title: Absence of parasympathetic reactivation after maximal exercise.
abstract: The ability of the human organism to recover its autonomic balance soon after physical exercise cessation has an important impact on the individual's health status. Although the dynamics of heart rate recovery after maximal exercise has been studied, little is known about heart rate variability after this type of exercise. The aim of this study is to analyse the dynamics of heart rate and heart rate variability recovery after maximal exercise in healthy young men. Fifteen healthy male subjects (21·7 ± 3·4 years; 24·0 ± 2·1 kg m(-2) ) participated in the study. The experimental protocol consisted of an incremental maximal exercise test on a cycle ergometer, until maximal voluntary exhaustion. After the test, recovery R-R intervals were recorded for 5 min. From the absolute differences between peak heart rate values and the heart rate values at 1 and 5 min of the recovery, the heart rate recovery was calculated. Postexercise heart rate variability was analysed from calculations of the SDNN and RMSSD indexes, in 30-s windows (SDNN(30s)  and RMSSD(30s) ) throughout recovery. One and 5 min after maximal exercise cessation, the heart rate recovered 34·7 (±6·6) and 75·5 (±6·1) bpm, respectively. With regard to HRV recovery, while the SDNN(30s)  index had a slight increase, RMSSD(30s)  index remained totally suppressed throughout the recovery, suggesting an absence of vagal modulation reactivation and, possibly, a discrete sympathetic withdrawal. Therefore, it is possible that the main mechanism associated with the fall of HR after maximal exercise is sympathetic withdrawal or a vagal tone restoration without vagal modulation recovery.
authors: Laboratory of Motor Assessment, Faculty of Physical Education and Sports, Federal University of Juiz de Fora, Minas Gerais, Brazil. tiago_faefid@yahoo.com.br
authors: Tiago Peçanha
authors: TP
authors: de Oliveira
authors: Raphael
authors: R
authors: de Alvarenga Mattos
authors: Rhenan Bartels Ferreira
authors: RB
authors: da Silva
authors: Rafael Andrade
authors: RA
authors: Rezende
authors: Jorge Roberto Perrout
authors: JR
authors: de Lima
mesh_terms: D000328:Adult; D015444:Exercise; D005080:Exercise Test; D006321:Heart / Q000294:innervation*; D006339:Heart Rate; D006801:Humans; D008297:Male; D018763:Muscle Fatigue; D010275:Parasympathetic Nervous System / Q000502:physiology*; D020127:Recovery of Function; D013997:Time Factors; D055815:Young Adult