This study investigated the physiological effects of sail pumping (PB)--a manoeuvre often adopted to provide additional propulsion to the board--in Olympic Class Windsurfing, following relaxation of the "no-pumping" rules by the International Federation. Fifteen Olympic-level windsurfers (10 men) from nine different countries volunteered for the study, which was performed during two international Olympic regattas. The measurements were carried out during actual sailing when both PB and not-pumping (NPB) using a portable metabolimeter. Windsurfing, when PB, elicited a dramatic increase in cardiorespiratory responses compared to NPB. Mean (SD) values for oxygen uptake and heart rate during NPB for the men and women were: 19.2 (4.4) and 15.7 (3.3) ml x kg(-1) x min(-1), and 110 (10) and 122 (12) beats x min(-1), respectively, whereas the values in PB were: 48.4 (5.7) and 40.2 (4.2) ml x kg(-1) x min(-1), and 165 (12) and 172 (13) beats x min(-1), respectively. All the PB parameters, with the exception of heart rate (HR), were significantly higher in the men than in the women but no differences were observed between the sexes in NPB with the exception of HR, which was higher in the women. Our results suggest sail pumping is as physically demanding as most aerobic sporting activities. In the context of the need to deal with a highly demanding athletic branch of sailing as part of an Olympic regatta, recommendations are made on how best to make physical and dietary preparations.