1999 Volume 48 Issue 4 Pages 467-475
It has been shown that the time constant of heart rate decline for the first 30 sec (T30) after exercise, at an intensity lower than the ventilatory threshold (VT), can serve as a specific index to assess post-exercise vagal reactivation. The purpose of this study was to validate the use of a simpler alternative index, i. e. %Δ HR30 (the ratio of heart rate decrement for the first 30 sec after exercise) for the evaluation of parasympathetic nervous reactivation, and to examine whether it would be a useful index in the conditioning of athletes. Eighteen college students performed 4 minutes cycle ergometer exercise routines at intensities of 40%, 80%, and 120% VT to compare the %Δ HR30 and the T30. In addition, the %Δ HR30 was obtained by a field test (4 minutes jogging) in 15 college middle and long distance runners, every morning during summer camp training to assess the state of athletic conditioning. The %Δ HR30 at 80% VT was similar to the value at 40% VT, but significantly different from the value at 120% VT, as was the T30 at 80% VT.
The %Δ HR30 significantly correlated with the T30 and VO2max. During the camp, the %Δ HR30 was higher on mornings following light training days than on mornings following hard training days. These results suggest that the %Δ HR30, at an exercise intensity lower than the VT, could be a simple and useful index to evaluate post-exercise parasympathetic nervous reactivation in the conditioning of athletes.