Purpose The aim of the present study was to understand the role of central (cardiovascular O2 delivery) and peripheral factors (muscle level) in limiting the maximal aerobic performance in obese (OB) subjects. Methods Fifteen OB (mean age± SD 25 ± 7 years; BMI 43± 7 kg/m2 ) and 13 lean sedentary subjects (CTRL, age 27±7 years; BMI 22±3 kg/m2 ) participated in this study. Oxygen uptake (VO2), hearth rate (HR) and cardiac output (CO) were measured during cycle ergometer (CE) and knee extension (KE) incremental tests. Maximal voluntary contractions (MVCs) of knee extensor muscles were performed before and immediately after the two tests. Results VO2peak, HR peak and CO peak were signifcantly higher in CE than KE (+126%, +33% and +46%, respectively, p0.05, for CE and KE, respectively). Conclusions The lower muscle fatigue observed in OB after CE compared to KE test suggests that central factors could be the most important limiting factor during cycling in OB.