polysomnography; D012119:Respiration; D012891:Sleep Apnea Syndromes / Q000209:etiology; D012894:Sleep Stages; D055815:Young Adult
keywords: central sleep apnoea; high altitude; loop gain; sleep