Mice with DJ‐1‐specific knockout in skeletal muscle show decreased muscle mass and impaired exercise performance. (A) Western blot analysis of DJ‐1 in GAS of muscle‐specific DJ‐1 knockout (MDKO) and Flox mice. (B) DJ‐1 expression level in GAS by qPCR. (C) Body weight of male MDKO and Flox mice fed on chow diet (n = 8–9). (D) Body composition and muscle weight of male MDKO and Flox mice at the age of 18 weeks (n = 7–8). Fat mass, lean mass, GAS weight. (E) Tibialis anterior (TA) muscle force analysis of male mice at the age of 18 weeks (n = 5). Specific titanic force of TA muscles (A), relaxation time (B). (F) Exercise performance tests. Grip strength of mice at the age of 13 weeks (n = 8) (A). Maximum load capacity of mice in a resistance test at the age of 14 weeks (n = 8) (B). Maximum hanging time with four or fore limbs of mice at the age of 15 weeks (n = 8) (C, D). Rotarod performance test of mice at the age of 16 weeks (n = 8) (E). Total time, maximum speed, and total distance of mice in exhaustion test at the age of 17 weeks (n = 8) (F). Data represented the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, a two‐tailed Student's t‐test was used for statistical analysis.