title: The effect of short-term intermittent hypoxic exposure on heart rate variability in a sedentary population.
abstract: While the effects of instantaneous, single-bout exposure to hypoxia have been well researched, little is known about the autonomic response during, or as an adaptation to, repeated intermittent hypoxic exposure (IHE) in a sedentary population. Resting heart rate variability (HRV) and exercise capacity was assessed in 16 participants (8 receiving IHE, [Hyp] and 8 receiving a placebo treatment [C]) before and after a 4-week IHE intervention. Heart rate variability was also measured during an IHE session in the last week of the intervention. Post-intervention, the root mean squared successive difference (rMSSD) increased substantially in Hyp (71.6 ± 52.5%, mean change ± 90% confidence limits) compared to C suggesting an increase in vagal outflow. However, aside from a likely decrease in submaximal exercise heart rate in the Hyp group (-5.0 ± 6.4%) there was little evidence of improved exercise capacity. During the week 4 IHE measurement, HRV decreased during the hypoxic exposure (reduced R-R interval: -7.5 ± 3.2%; and rMSSD: -24.7 ± 17.3%) suggesting a decrease in the relative contribution of vagal activity. In summary, while 4 weeks of IHE is unlikely to improve maximal exercise capacity, it may be a useful means of increasing HRV in people unable to exercise.
authors.affiliation: Department of Tourism, Sport and Society, Lincoln University , Christchurch , New Zealand.|School of Sport and Physical Education, University of Canterbury , Christchurch , New Zealand.
authors.forename: C A
authors.initials: CA
authors.lastname: Lizamore
authors.affiliation: Sports Doctors , Christchurch , New Zealand.
authors.forename: Y
authors.initials: Y
authors.lastname: Kathiravel
authors.affiliation: Department of Medicine, University of Otago , Christchurch , New Zealand.
authors.forename: J
authors.initials: J
authors.lastname: Elliott
authors.affiliation: Sportsmed , Christchurch , New Zealand.
authors.forename: J
authors.initials: J
authors.lastname: Hellemans
authors.affiliation: Department of Tourism, Sport and Society, Lincoln University , Christchurch , New Zealand.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hamlin
mesh_terms: D001794:Blood Pressure / Q000502:physiology; D015444:Exercise / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010507:Periodicity; D012146:Rest / Q000502:physiology; D057185:Sedentary Behavior; D013997:Time Factors
keywords: autonomic nervous system; health; interval hypoxia; physical fitness; sedentary lifestyle; simulated altitude