title: Facial immersion bradycardia in teenagers and adults accustomed to swimming.
abstract: We compared heart rate and breath-hold duration during facial immersion in teenagers, 11-14 years (N = 6), 15-18 years (N = 6) and adults, 33-48 years (N = 11). The subjects were members of a competitive swimming club, and were familiar with facial immersion. In contrast to the results of a previous study (J. Appl. Physiol. 63 (1987) 665) in which naïve subjects were used, the 11-14 group were able to breath-hold as long as adults (mean +/- SE, 47+/-6 vs. 46+/-4 s). This allowed time for the full development of bradycardia. Pre-immersion heart rate was significantly higher in young teens than in adults (100+/-4 vs. 78+/-3 b.p.m.). Heart rate after 30 s of head immersion was statistically identical (young teens, 65+/-5 b.p.m.; adults, 64+/-3 b.p.m.). Therefore, both the percentage reduction from pre-immersion rate and rate of fall in heart rate were greater in 11-14-year-olds than in adults. Oxygen loading increased breath-hold time in all groups, and slowed the onset of bradycardia in adults and older teens, but not in the 11-14-year-old group, during the first 10 s after immersion. We conclude that breath-hold time in teenagers is influenced by familiarity with underwater breath-holding. The resulting cardiovascular adjustments in 11-14-year-olds are intrinsically at least as intense as those in adults and seem to have a faster onset.
authors.affiliation: Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada. west@sask.usask.ca
authors.forename: N H
authors.initials: NH
authors.lastname: West
authors.forename: P F
authors.initials: PF
authors.lastname: McCulloch
authors.forename: P M
authors.initials: PM
authors.lastname: Browne
mesh_terms: D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001919:Bradycardia / Q000503:physiopathology*; D002648:Child; D004242:Diving / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D007101:Immersion / Q000503:physiopathology*; D007700:Kinetics; D008875:Middle Aged; D010100:Oxygen / Q000494:pharmacology; D010101:Oxygen Consumption / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology; D013550:Swimming / Q000502:physiology*
chemical_list: D010100:Oxygen