Possibly related: there's some indication that sarcopenia (age-related reduction of myofiber size) is related to a decline in the availability of muscle stem cells - and (in a different study) creatine can help slow (or reverse?) the decline.

Further afield, given that we're talking about muscle cell groups and associated nerve cells, there's been some interesting work showing that nerve cell decline is related to reduced oxidative capability, and that, in turn is related to downregulated cytochrome oxidase, which impairs the electron transfer chain. There's also work with both methylene blue, in low dose (MB acts as an electron donor) and transcranial IR lasers (photons act as electron donors) to both reactivate the ECT and (in a way I don't understand - and maybe it's just not understood) upregulate cytochrome oxidase and to reverse long term damage. This is all in vitro, in mice, and the human studies are all around the CNS, so I have no idea how applicable it might be to muscle related nerves. I'd dig up references, but Medium has made inserting links into responses a major PITA (thanks, Medium!) so I might get around to inserting those, but I'll take their crippling of the response editor to mean they're discouraging that, so probably not. Glad to send them out of band, though...