Impact of Moderate Exercise on Frequency Domain Measures of Heart Rate Variability in Different Body Postures Among Young Healthy Adults

Introduction: Heart rate variability (HRV) is a non-invasive measure of variations in intervals between successive sinus beats, reflecting the dynamic interaction between sympathetic and parasympathetic branches of the autonomic nervous system (ANS). It is useful for assessing autonomic regulation, monitoring responses to exercise, and evaluating cardiovascular risk. Aims and Objectives: To examine changes in HRV parameters in young, healthy male adults before and after moderate-intensity exercise in standing, sitting, and supine postures, with particular emphasis on frequency-domain components and recovery towards baseline. Materials and Methods: This observational study included 25 apparently healthy young men without known metabolic or cardiovascular conditions. ECG recordings were obtained, and HRV was analysed using frequency-domain techniques in standing, sitting, and supine positions before and after moderate-intensity exercise. Post-exercise measurements were recorded following a five-minute recovery period in each posture. Results: HRV responses varied by posture. VLF power decreased in sitting and supine positions but increased in standing. LF power and VLF percentage decreased in standing and sitting, while HF power varied across positions. The LF/HF ratio decreased in all three postures, indicating altered sympathovagal balance during early recovery. Conclusion: HRV reflects cardiac autonomic regulation and exercise responses. Moderate exercise alters HRV parameters depending on body posture, with changes persisting after five minutes of recovery. These findings highlight the importance of posture and recovery duration in autonomic assessment. Keywords: Heart Rate Variability, Exercise, Postures, High Frequency, Low Frequency