title: Time of day affects heart rate recovery and variability after maximal exercise in pre-hypertensive men.
abstract: Heart rate (HR) recovery (HRR) and variability (HRV) after exercise are non-invasive tools used to assess cardiac autonomic regulation and cardiovascular prognosis. Autonomic recovery is slower after evening than morning exercise in healthy individuals, but this influence is unknown in subjects with autonomic dysfunction, although it may affect prognostic evaluation. This study compared post-exercise HRR and HRV after maximal morning and evening exercise in pre-hypertensive men. Ten volunteers randomly underwent two maximal exercise tests conducted in the morning (8-10 a.m.) and evening (6-8 p.m.). HRR60s (HR reduction at 60 s of recovery - prognostic index), T30 (short-term time-constant of HRR - parasympathetic reactivation marker), rMSSD30s (square root of the mean of the sum of the squares of differences between adjacent R-R intervals on subsequent 30 s segments - parasympathetic reactivation marker), and HRRτ (time constant of the first order exponential fitting of HRR - marker of sympathetic withdraw and parasympathetic reactivation) were measured. Paired t-test and two-way ANOVA were used. HRR60s and HRRτ were similar after exercise in the morning and evening (27 ± 7 vs. 29 ± 7 bpm, p = 0.111, and 79 ± 14 vs. 96 ± 29 s, p = 0.119, respectively). T30 was significantly greater after evening exercise (405 ± 215 vs. 295 ± 119 s, p = 0.002) and rMSSD30s was lower in the evening (main factor session, p = 0.009). In conclusion, in pre-hypertensive men, the prognostic index of HRR, HRR60s, is not affected by the time of day when exercise is conducted. However, post-exercise parasympathetic reactivation, evaluated by T30 and rMSSD30s, is blunted after evening exercise.
authors.affiliation: a Exercise Hemodynamic Laboratory, School of Physical Education and Sport , University of São Paulo , São Paulo , Brazil .
authors.forename: Leandro
authors.initials: L
authors.lastname: Brito
authors.affiliation: a Exercise Hemodynamic Laboratory, School of Physical Education and Sport , University of São Paulo , São Paulo , Brazil .
authors.forename: Tiago
authors.initials: T
authors.lastname: Peçanha
authors.affiliation: b Post-graduate Program of Medicine, University of 9 July , São Paulo , Brazil , and.|c Department of Nephrology , Medical School, University of São Paulo , São Paulo , Brazil.
authors.forename: Taís
authors.initials: T
authors.lastname: Tinucci
authors.affiliation: a Exercise Hemodynamic Laboratory, School of Physical Education and Sport , University of São Paulo , São Paulo , Brazil .
authors.forename: Natan
authors.initials: N
authors.lastname: Silva-Junior
authors.affiliation: a Exercise Hemodynamic Laboratory, School of Physical Education and Sport , University of São Paulo , São Paulo , Brazil .
authors.forename: Luiz
authors.initials: L
authors.lastname: Costa
authors.affiliation: a Exercise Hemodynamic Laboratory, School of Physical Education and Sport , University of São Paulo , São Paulo , Brazil .
authors.forename: Claudia
authors.initials: C
authors.lastname: Forjaz
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D058246:Prehypertension / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: Circadian rhythm; aerobic exercise; cardiac autonomic modulation; diurnal variation; parasympathetic reactivation