Relative roles of the sympathetic and parasympathetic systems in the 4-s exercise test

To evaluate the relative influence of the two branches of the autonomic nervous nervous system on the 4-s exercise test which measures heart rat acceleration at the onset of exercise, 6 healthy male subjects performed the 4-s test under sympathetic blockade with propranolol, parasympathetic blockade with atropine and dual blockade. The magnitude of the 4-s test results (meams ñ SD) was significantly different only between the conditions with and without atropine (1.04 ñ 0.03 vs 1.53 ñ 0.33, respectively), with no differences between the control (1.60 ñ 0.25) and the test under sympathetic blockade (1.51 ñ 0.33). These results support the conclusion that the 4-s exercise test is a specific method for the evaluation of parasympathetic activity

Vagal activity: effect of age, sex and physical activity pattern

Heart rate response to a short (4 s) bicycle exercise test during maximal inspiratory apnea was used to assess vagal activity (VA). This study aims to evaluate the role of age, sex and physical activity pattern on VA. A total of 148 subjects, divided into athletes (N = 90) and non-athletes (N = 58) were tested. No correlation was found between age (range from 15 to 42 years) and VA in the male and female athletes (P>0.05). No gender effect could be identified. In spite of a slight tendency toward higher VA in athletes, no significant differences could be found between the two groups