Abstract

Rapid heart rate (HR) changes take place at the onset and at the end of exercise. The aim of this study was to analyze these changes at different exercise levels. A total of 17 healthy men, who without being told the aim of the study pedaled an electrically braked bicycle at 60 rpm ON transients, were studied during changes in work rates from 0 to 1, from 1 to 2, and from 2 to 4 W/kg. OFF transients were measured from 4 and from maximal work rate to 0 W/kg. The ECG was recorded starting from 5 s before until 15 s after each work rate change. Of the ON transients only the 2nd and 3rd suggested differences, while the the OFF transients did not differ significantly. All of the transients were reproducible for a given subject. The parasympathetic blockade performed in two subjects produced slower transients (except for the 1st ON). No correlation was found between the transients and V02max. In conclusion, within 15 s, the ON and OFF transients showed changes of 10 and 5, respectively, in HR. They were primarily mediated by the vagus. The transients reported here are slower than those found by others, and this probably reflects the lack of anticipation by the subjects or previous inactivation of the joint receptors, due to the fact that the ON transients were always measured during cycling, starting at 20 W and 60 rpm. Verf.-Referat