Answer: for transfection of the muscle cell line, electroporation is applied to it. muscle cells are suspended in a conductive solution. An electrical pulse at an optimized voltage and only lasting a few microseconds to a millisecond is discharged through the cell suspension. This disturbs the phospholipid bilayer of the membrane and results in the formation of temporary pores. The electric potential across the cell membrane simultaneously rises to allow charged molecules like DNA to be driven across the membrane through the pores in a manner similar to electrophoresis

I'll second Kodagoda Thudugalage Nimalsha Hansani 's answer. In my experience primary muscle cells are very poorly transfectable using systems like Lipofectamine and display a fair amount of cytotoxicity following extended transfections (e.g. >4 hr). I've also noticed that these cells take longer to express exogenous genes (even from mRNA transfection) than other cell types like HeLa or HUVECs.

electroporation could be a good choice.