Muscle nuclei were isolated using a modified version of the 10x Genomics Chromium Nuclei Isolation Kit for Single Cell Multiome ATAC + Gene Expression. In brief, approximately 50 mg of flash frozen gastrocnemius muscle were pulverized in Covaris tissueTUBE TT2 with one pulse of the CP02 cryoPREP Automated Dry pulverizer at the highest impact setting. Pulverized samples were transferred to pre-chilled sample dissociation tubes provided in the 10x Genomics Nuclei Isolation Kit, and nuclei were isolated as directed in the manufacturer's instructions. Nuclei suspensions were diluted to 1,000 nuclei/l using fluorescent nucleic acid staining (AOPI), and nuclei quality was confirmed under 40x magnification. The single nuclei suspension was loaded onto Chromium X (10x Genomics) for targeting of 6,000 nuclei, according to the manufacturer's instructions. Libraries were constructed using Chromium Next GEM Single Cell 3' Kit v3.1 (10x Genomics). Quantity and quality of cDNA and indexed libraries were determined with Qubit 1X dsDNA HS Assay Kit (Thermo Fisher Scientific) and High Sensitivity DNA ScreenTape Analysis (Agilent).