Abstract

Study of Heart Rate Variability among Normal and Overweight Individuals during Pre-and Post-Exercise Period

Background: Sympathetic activity in obesity-related cardiovascular diseases indicates the association between cardiac autonomic functions and BMI (Body Mass Index). The Heart Rate Variability (HRV) is considered as an appropriate measure of cardiac autonomic function. A stressor, like an exercise, requires changes in the neural, cardiovascular and autonomic control that are unique to the person. So the study was conducted to assess the heart rate variability of normal and overweight individuals during the pre-and post-exercise period. Methods: A case-control study with 42 subjects of 17-25 years old was done. Subject with their BMI ≥ 25 kg/m2 (overweight) was taken as cases and their BMI within normal limits (18.5 kg/m2-24.9 kg/m2) was taken as controls. Resting HRV was recorded. Then, the subjects were asked to perform Harvard Step Test and the post-exercise HRV was recorded immediately. Results: At rest, the values of HRV domains like High Frequency (HF) and RMSSD and pNN50 (Indicators of parasympathetic activity) were less and the Low Frequency (LF) and LF/HF (Indicators of sympathetic activity) were high in an overweight group compared to control. After exercise, the difference in the HRV variables became more prominent and LF/HF became significant for the overweight group compared to the control group. Correlation between HRV variables and BMI remained almost the same both in pre-and post-exercise. Conclusion: Overweight individuals have their HRV indices indicative of dominant cardiac sympathetic activity and reduced parasympathetic activity in response to simple aerobic exercise compared to individuals with normal BMI. Hence, it is likely that overweight individuals are prone to develop various cardiovascular diseases in their future life.

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