Abstract: A system for determining a bending moment on an oar during a rowing stroke in the water has an oar handle, an oar shaft that extends from the oar handle, an oar blade that is disposed on the oar shaft on the side opposite the oar handle, at least one strain gauge, from the signal of which the bending moment can be determined, wherein the oar shaft is of a multi-part form and wherein a measuring sleeve, which joins the two adjacent parts of the oar shaft to each other and which comprises the at least one strain gauge, is disposed between two adjacent parts of the oar shaft. With a rotation measurement of the oar by an additional MEMS, the power against time of the rower can be determined by multiplication of the determined angular rate and the bending moment.