Effects of cigarette smoking on cardiac autonomic function during dynamic exercise

The purpose of this study was to investigate the acute effect of cigarette smoking on cardiac autonomic function in young adult smokers during dynamic exercise. Fourteen healthy young smokers (21.4±3.4 years) performed peak and submaximal exercise protocols under control and smoking conditions. Resting and submaximal beat-to-beat R-R series were recorded and spectrally decomposed using the fast Fourier transformation. Smoking resulted in a significant decrease in work time, V̇O_2peak and peak O₂ pulse (P<0.05). Heart rate increased at rest and during submaximal exercise after smoking (P<0.05). The raw high frequency and low frequency power were significantly reduced by smoking, both at rest and during exercise (P<0.05). The low to high frequency ratio was higher after smoking (P<0.05). The normalised low frequency power was also significantly increased by smoking, but only at rest (P<0.05). These data demonstrate that the tachycardic effect elicited by smoking is accompanied by acute changes in heart rate spectral components both at rest and during exercise. Therefore, the cardiac autonomic control is altered by smoking not only at rest, but also during exercise, resulting in reduced vagal modulation and increased sympathetic dominance.