Effect of exercise in healthy men on QRS power spectrum

The effect of exercise on the QRS power spectrum has not been evaluated. We hypothesized that increased conduction velocity with exercise might selectively increase high-frequency QRS potentials. Using a digital electrocardiograph (ECG) cart, a single bipolar chest lead was recorded in 21 healthy adult males at rest and then immediately after treadmill exercise. Fast Fourier transform analysis of the ECGs was performed using a 128-ms sampling window, including the QRS but not the P wave. Step discontinuities between PR and ST segments were minimized using a linear correction function to obviate artifactual increases in high-frequency content after exercise. The power spectrum plots of rest and exercise data showed an increase in the amplitude of high frequencies that could not be accounted for on the basis of noise contamination. For the frequency band between 187.5 and 250 Hz, the root-mean-square (RSM) voltage of exercise QRS complexes (10.0 +/- 3.6 micro V) was significantly (P less than 0.02) greater than that of rest QRS complexes (7.8 +/- 1.2). However, base-line noise level (computed over a 32-ms interval during the ST segment) was not different between rest and exercise over this high-frequency band. The same exercise protocol was also applied in 11 normal male subjects using an analog ECG cart. For the 187.5- to 250-Hz band, the RMS voltage of the QRS after exercise (13.0 +/- 1.8 micro V) was also significantly (P less than 0.01) greater than at rest (10.2 +/- 2.8) without any difference in ST segment noise level over the same frequency range. These data indicate that exercise causes an increase in the amplitude of high-frequency QRS potentials in healthy men.