ORIGINAL ARTICLE Long-term exercise training improves autonomic nervous system profile in professional runners

Abstract

Introduction: Moderate-intensity endurance training causes increased parasympathetic activity while very intensive (extreme) exercise loads may lead to persistently elevated sympathetic tone in champion class athletes preparing for competitions. Exercise training loads used by regional class sportsmen are usually somewhat less intensive. Aim: To assess the changes in autonomic nervous system activity in a group of regional class runners during a long-term training cycle preparing them for competitions. Methods: Twenty-four regional class runners (including 22 males) with a mean age of 24±4 years (18 to 34 years) were enrolled in the study. Resting heart rate (mean HR) and autonomic system tone were assessed in the final period of the preparatory training (1) and in the terminal phase of the competition period (2). Additionally, ten-minute long continuous non-invasive acquisitions of systolic arterial blood pressure – SAP (Finapress, Ohmeda) and heart rate period – HP (Mingograf 72^oC) were carried out in each subject. Then arterial baroreflex sensitivity by means of spectral analysis (BRS_WBA) and indices of heart rate variability (SDNN, pNN50, RMSSD, TP, LF, LFnu, HF, LF/HF) were calculated from the recorded SAP and HP signals. Results: A statistically significant increase in indices of heart rate variability such as BRS_WBA, SDNN, pNN50, TP and LF in period 2 when compared with period 1 was found. Their values were 17.2±8.2 vs 11.5±5.1 ms/mmHg (p=0.0001), 91±55 vs 70±36 ms (p=0.0002), 48±24 vs 38±23% (p=0.03), 4364±2614 vs 3384±2298 ms² (p=0.01), 2262±2031 vs 1398±1203 ms² (p=0.002), respectively. Borderline elevation of the RMSSD index (83±62 and 67±37 ms respectively for period 1 and period 2; p=0.09) was also noted. The other calculated parameters did not differ significantly. Conclusions: Long-term intensive exercise training, employed by regional class runners preparing for competitions, changes the autonomic profile, promoting parasympathetic dominance. This may be an important argument to encourage many young and healthy people to engage in endurance sports at such intensity.