Reliability and Effect of Submaximal Aerobic Exercise Test to Assess Cardiac Autonomic Response in Female Normotensive Offspring of Hypertensive Parents

ABSTRACT

Background: In recent past researches have shown genetic inheritance is an important predisposing factorfor future development of hypertension in normotensive offspring of hypertensive parents (NOHP). Heightenedcardiacautonomic reactivity to mental and physical stress has been reported in these population in recentpast. Exercise is a physiological stressor commonly used to elicit occult cardiovascular abnormalities thatare not detected at rest. Compare to maximal, supramaximal and high intensity chronic exercise, singlebout of submaximal aerobic exercise that can also potentially evoke cardiac autonomic response even atdelayed phase of recovery state has been given little attention till date. There is also paucity of dataregarding effect of aerobic exercise test particularly on young female NOHP at recovery period.Objective: The aim of this study was to evaluate the reliability and effect of single bout of submaximalaerobic exercise test to assess the cardiac autonomic response in young female NOHP.Materials And Method: An observation and cross-sectional study was conducted at autonomic functionresearch laboratory of Physiology department at R G Kar Medical College, Kolkata between March 2016 andFebruary 2017 on 50 young healthy female subjects aged 18-25 years and divided them in two groupsnormotensive offspring of hypertensive (NOHP) and normotensive offspring of normotensive parents (NONP)in 11 ratio. Resting blood pressure (BP) was recorded first manually. After that short-term heart rate variability (HRV) test for five minutes conducted by a multiple-channel Polyrite-D instrument for five minutesin supine position at rest and last five minutes of 15 minutes recovery phase after a single bout of submaximal(50% VO2max) aerobic exercise using treadmill machine and following modified Black-Bruce protocol as wellas Astrand-Rhyming nomogram. Data was analysed in frequency domains of HRV using spectral componentslike heart rate [HR], low frequency at normalised unit [LFnu], high frequency at normalised unit [HFnu], LF/HF ratio and total power [TP].Results: Spectral components of HRV had shown exaggerated sympathetic excitation (mean LFnubasal57.14±12.313, mean LFnurecovery 66.403±12.471, p value 0.0012, t value 3.686), attenuated parasympatheticmodulation (mean HFnubasal 42.839±12.217, mean HFnurecovery 32.224±12.335, p value <0.0001, t value5.585) and overall sympathovagal imbalance (SVI) (mean LF/HFbasal 1.559±0.858, mean LF/HFrecovery2.378±0.925, p value <0.0001, t value 5.788) in NOHP only at recovery phase but not in NONP. Moreover,post exercise frequency domain HRV analysis had shown significant difference between the two groups,higher mean values of LFnu, LF/HF ratio and lower HFnu as well as attenuated TP were observed amongNOHP compared to NONP.Conclusion: Study indicated that exercise at 50% of VO2max was reliable to implement a sub-maximal loadto evoke substantial cardiac autonomic response and apparently healthy young female NOHP exhibit impairedautonomic modulation which could lead to develop hypertension in future.