A–E, motor end‐plate labelling with α‐bungarotoxin (green) and anti‐neurofilament plus anti‐synaptophysin antibodies (NF+Synaptophysin, red), representing a typical pretzel‐shaped (A, left) and a fragmented NMJ (A, right), in the soleus of sedentary control mice (B), sedentary type 3 SMA‐like mice (C) and running‐trained (D) or swimming‐trained type 3 SMA‐like mice (E) at 12 months of age (scale bars: 5 μm for A and 10 μm for B–E). F and G, quantification of the neuromuscular junction fragmentation (F) and area (G) in the soleus, plantaris and tibialis muscles from sedentary control mice compared to sedentary, running‐trained (Run) or swimming‐trained (Swim) type 3 SMA‐like mice at 12 months of age (n = 4 in each group). Data are represented as means ± SD (*P < 0.05).