Heart rate variability during incremental cycling exercise in healthy untrained young men.Folia Med Cracov. 2004; 45(1-2):3-12.FM
Linear relationship between the increase of heart rate (HR) and the power output (PO) during sub-maximal exercise is well documented. However the study considering the effect of progressive increase of PO on the parameters of heart rate variability (HRV) remain scarce.
This study investigated changes of the HRV time and spectral parameters in young, untrained men during incremental cycling exercise.
Fifteen young, untrained men aged 21 +/- 1.5 years participated in our study. Preliminary medical examination excluded any cardiovascular diseases. The examined individuals were cycling on the cycle ergometer (Monark 824E, Sweden) with constant frequency, amounting to 60 rev x min(-1). PO was increased by 30 W every 3 minutes. ECG was recorded via shortened limb lead I, using Dual BIO Amp (AD Instruments, Castle Hill, Australia) hardware and Power Lab (AD Instruments) software. Spectral analysis of HRV was based on the fast Fourier transformation (FFT). The time (HR, RMSSD) and spectral (LF, HF) parameters were analysed within 3 minutes time periods, before the exercise and on each level of the generated power output.
The exercise was performed until the subjects reached 80% of the HR max expected for their age. This has occurred at the PO = 202 +/- 33 W (mean +/- SD). Mean HR in this group showed linear increase (p < 0.001) with power output (90 +/- 7 bt x min(-1) at 30 W vs. 166 +/- 11 bt x min(-1) at the power output of 202 +/- 33 W). Significant decrease of time parameters of the HRV (0 W vs. 202 +/- 33 W)--SDNN (p < 0.001) and RMSSD (p < 0.001) were observed in the analysed group. Spectral parameters of the HRV also presented significant reduction. Decreases of total power of the HRV spectrum (TP, p < 0.001), low frequency (LF, p < 0.01) and high frequency (HF, p < 0.01)) spectra as well as LF/HF ratio (p < 0.01) were noted.
In the light of the present study, the applicability of the HRV power spectrum, with its present interpretation, to the assessment of the sympatho-vagal interaction during incremental exercise is indeed very questionable.