Reliability of Symbolic Analysis of Heart Rate Variability and Its Changes During Sympathetic Stimulation in Elite Modern Pentathlon Athletes: A Pilot Study

Jakub S Gąsior; Maciej Rosoł; Marcel Młyńczak; Andrew A Flatt; Bartosz Hoffmann; Rafał Baranowski; Bożena Werner

doi:10.3389/fphys.2022.829887

Reliability of Symbolic Analysis of Heart Rate Variability and Its Changes During Sympathetic Stimulation in Elite Modern Pentathlon Athletes: A Pilot Study

Front Physiol. 2022 Feb 28:13:829887. doi: 10.3389/fphys.2022.829887. eCollection 2022.

Authors

Jakub S Gąsior¹, Maciej Rosoł², Marcel Młyńczak², Andrew A Flatt³, Bartosz Hoffmann⁴, Rafał Baranowski⁵, Bożena Werner¹

Affiliations

¹ Department of Pediatric Cardiology and General Pediatrics, Medical University of Warsaw, Warsaw, Poland.
² Faculty of Mechatronics, Institute of Metrology and Biomedical Engineering, Warsaw University of Technology, Warsaw, Poland.
³ Biodynamics and Human Performance Center, Department of Health Sciences and Kinesiology, Georgia Southern University (Armstrong Campus), Savannah, GA, United States.
⁴ Physiotherapy Division, Faculty of Medical Sciences, Medical University of Warsaw, Warsaw, Poland.
⁵ Department of Heart Rhythm Disorders, National Institute of Cardiology, Warsaw, Poland.

Abstract

Background and purpose: Most studies on heart rate variability (HRV) in professional athletes concerned linear, time-, and frequency-domain indices, and there is lack of studies on non-linear parameters in this group. The study aimed to determine the inter-day reliability, and group-related and individual changes of short-term symbolic dynamics (SymDyn) measures during sympathetic nervous system activity (SNSa) stimulation among elite modern pentathletes.

Methods: Short-term electrocardiographic recordings were performed in stable measurement conditions with a 7-day interval between tests. SNSa stimulation via isometric handgrip strength test was conducted on the second day of study. The occurrence rate of patterns without variations (0V), with one variation (1V), two like (2LV), and two unlike variations (2UV) obtained using three approaches (the Max-min, the σ, and the Equal-probability methods) were analyzed. Relative and absolute reliability were evaluated.

Results: All SymDyn indices obtained using the Max-min method, 0V, and 2UV obtained using the σ method, 2UV obtained using the Equal-probability method presented acceptable inter-day reliability (the intraclass correlation coefficient between .91 and .99, Cohen's d between -.08 and .10, the within-subject coefficient of variation between 4% and 22%). 2LV, 2UV, and 0V obtained using the Max-min and σ methods significantly decreased and increased, respectively, during SNSa stimulation-such changes were noted for all athletes. There was no significant association between differences in SymDyn parameters and respiratory rate in stable conditions and while comparing stable conditions and SNSa stimulation.

Conclusion: SymDyn indices may be used as reliable non-respiratory-associated parameters in laboratory settings to detect autonomic nervous system (ANS) activity modulations in elite endurance athletes. These findings provide a potential solution for addressing the confounding influence of respiration frequency on HRV-derived inferences of cardiac autonomic function. For this reason, SymDyn may prove to be preferable for field-based monitoring where measurements are unsupervised.

Keywords: athletes; heart rate variability; modern pentathlon athletes; non-linear; symbolic dynamics.