Carbonfiberboy 

My sample size is pretty small, but from what I've seen, PTs are pretty good. My aunt's PT is a whip-smart educated woman heading for medical school. She's totally rebuilt my aunt as a human being. In my gym, the PTs are fit, educated, certificated, and from what I've seen, know what they're doing. It really, really helps to have a coach watch you when you work out, at least until you have your form down and have a program. I have a "coach", a world class powerlifter, who's been a lot of help to me. He formally coaches several very strong young women, no funny business. He just like to coach women, I think because they do what he tells them to do. Men can be idiots.

You know you have a good doctor if you do your research and cite some new studies to him/her, and the doc has read the studies and can place them into the panoply of medical knowledge for you. My doc's like that and he's in his 60s. Good doctors read medical journals in bed.

I have friends my age tell me about how they hurt their back or whatever, by picking up something heavy and twisting to set it down again. Yep, don't go to the gym, do you? In a way, only cycling makes it worse for us geezers, because some things get strong, but others keep getting weaker. Makes it easier to damage ourselves off the bike.

Further, on the subject of bone strength, walking is helpful for maintaining bone density or at least minimizing bone loss: https://www.ncbi.nlm.nih.gov/pubmed/8304358
To increase bone density takes more. Box jumping is really good, up and down. Impact multiplies your weight by acceleration multiples, IOW the g's you pull when you hit. Easy to get 5 g's or more = 750 lbs. for me.

Here's something really simple you can do every day: put on your socks and shoes while standing on one leg. If you don't do this now, it's not that easy but you'll definitely improve over time. Also brush your teeth while standing on one leg. This improves lower leg strength and your priopreception, key to preventing falls.