Long-term improvements in muscle strength observed by functional and physiological testing of OPN^−/−mdx mice. (A) Hanging wire test (n = ≥9 per genotype and age). (B) Grip strength test (n = ≥9 per genotype and age). (C) Wire mesh test (n = ≥10 per genotype and age). (D) Body weight (n = ≥9 per genotype and age). (E) Specific force (n indicated on bars of the graph). (F) Serum creatine kinase (n = ≥6 per genotype and age). (G) Minute ventilation (n = ≥10 per genotype and age). (H) Peak inspiratory flow (n = ≥10 per genotype and age). (I) Peak expiratory flow (n = ≥10 per genotype and age). Vertical lines represent standard error. *, P < 0.05; ^#, P ≤ 0.02, determined by analysis of variance model.