The performance of high current discharges can be improved by applying central I CRF heating before or shortly after the onset of sawtooth activity in the plasma current rise phase. Long sawtooth-free periods have been obtained which result in a transiently-enhanced discharge performance. High Te(0) =9-10.5 keV with peaked profiles Te(0)/ < Te > = 3-4 were obtained giving values of ne(O)Te(O) up to 6 1020 (keV m-3). Improvements in Ti(0) and neutron production are observed. A best value of nD(0)Ti(O)τE = l.65 1020 (m-3 keVs) was achieved. Local transport simulation shows that the electron and ion thermal diffusivities do not differ substantially in the two cases of current-rise(CR) and flat-top(FT) heating, the performance of the central plasma region being enhanced, in case of current-rise, entirely by the elimination of the sawtooth instability. The maximum D-D reaction rate is enhanced by a factor 2 compared to flat-top value An appreciable part of the reaction rate is attributed to 2nd harmonic deuterium (2ωCD) heating. In all current-dse discharges radiation amounts to 25-50% of total power and Zeff remains roughly constant.