Comparative Analysis of Heart Rate Variability in Athletes and Sedentary Adults

Thesis Abstract

This study investigates the differences in heart rate variability (HRV) between athletes and sedentary adults, addressing the growing concern over the influence of physical activity levels on autonomic nervous system regulation and cardiovascular health. Recognizing the significance of HRV as a non-invasive biomarker for autonomic function and overall cardiovascular resilience, the research aims to delineate the extent to which regular athletic training modulates HRV parameters in comparison to a sedentary lifestyle. The specific objectives of the study include (1) quantifying and comparing time-domain, frequency-domain, and nonlinear HRV measures in both cohorts; (2) exploring the association between HRV indices and physical activity levels; and (3) examining potential gender and age-related differences within and between groups. The research adopts a cross-sectional comparative design grounded in the transactional model of autonomic regulation, emphasizing the dynamic interplay between sympathetic and parasympathetic influences. The study population comprises 200 adults aged 20-40 years, equally divided into athletic and sedentary groups, recruited through stratified random sampling from local sports clubs and community centers. Sample size was calculated based on power analysis to detect a minimum effect size of 0.5 with 80% power at a 0.05 significance level, ensuring statistical robustness. Data collection employed 24-hour Holter electrocardiogram (ECG) monitoring, supplemented by structured questionnaires assessing physical activity frequency, intensity, and duration, validated through prior pilot testing. HRV analysis involved extracting standard parameters such as SDNN, RMSSD, LF power, HF power, and LF/HF ratio, using Kubios HRV software. To ensure instrument validity and reliability, calibration procedures were conducted, and inter-observer reliability was assessed via duplicate analyses on a subset of recordings, yielding intraclass correlation coefficients exceeding 0.85. Descriptive statistics characterized the sample, while inferential analyses included independent samples t-tests and ANOVA to compare HRV metrics between groups, with multiple linear regression models examining predictors of HRV indices while controlling for confounders like age, gender, and BMI. Additionally, multivariate analysis of covariance (MANCOVA) was employed to assess group differences across multiple HRV variables simultaneously. It is hypothesized that athletes will demonstrate significantly higher HRV measures indicating enhanced parasympathetic activity compared to sedentary adults, with notable differences in SDNN, RMSSD, and HF power. The study anticipates finding positive correlations between physical activity levels and HRV parameters, supporting the concept that regular endurance or strength training enhances autonomic tone. The approved models will elucidate the extent of these relationships, and subgroup analyses are expected to reveal gender and age moderating effects. Expected findings will contribute to the growing body of evidence linking physical activity with improved autonomic cardiovascular regulation and may offer normative HRV benchmarks for different activity levels within young adult populations. The research advances theoretical understanding by integrating the neurocardiac regulation framework with empirical data, facilitating a nuanced interpretation of HRV as an objective marker of fitness and health. The study concludes that regular physical activity positively influences HRV, emphasizing the importance of exercise in promoting autonomic balance and cardiovascular health. Based on the findings, it is recommended that health practitioners incorporate HRV assessment into routine screenings and encourage structured exercise programs tailored to optimize autonomic function. The research also suggests avenues for subsequent longitudinal and intervention studies to explore causality and the potential mediating role of psychological factors in modulating HRV responses to physical activity.