Different functional exercise orders induce similar acute cardiac autonomic modulation responses in healthy adults: A randomized controlled crossover study

Objectives. - A single session of high-intensity exercise promotes exaggerated increases in sympathetic cardiac activity, which may increase the risk of acute cardiovascular events. However, it is not clear if similar responses occur after an FT session. Thus, this study aimed to: (1) analyze the acute autonomic responses to a single FT session in healthy adults; and (2) compare the autonomic responses to two different orders of exercise during a FT session. Equipment and methods. - Twenty participants completed three experimental sessions in a random order: no exercise/control (C) or FT with different exercise orders (FT1 and FT2). The FT bout consisted of four phases including warm-up, two phases neuromuscular and another with high-intensity interval training. Linear [time-mean RR intervals and standard deviation of all RR intervals (SDNN)-and frequency domains-low frequency (LF) and high frequency (HF)] and non-linear parameters [Poincare index (SD1/SD2 ratio) and Sample Entropy (SampEn)] of heart rate variability were collected before and 60-minutes after the experimental sessions. Data were analyzed by ANOVA with significance achieved at P < 0.05. Results. - Compared to the pre-exercise, RR Interval, SDNN, HF and SampEn decreased and LF and SD2/SD1 increased until 60 minutes after FT1 and FT2 (P < 0.05), while no change was found following C session (P > 0.05). Thus, in both FT sessions, all aforementioned parameters were different compared to the same post-exercise time point in the C session (P < 0.05). No differences were found between FT1 and FT2 (P > 0.05). (c) 2022 Elsevier Masson SAS. All rights reserved.