Effect of moderate physical exercise on noninvasive cardiac autonomic tests in healthy volunteers

Background: In addition to the assessment of extreme cardiovascular reserve, new methodology is needed which is sensitive enough to detect subtle improvement in cardiovascular fitness in cardiac patients. Aim: This study modelled subtle clinical improvement by a moderate physical activity programme in healthy volunteers and investigated whether the improved fitness is detectable by non-invasive tests of cardiac autonomic status. Methods: Twenty healthy volunteers (ten women, mean age 39.6±7.8 years) were divided into two groups of five women and five men in each. One group (the active group) was subjected to a moderate physical training programme for 6 months. The other group (the passive group) served as controls and continued with a predominantly sedentary lifestyle. Twice before commencing the exercise programme and regularly afterwards, subjects were investigated by a series of non-invasive autonomic tests including controlled respiration, active postural change, isometric handgrip, and Valsalva manoeuvre. A continuous three lead semi-orthogonal electrocardiogram and continuous blood pressure monitoring was obtained. Statistical descriptors of heart rate and blood pressure, spectral descriptors of their modulation, and baroreflex index giving the proportion between simultaneous heart rate and blood pressure changes were obtained from each test. Results: Although the exercise programme was not extensive enough to be detected in changes of the baseline heart rate, the minimum RR interval during the Valsalva manoeuvre prolonged significantly with exercise in the active group. The mean arterial diastolic pressure decreased significantly. High frequency components of RR interval modulations decreased in supine controlled respiration and increased in standing controlled respiration and a trend towards an increase of both high frequency and low frequency components of diastolic arterial pressure modulations was noted with exercise. Baroreflex index assessed from Valsalva manoeuvre increased significantly. Conclusion: The study suggests that a selected set of non-invasive autonomic tests is sensitive enough to depict moderate improvement in cardiovascular fitness and that a multivariate assessment of cardiovascular fitness based on these tests might be applicable to monitoring chronic cardiac patients subjected to different clinical management modes.