The changes of heart rate variability in response to deep breathing in professional swimmers.

INTRODUCTION: The analysis of heart rate variability (HRV) is a useful tool for the evaluation of adaptation processes of autonomic nervous system (ANS) to physical exercise. The deep breathing test (DB) induces the increased activity of the parasympathetic component of ANS. The aim of the study was to evaluate the influence of DB on ANS activity in professional swimmers and non-trained persons.

METHODS: The study included 10 healthy swimmers (5 women and 5 men, mean age 21 ± 2 yrs) in the transitory phase of their training cycle, and a control group comprising 31 healthy volunteers. The evaluation of ANS activity was based on the time and frequency domain indices of HRV determined at rest and during DB.

RESULTS: Compared to the controls, swimmers were characterized by significantly higher values of the following HRV indices determined at rest: mRR (902.9 ± 102.5 ms vs. 744 ± 67.5 ms, p <0.05), rMSSD (71.4 ± 46.9 ms vs. 41.3 ± 20.7 ms, p <0.05), pNN50 (28.3 ± 17.4% vs.14 ± 10.7%, p <0.05), LF (603.5 ± 208.2 ms2 vs. 445.2 ± 137 ms2, p <0.03). Also during DB test, the values of the following HRV indices of the swimmers were significantly higher than in the controls: mRR (899.2 ± 69.2 ms vs. 766.4 ± 63.6 ms, p <0.05), SDNN (114.1 ± 45.1 ms vs. 79 ± 27.7 ms, p <0.05), rMSDD (81.9 ± 38.2 ms vs. 50.7 ± 27 ms, p <0.05), pNN50 (32.9 ± 14.3 % vs. 20.6 ± 14.6%, p <0.05), TP (1972.7 ± 809.5 ms2 vs. 1329.7 ± 532 ms2, p <0.05), HF (657.1 ± 330.9 ms2 vs. 405.7 ± 217 ms2, p <0.05), LF (753.3 ± 294 ms2 vs. 533 ± 213.4 ms2, p <0.05). The analysis of value relative DB-induced changes in time and frequency domain HRV indices revealed significant intergroup differences in reaction to parasympathetic stimulation.

CONCLUSIONS: Based on the results presented in this study, the swimmers' response to deep breathing seems stronger than in persons without professional training. The deep breathing test may be a useful tool to evaluate the dynamic changes in the parasympathetic activity of ANS of sportspersons.