Session S22.1

Effects of Pedaling on the High Frequency Components of HRV during Exercise

F Villa*, P Castiglioni, G Merati, P Mazzoleni, M Di Rienzo

Fondazione Don Gnocchi
Milano, Italy

The existence of a spectral peak at frequency higher than the respiratory frequency in heart rate spectra, during exercise test at the cycloergometer [1], possibly being associated to the pedaling frequency, has been anecdotally reported. Aim of our study was to gather a deeper understanding of this phenomenon. This was done by evaluating four young healthy volunteers (2M/2F, 18-22 yrs) while pedaling on a cycloergometer. On the thorax of each subject, we placed 4 electrodes to derive a standard 3-lead ECG, and 5 passive reflective markers to obtain the respiratory frequency by means of a 7 TV-camera optoelectronic device. The latter device was also used to measure the pedal movement and thus the actual cycling frequency. After 1 min of rest on the cycloergometer, each subject was asked to perform two tests - the first at 60 rpm and the second at 70 rpm pedaling frequencies - with incremental loading (starting at 50W with 25W increment until exhaustion). Whenever a spectral peak synchronous with the pedaling frequency was identified, the subject was asked to breath at a known fixed rate (24 breaths/min paced by a metronome). This avoided a possible interference of respiratory harmonics on the spectral peaks due to pedaling. ECG was sampled at 960 Hz, while the respiratory frequency, thorax and pedal movements were sampled at 60 Hz. Clear spectral peaks at the pedaling frequency were observed in all four subjects at specific loads (around 100W for females and 170W for males). When measured during paced breathing, the power of these pedaling peaks was particularly intense reaching 29% (+11%), M (+SD) of the respiratory peak power. Our study indicates that pedaling actually influences high frequency components of HRV and produces evident spectral peaks synchronous with the pedaling frequency. Since we also observed that the overall displacement of the chest was the same regardless of the work load, we can exclude that these spectral peaks are due to a motion artifact, and we can rather hypothesize that these peaks are related to the muscle pump mechanism.
[1] Bailòn R. et al, Proc. 29th IEEE EMBS Conf., 6674-7; Meste O. et al., Proc. 29th IEEE EMBS Conf., 279-82.

(Abstract Control Number: 161)