Relationship between Autonomic Functional Status and Maximal Aerobic Capacity

Abstract

Introduction: Modern autonomic function tests can assess the degree and spread of autonomic dysfunction non invasively. Cardiovagal, pseudomotor and adrenergic autonomic functions could be assessed in standard laboratory tests. Cardio-respiratory Fitness (CRF) also known as aerobic fitness or maximal aerobic power is typically reported as VO2 max. Aim: To find the relationship between autonomic functional status and maximal aerobic capacity (VO2 max). Materials and Methods: This observational study was conducted in the Research laboratory of Department of Physiology at RUHS College of Medical Sciences, Jaipur Rajasthan, India, from December 2020 to May 2021. The study included 100 apparently healthy students between 18-25 years of age and not practicing any form of exhaustive physical training (cycling, aerobic, skating, scuba diving, professional sports, track and field, water jogging, walking at 5 mph, competitive gymnasium). Autonomic functional status was assessed by various parasympathetic and sympathetic tests. VO2 max was assessed by treadmill test using Graded exercise protocol. To found a correlation between VO2 max and autonomic function test parameters, Pearson’s Pearson correlation test was done. Results: The subjects had a mean age of 21.03±2.45 years, mean height of 1.64±0.08 m, mean weight of 59.66±11.15 kg and mean Body Mass Index (BMI) of 22.08±3.75 kg/m2. Mean height was 1.69±0.06 metre for male subjects and 1.58±0.06 metre for female subjects; mean weight was 62.52±9.52 kg for male subjects and 56.80±11.64 kg for female subjects. Mean BMI was 21.57±3.06 kg/m2 for male subjects and 22.59±4.3 kg/m2 for female subjects. Weak positive correlations were found between VO2 max and autonomic function test parameters, such as Valsalva ratio and hand grip blood pressure response, whereas weak negative correlations were found between VO2 max and Expiration/Inspiration (E/I) ratio ratio. VO2 max had a weak positive association (r-value=0.024) with Valsalva ratio and Blood pressure response to hand grip test (r-value=0.111), but a weak negative correlation (r-value=-0.019) with E/I ratio in males. Conclusion: Regular aerobic exercise appears to be associated with decrease in sympathetic responses and increase in parasympathetic responses. The present study indicated the existence of gender differences in autonomic function tests in young adults of 18-25 years of age due to difference.

Keywords

• expiration/inspiration ratio
• hand grip test
• valsalva ratio