SR Ca ²⁺ release parameters in WT and DMD ^mdx muscle fibers. (A–D) Individual and corresponding mean (±SD) values for maximum rate of SR Ca²⁺ release (Max), voltage of mid-activation (V_0.5), slope factor (k), and total amount of released Ca²⁺ ([Ca_Tot]), respectively, in WT and DMD^mdx fibers (data are from 29 fibers from seven WT animals and 27 fibers from seven DMD^mdx animals). Each bar and superimposed data points correspond to data from a same animal. Values in A–C were obtained from fitting a Boltzmann function to the peak SR Ca²⁺ release versus voltage relationships. For Max, V_0.5, k, and [Ca_Tot], P = 0.011, 0.21, 0.42, and 0.49, respectively (nested t test). For V_0.5, k, and [Ca_Tot], the 95% CIs for the difference between mean values are: −11.07 to 2.69, −2.29 to 1.03, and −910.6 to 461.5, respectively. 95% CI, 95% confidence interval.