Pagaduan, J.C. et al.: Heart rate variability of obese and non‐obese Filipino... Acta Kinesiologica 7 (2013) 2: 85‐90 85 HEART RATE VARIABILITY OF OBESE AND NON-OBESE FILIPINO ADOLESCENTS Jeffrey C. Pagaduan 1 , Vish Unnithan 2 and John Erskine 2 1 College of Human Kinetics, University of the Philippines – Diliman, Philippines 2 Faculty of Health Sciences, Staffordshire University, U.K. Original scientific paper Abstract The purpose of this research was to compare the differences in heart rate variability (HRV) parameters between obese and non-obese individuals from spontaneous breathing (SB) and paced breathing (PB). Totally 20 subjects, healthy male adolescents participated in the study: 10 obese (age: 17.1 ± 0.74 yrs; height: 173.5 ± 4.94 cm; weight: 103.9 ± 16.4 kg; %BF =29.0 ± 5.68; waist circumference (WC): 102.8 ± 7.8 cm; systolic blood pressure (SBP): 119.2 ± 5.9 mmHg; diastolic blood pressure (DBP): 74.6 ± 6.7; physical activity level: 36.9 ± 9.48) and 10 non-obese (age:16.5 ± 0.71 yrs; height: 166.7 ± 5.33 cm; weight: 55.1 ± 106 kg; %BF:10.5 ± 5.22; SBP: 100.0 ± 11.5 mmHg; WC: 68.3 ± 6.4; DBP: 62.6 ± 6.6; physical activity level: 41.1 ± 14.8) They underwent two 5-minute heart rate recordings for SB and metronome guided PB respectively. PB was adjusted from the respiratory rate during SB. Results from two- way repeated measures ANOVA revealed non-significant differences in the standard deviation of N-N intervals (SDNN), low frequency (LF), peak LF (LFpeak), relative contribution of LF (%LF), LF normalized unit (LFnu), high frequency (HF), peak HF (HFpeak), relative contribution of HF (%HF), HF normalized unit (HFnu), total power (TP), LF to HF ratio (LF/HF), instantaneous beat to beat variability (SD1), continuous beat to beat variability (SD2), and SD1 to SD2 ratio (SD1/SD2). In conclusion, metronome guided PB adjusted from SB rate did not produce any significant difference in time, frequency and non-linear domains of HRV between asymptomatic obese and non-obese adolescents. Key words: heart rate variability, obesity, adolescence Introduction In the recent decade, there has been an increasing trend in the use of heart rate variability (HRV) as tool for measuring autonomic functioning in clinical and sport settings. HRV refers to the R-R interval between consecutive heart rates which can be measured from cardiac electrical activity (Gamelin et al., 2006; Task Force, 1996). Indices of HRV include time, frequency and non-linear values. For time domain, the standard deviation of normal to normal (NN) intervals (SDNN), triangular index, standard deviation of sequential 5-minute period mean values of NN intervals (SDANN), the square root of the mean squared differences between successive RR intervals (RMSSD) are recommended for HRV assessment (Task force, 1996). SDNN and triangular index are estimates of overall HRV. SDANN and RMSSD estimate long-term and short-term components of HRV respectively. In the frequency domain, low frequency (LF), high frequency (HF), and LF/HF ratio are values that detect vagal activity. Low frequency is also known as the 10-second rhythm or the Mayer wave which range from 0.04 to 0.15 Hz. Researchers suggest that LF is a measure of sympathetic activity (Malliani et al., 1991). High frequency (HF) range from 0.15 to 0.4 Hz and is believed to reflect parasympathetic activity (Task force, 1996). LF/HF ratio is suggested to mirror sympathovagal balance or sympathetic activity. Recently, there has been an increasing interest in the use of non-linear methods in HRV analysis (Sunkaria, 2011). These non-linear parameters are Poincaré plot values which are represented by SD1, SD2, and SD1 / SD2 (Brunetto et al., 2005; Silva et al., 2005; Vanderlei et al., 2010). SD1 represents an index of instantaneous recording of the variability of beat-to-beat and reflects parasympathetic activity. On the other hand, SD2 is the HRV in the long term-records and represents overall HRV. SD1/SD2 is the ratio between short and long variations of RR intervals. Adjustment of respiratory rate plays a crucial role in HRV (Guzik et al., 2007; Millis et al., 2011; Millis et al., 2010; Schipke et al., 1999; Song & Lehrer, 2003). For example, Millis et al. (2011) found out that TP, SDNN, VLF and LF/HF were lower in spontaneous breathing (SB) compared to paced breathing (PB) at 12 breaths/min (0.2 Hz) in healthy males. Millis et al. (2010) also discovered lower normalized LF in SB (0.2 Hz) compared to PB among healthy young men. Guzik et al. (2007) demonstrated that 0.2 Hz breathing temporarily increases HF and reduces long term HRV. Song and Lehrer (2003) suggested that slow breathing rates produced higher HRV amplitudes than faster breathing rate. Lastly, Schipke et al. (1999) found no significant differences in HRV time domains at various respiratory rates. In adolescent obesity, conflicting results comparing HRV parameters of obese and non-obese adolescents exist. Guízar et al. (2005) identified that male obese adolescents posted higher LF/HF index but lower SDNN and total power (TP) compared to their non-obese counterparts. Khrisanapant et al., (2008) discovered no significant differences in sympathetic and parasympathetic functioning between obese (OB) and non-obese (NO) male and female adolescents.