Functional alterations of vascular endothelial cells may be evaluated by analysing differences in effects of endothelium-dependent [acetylcholine (ACh)] and endothelium-independent [sodium nitroprusside (SNP)] vasodilators. We evaluated whether a dynamic approach using spectral analysis of the blood flow signal, resulting from the cutaneous red cell flux and recorded by the technique of laser Doppler flowmetry (LDF), can detect higher endothelial responsiveness in trained versus less trained individuals. There was a 1.6 times higher ACh-induced cutaneous perfusion in athletes than in controls (P