DMD and Duchenne muscular dystrophy: The cluster analysis in the plot of TA weight and muscle strength from p16+/+, p16+/−, and p16−/− WT rats, and p16+/+, p16+/−, and p16−/− DMD rats revealed there were 4 groups, within which almost all rats with WT background were accumulated in 1 group, and rats with DMD background were divided into 3 groups (Fig. 3c).