['Previous studies of biomechanical efficiency (external work/energy input--Watt/O(2) consumed) in heart failure (HF) using cardiopulmonary exercise testing (CPET) and magnetic resonance spectroscopy (MRS) have had discordant results with increased efficiency by CPET and decreased efficiency by MRS.', 'Compare biomechanical efficiency of HF subjects and normal controls during steady state (SS=35 W for 6 min) and ramp cycle ergometer exercise. The hypothesis was that HF subjects would have impaired biomechanical efficiency that correlated with HF symptoms.', 'Biomechanical efficiency used the actual Vo(2) during exercise and recovery. Gross (Vo(2) above zero), Net (Vo(2) above the resting Vo(2)) and Work (Vo(2) above the unloaded pedaling Vo(2)) efficiencies were calculated.', 'HF subjects had an 18% higher Vo(2) during SS exercise (P=0.029). Biomechanical efficiency was reduced during SS exercise (gross -15%, P=0.019, net -15%, P=0.062, and work -35%, P=0.002). Gross Efficiency during SS exercise had the strongest correlation with HF symptoms (r=0.55). During ramp exercise gross (-26%), net (-10%) and work (-8%) biomechanical efficiency were all reduced (all P<0.05). The slope of the Vo(2)/Watt relationship during ramp exercise had the best correlation with HF symptoms (r=0.46).'] Is biomechanical efficiency decreased in heart failure during low-level steady state and maximal ramp exercise?