title: Day-to-day variability in cardiorespiratory responses to hypoxic cycle exercise.
abstract: Repeatedly performing exercise in hypoxia could elicit an independent training response and become an unintended co-intervention. The primary purposes of this study were to determine if hypoxic exercise responses changed across repeated testing and to assess the day-to-day variability of commonly used measures of cardiorespiratory and metabolic responses to hypoxic exercise. Healthy young males (aged 23 ± 2 years) with a maximal O2 consumption of 50.7 ± 4.7 mL·kg(-1)·min(-1) performed 5 trials (H1 to H5) over a 2-week period in hypoxia (fraction of inspired oxygen = 0.13). Participants completed 3-min stages at 20%, 40%, 60%, and 10% of individual peak power. With increasing cycle exercise intensity there were increases in minute ventilation, O2 consumption, CO2 production, respiratory exchange ratio, heart rate (HR), blood lactate concentration, and ratings of perceived exertion for legs and respiratory system along with a reduction in oxyhaemoglobin saturation (%SpO2) (all p < 0.001). There were no systematic changes from H1 to H5 (p > 0.05). Most measures were highly repeatable across testing sessions with the coefficient of variation (CV) averaging ≤10% of the mean value in all variables except O2 consumption (17%), CO2 production (11%) and blood lactate concentration (17%). For HR and %SpO2 the CV was <5%. The exercise protocol did not elicit a training response when repeated 5 times during a 2-week period and the variability of exercise responses was low. We conclude that this protocol allows detection of small changes in cardiorespiratory responses to hypoxic exercise that might occur during exposure to hypoxia.
authors.affiliation: a Life Sciences, Quest University, Squamish, BC, Canada.
authors.forename: Meaghan J
authors.initials: MJ
authors.lastname: MacNutt
authors.forename: Carli M
authors.initials: CM
authors.lastname: Peters
authors.forename: Catherine
authors.initials: C
authors.lastname: Chan
authors.forename: Jason
authors.initials: J
authors.lastname: Moore
authors.forename: Serena
authors.initials: S
authors.lastname: Shum
authors.forename: A William
authors.initials: AW
authors.lastname: Sheel
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001642:Bicycling / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010108:Oxyhemoglobins / Q000378:metabolism; D011446:Prospective Studies; D012119:Respiration; D055815:Young Adult
chemical_list: D010108:Oxyhemoglobins; D002245:Carbon Dioxide; D019344:Lactic Acid
keywords: acclimatation; acclimatization; blood lactate; consommation d’oxygène; haute altitude; high altitude; intensité de l’effort perçue; lactate sanguin; oxygen consumption; rating of perceived exertion; ventilation