title: Diurnal variations of post-exercise parasympathetic nervous reactivation in different chronotypes.
abstract: The purpose of this study was to investigate the diurnal variation and chronotype differences, i.e., in morning-types and evening-types, in post-exercise vagal reactivation. Twelve healthy male college students who were classified as morning-type (6) and evening-type (6), based on responses to a questionnaire, participated in this study. Postexercise vagal reactivation was assessed as the time constant of the beat-by-beat heart rate decrease for the first 30 sec after exercise (T30) at an intensity lower than the ventilatory threshold. The subjects performed 3-min cycle ergometer exercise at an intensity corresponding to 80% of the ventilatory threshold after a 1 min warm-up exercise in the morning (7:00 - 8:00) and evening (17:00 - 18:00) to obtain the T30. A significant interaction (chronotype-by-time) effect was found for T30. The morning value of the T30 in evening-type subjects was significantly larger than their evening value and the morning value in morning-type subjects. There was no significant interaction effect for heart rate and oxygen uptake during exercise. These results suggest that diurnal variation in post-exercise vagal reactivation is different between morning-type and evening-type, and post-exercise vagal reactivation in evening-type individuals is sluggish in the morning.
authors.affiliation: Doctoral Program in Health and Sports Sciences, University of Tsukuba, Ibaraki, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Sugawara
authors.forename: Y
authors.initials: Y
authors.lastname: Hamada
authors.forename: T
authors.initials: T
authors.lastname: Nishijima
authors.forename: M
authors.initials: M
authors.lastname: Matsuda
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002909:Chronobiology Phenomena; D002940:Circadian Rhythm / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010275:Parasympathetic Nervous System / Q000502:physiology*; D014630:Vagus Nerve