Oxygen consumption of working muscles depends on oxygen delivery and oxidative capacity of muscle. The aim of the study was to compare dynamics of cardiac output (CO), blood filling of working muscle and muscle oxygen consumption evaluated by common hemoglobin (cHb) and deoxygenated hemoglobin (HHb) accordingly during incremental test. 7 young men and 8 athletes performed bicycle incremental ramp test till exhaustion. CO was determined up to maximal aerobic power (MAP) by open-circuit method using gas mass-spectrometer. HHb and cHb concentrations were continuously evaluated in m. vastus lateralis (VL) by near- infrared spectroscopy. HHb in athletes increased linearly till exhaustion. Untrained subjects demonstrated slowing down of HHb increase at submaximal aerobic power. The observed differences could be connected with low oxidative capacity of muscle or with restricted oxygen delivery to the muscle. Indeed untrained subjects demonstrated slowing down of cHb in VL at 50–80 % of MAP, while the athletes showed an increase of cHb up to 90–100 % of MAP. Half of the subjects demonstrated slowing down of CO increase at 90–100 % of MAP. The dynamics of CO was not related to dynamics of cHb in VL. That means that oxygen delivery to working muscle at maximal aerobic power may be limited both by CO and/or by redistribution of blood from working muscles to other regions, for example, to respiratory muscles. Thus comparison of CO dynamics with that for cHb and HHb in working muscle allows to reveal the factors limiting individual aerobic performance. The work was supported by RFBR grant #60-04-49699a.