[en] Evolutions of the local pressure gradient and the amplitude of the helical mode are studied near the critical pressure gradient against the linear resistive interchange instability in the high aspect ratio toroidal helical plasmas. Three characteristic dynamic evolutions are identified; monotonous saturation, relaxation oscillation and periodic limit cycle solution. As the heating power is increased, the dynamic evolution changes from the monotonous saturation, to the relaxation oscillation and finally to the limit cycle. The time average of the pressure gradient is limited by the critical gradient against the linear stability. Dependences of the amplitude and period of the sawtooth oscillation on the heating power are also analyzed. (author)