Trains of APs in WT and DMD ^mdx muscle fibers. Representative records of the changes in membrane voltage elicited by short suprathreshold depolarizing current pulses delivered during 3 s at the indicated frequency, in a WT and in a DMD^mdx muscle fiber. Superimposed red lines at the end of the 20-, 50-, and 80-Hz records correspond to the result of a single exponential fit (see text for details, section: APs).