I vividly remember reading an article in Guitarist magazine with Jack Bruce and he said that he didn't pick up his bass unless he was writing a song. At the time I couldn't imagine this as the first thing I did when i got home from school was plug in and play until tea time. Fast forward 38 years and I don't pick up my bass unless I have something to learn. Last year I took a year out after 30 years of constant playing and maybe picked up my bass a handful of times, only to make sure that I could still play.
Regarding losing muscle mass as we get older - this is called sarcopenia and is though to begin when we're in our 30s. They can't work out if it's due to not moving as much in adult life as we did when we were kids or if it's just an age thing but it's a huge issue.
This is why I train at the gym. I don't want to be Arnie and walk around like I'm carrying a roll of carpet under each arm, I'm doing it as a preventative measure to try to avoid being frail with arms like knitting needles and not able to walk the length of myself when I get old.
This is another reason why protein is so important for everyone, not just people who go to the gym, as it can help slow this down as well. Just remember to eat plenty of fibre to keep it moving otherwise you can end up getting bunged up 😫🥴
I'm grateful that approaching 50 I am not on any medication as I know a lot of people, some younger than me, who are already rattling with what they have to take. I do currently take Turmeric & black pepper tablets in the morning, Creatine at 11am, fish oil and magnesium bisglycinate at tea time and zinc monomethionine before bed.
Once great exercise I like to finish with at the gym is the farmer's walk. For me it's picking up 2 16kg kettle bells and walking as far as I can with them. Sounds crazy but if you think about it, we all do the farmer's walk carrying gear in and out of gigs so it keeps me in practice between gigs to keep the strength.