Deepak Sharma et al / International Journal of Biomedical Research 2015; 6(09): 641-646. 641 IJBR (2015) 6 (09) www.ssjournals.com International Journal of Biomedical Research ISSN: 0976-9633 (Online); 2455-0566 (Print) Journal DOI: 10.7439/ijbr CODEN: IJBRFA Original Research Article Time domain and frequency domain analysis of heart rate variability in elite Nepalese football players Deepak Sharma *1 , Bishnu Hari Paudel 2 , Rita Khadka 2 , Dilip Thakur 2 , Niraj Khatri Sapkota 1 , Dev Kumar Shah 1 , Santosh Deo 3 , Md Nazrul Islam 1 1 Department of Physiology, Chitwan Medical College, Bharatpur, Chitwan, Nepal 2 Department of Physiology, BP Koirala Institute of Health Sciences, Dharan, Nepal 3 Department of Physiology, Birat Medical College, Biratnagar, Nepal *Correspondence Info: Dr. Deepak Sharma Chitwan Medical College Chitwan, Nepal E-mail: drdeepakphysiology@gmail.com Abstract Objective: There are conflicting reports in the literature concerning the time and frequency domain parameters of heart rate variability (HRV) in athletes. Furthermore, the exact impact of different sports disciplines on cardiac autonomic function is unclear. Thus, the study was destined to assess and compare HRV in the time and frequency domains between elite Nepalese football players and non-athletes. Methods: Temporal and spectral HRV parameters determined from 5-minute continuous ECG during supine rest were studied in 27 elite male football players (age: 22.74±2.52 years) with excellent cardiorespiratory fitness, and 30 non-athletic male (age: 23.41±2.95 years) volunteers (control group). All HRV parameters were compared between the groups. Results: Resting heart rate, systolic and diastolic blood pressure were significantly lower and all parasympathetic-related time and frequency domain indices, including root mean square of successive differences [RMSSD, 55.10(39.40-82.60) vs 25.70(20.10-44.45) ms, p=0.001], High frequency power in absolute value [HF, 1019(582-2127) vs 277(105.50-695) ms 2 , p=0.001] and in normalized unit [HFnu, 57.70(49.50-68.60) vs 42.20 (29.45-56.40)%, p=0.001]), were higher in footballers compared to non-athletics. Similarly, standard deviation of all NN intervals (SDNN), determinant of global HRV, was higher in players (p=0.003). Furthermore, the power spectral components low frequency in normalized unit (LFnu), a sympathetic marker, and LF/HF, which reflect sympatho-vagal balance, were significantly lower in players. Conclusion: The footballers had enhanced parasympathetic (higher RMSSD, HF and HFnu, and lower LF/HF ratio) and diminished sympathetic (lower LFnu) tone on heart. Football playing has favorable effect on the cardiac autonomic profile as indicated by high global HRV (higher SDNN). Keywords: Time and frequency domain, heart rate variability, football players. 1. Introduction Heart rate variability (HRV) is a term used to describe the variations in consecutive R-R intervals or instantaneous heart rate. R-R interval refers to the duration between two adjacent R-wave peaks of normal QRS complex on standard electrocardiogram (ECG) [1]. The rhythm of the heart is controlled by the sino-atrial (SA) node, which is under the influence of sympathetic and parasympathetic branches of the autonomic nervous system. Continuous modulation of pacemaker by these autonomic branches results variations in instantaneous heart rate or consecutive R-R intervals [2]. These variations are analyzed by heart rate variability (HRV), which is considered as a powerful non-invasive tool for the estimation of cardiac autonomic modulations [3,4]. The variations are calculated in the time and frequency domains; in this last condition they are expressed as sine wave power values (power spectrum) [1,5]. Several cross-sectional studies that have compared resting HRV between endurance-trained and untrained subjects have demonstrated inconclusive results. Some have shown that endurance-trained subjects present higher values of power spectral HRV, indicating increasing vagal activity [6,7]; others have reported higher values of the LF component of HRV suggesting higher sympathetic activity [8]. Lower levels of sympathetic