title: Face immersion increases vagal activity as assessed by heart rate variability.
abstract: We examined whether the diving reflex without breath-holding (face immersion alone) increases vagal activity, as determined by heart rate variability. A group of 15 men [mean age 20 (SD 3) years, height 172 (SD 5) cm, body mass 68 (SD 9) kg] performed 12 trials at various breathing frequencies (5, 10, 15, 20, 30 breaths x min(-1) and uncontrolled breath) with or without face immersion. The R-R intervals of the ECG and gas exchange variables were recorded during the 2 min of each trial. The subjects immersed their faces in 8 10 degrees C water while breathing through a short snorkel. The subject sat in the same position either with or without face immersion. The mean R-R interval (RRmean), standard deviations (SD[RR]) and coefficient of variance (CV[RR]) of the R-R interval were calculated from the R-R intervals during 30-120 s. The face immersion significantly increased SD(RR) and CV(RR) (P < 0.05), and increased RRmean (P < 0.05) at 20 breaths x min(-1). Face immersion itself had no effect on oxygen uptake, tidal volume, end-tidal O2 and CO2 partial pressures. The diving reflex without breath-holding increased the heart rate variability, indicating that face immersion alone increases vagal activity.
authors.affiliation: Faculty of Health and Sports Sciences, Osaka University Toyonaka, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Ishihara
authors.forename: A
authors.initials: A
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Osumi
authors.forename: T
authors.initials: T
authors.lastname: Yoshida
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000097:blood; D005145:Face / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007101:Immersion / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide