BACKGROUND: The eccentric (ECC) training, in spite of its potential interest (slightest request of the cardiorespiratory system) compared with the concentric (CON) training, is not applied during the rehabilitation of the chronic heart failure (CHF). The main reasons are the difficulty personalizing the ECC exercises by avoiding the muscle complications and the lack of information concerning the specific effects on the maximal capacities in CHF patients. AIM: To compare - following a prior study on the feasibility and on the functional impacts - the effects on maximal capacities and tolerance in CHF of ECC training tailored by a low rate of perceived exertion (RPE) and those of conventionally tailored CON training. DESIGN: Prospective randomized comparative study. SETTING: A Rehabilitation Department in a University Hospital. POPULATION: CHF outpatients with reduced ejection fraction randomized to either ECC (N.=21) or CON training (N.=21). METHODS: ECC and CON training were respectively tailored by a low RPE (RPE between 9 and 11 on the Borg scale) and a heart rate (HR) corresponding to the first ventilatory threshold. Cardiopulmonary exercise test, maximal muscle strength tests (quadriceps, triceps surae) and 6-minute walk test were performed before and after training. Tolerance to training was assessed by RPE, muscle soreness, increase of HR, blood pressure and plasma NT-proBNP. RESULTS: Improvement in peak work rate was similar for both groups (+20%, P<0.01), but VO2 peak and VO2 at the first ventilatory threshold were only increased in the CON group (+13.5%, P<0.01). Maximal strength of the triceps surae was increased in the ECC group only (+23%, P<0.01). Improvement in the walk test distance was similar in both groups, but the corresponding VO2 was only increased after CON training. Tolerance to training was good in both groups, except higher increment of training HR in the CON group (P<0.05). CONCLUSIONS AND CLINICAL REHABILITATION IMPACT: ECC training tailored by a low RPE is well tolerated in CHF patients and induces an improvement in maximal capacities similar to that with conventional CON training despite lower demands on the cardiorespiratory system, showing a better energetic efficiency, potentially interesting for these patients with reduced energetic reserve.