Introduction:

The autonomic nervous system plays an important role in cardiovascular readjustments to exercise. In cardiovascular hyperreactivity there is a greater sensitivity of the sympathetic system to different stressors.

Objective:

To determine the characteristics of cardiac autonomic control in young adults with different degrees of cardiovascular reactivity under basal conditions and during isometric exercise.

Method:

The sample consisted of 97 individuals of both sexes, and was divided into three groups: normoreactive, hyperreactive and with hypertensive response, according to the pressor response to weight-bearing tests. The individuals underwent a complete study of heart rate variability at rest and during isometric test. The frequency domain for the variables was: low, high, low/high resting ratio, and the parameters of Poincaré plots at rest and during exercise (values of standard deviation 1 [SD1], 2 [SD2], and the reason between them).

Results:

Under basal conditions, hyperreactive individuals with a hypertensive response had a sympathetic predominance over cardiac function and lower heart rate variability. During the isometric exercise SD1 and SD2 axes values decreased in all groups and SD1/SD2 ratio decreased in normoreactive individuals with hypertensive response; but it was hardly modified in those hyper-reactive.

Conclusions:

Individuals with cardiovascular hyperreactivity have a prior autonomic imbalance under basal conditions and a reduction of autonomic vagal modulation during exercise that may favor the development of arterial hypertension.

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