Growth of muscle upon functional overloading. (A) Plantaris muscles of control (ctrl) and RAmKO mice were functionally overloaded (FO) by ablation of the soleus and gastrocnemius muscles. Muscle weight of plantaris was measured after 7 or 28 days of FO and is expressed as the percentage of the weight of the contralateral, non-overloaded muscle (7 days FO: N ≥5 mice; 28 days FO: N ≥7 mice). (B, C) Fiber size distribution of the contralateral (dashed line) and FO (closed line) plantaris muscle of control (B) and RAmKO (C) mice after 28 days of FO (N = 7). (D) H&E staining of overloaded and contralateral plantaris muscles after FO for 28 days in control and RAmKO mice. (E) Muscle weight after 28 days of FO in control and TSCmKO mice (N = 5). (F) Fiber size distribution of non-overloaded, contralateral (dashed line) and over-loaded plantaris muscles (solid line) after 28 days of FO in TSCmKO mice (N = 5). (G) H&E staining of overloaded and contralateral plantaris muscles after 28 days of FO from TSCmKO mice. (H, I) NADH-TR staining of plantaris muscles after 28 days FO in mice with the indicated genotype. Scale bars (D, G, H, I) = 50 μm. Individual data points and bars of quantitative data represent mean ± SEM. P-values are ***P <0.001; **P <0.01; *P <0.05; Student’s t-test.