Previous investigations into peak cardiac power output (CPOpeak) have been limited to clinical populations and healthy, but nonathletic adults, and normative data on trained individuals would allow a greater understanding of this parameter. Following ethics approval, eight healthy, well-trained male cyclists were recruited. Peak oxygen consumption (VO2peak) was assessed using an incremental ergometer test, and after a 40-min recovery period, peak cardiac output (QTpeak) was measured during a constant load test that elicited VO2peak (±5%) using the Defares CO2 rebreathing technique. CPOpeak was calculated (CPO peak=MAP×QT×K, where mean arterial pressure (MAP) is given in mm Hg, QT in l/min, and K is the conversion factor 2.22×10-3, which expresses the output in watts (W)). Mean (SD) values during the constant load test were: VO2peak, 4.94±0.41 l/min; QTpeak, 36.5±3.7; mean arterial pressure, 123±8 mm Hg and CPOpeak, 9.9±1.0 W. These results demonstrate CPOpeak in a well-trained population to be approximately twice that observed in healthy, but nonathletic adults. The current data provide useful information regarding the upper limits and possible “trainability” of cardiac pumping capacity for sedentary and clinically compromised individuals.