The muscle fiber CSA was measured using laminin staining as previously described (4 (link),6 (link)). Briefly, all mouse tibialis anterior muscles were fixed, flash-frozen, and cryosectioned into 10-µm thick sections. The middle third of each muscle was sliced. The sections were incubated in the presence of anti-laminin antibody (Abcam) at 4 °C for 12 h, and then incubated with fluorescent secondary antibody (Alexa Fluor, Invitrogen, USA) at room temperature for 1 h. Five slices were selected from each muscle sample. The slides were observed and imaged under fluorescence microscopy (ZEISS, Oberkochen, Germany) and the CSA was determined using ImageJ software [National Institutes of Health (NIH), Bethesda, MD, USA] through blinded analysis of five randomly captured images under each detection condition.