In neuroscience, rheobase is the minimal current amplitude of indefinite duration (practically, a few hundred milliseconds) that results in the depolarization threshold of the cell membranes being reached (i.e. an action potential or the contraction of a muscle).
In the case of a nerve or single muscle cell, rheobase is half the current that needs to be applied for the duration of chronaxie to result in an action potential or muscle twitch.[1] This can be understood better by looking at a strength duration relationship (Fig. 1).[2]