Effect of Isometric Exercise on Heart Rate Variability in Prehypertensive Young Adults

Abstract

Background and Objective: Heart rate variability (HRV) is a sensitive and specific non-invasive tool to evaluate the degree of heart rate variation under the balanced influence of sympathetic and parasympathetic components of the cardiac autonomic nervous system. The aim was to study the effect of isometric hand grip exercise on HRV in prehypertensive young adults and to find a correlation of HRV with body mass index (BMI). Materials and Methods: This observational study was done on 60 healthy young adults aged 18–30 years. All the subjects were divided into three groups of 20 each on the level of their BMI and systolic and diastolic blood pressures. Group I were subjects with BMI <25 and normotensive, group II with BMI <25 and prehypertensive, and group III with BMI >25 and prehypertensive. HRV analysis (Chart HRV module, ADInstruments Pty Ltd) was performed with the following parameters calculated: low-frequency power (LF), high-frequency power (HF), and LF/HF ratio. Results: LF/HF ratio was significantly increased (P<0.001) in prehypertensive subjects (groups II and III) when compared with the normotensive subjects (group I), which indicates a heightened sympathetic discharge in prehypertensives. A positive correlation between anthropometric parameters and cardiac autonomic activity parameters and increased sympathetic activity in obese subjects were noted. Conclusion: An increase in anthropometric indices is associated with a change in cardiac autonomic activity, especially toward sympathetic activity. Regular anthropometric assessment can prevent the development of cardiac abnormalities and the incidence of sudden cardiac death.