re: Weight training in your 40s advice

No idea. I’m 53 and have not stopped weight training since I was 15.

In my 40s and not nearly as fast and agile as my younger days and pretty sure I will never dunk, or try to dunk a basketball again, but I'm still gaining strength and generally keeping a flat belly.

My quick 5 steps:
1) find a good long-term progression lifting program and stick to it with minor adjustments, unless you have uber specific goals don't change up too much week to week
2) try to have a solid, clean diet as much as possible while getting enough calories and protein. For me, if not lifting and staying active I can drop weight too easily which affects my workouts.
3) no more heavy bulk/intense cut cycles, I try to keep generally the same diet and weight year round. Drawback is it can be much harder to gain strength, but my gains are generally true gains that I can maintain.
4) integrate mobility into your workouts, especially accessory work
5) listen to your body...at least once a month I have a workout where I switch out accessory work due to something not feeling right and sometimes even stop after finishing my main lift. Better to back off and live another day then push too hard and get injured (if you are young please ignore that!). If it happens multiple times then it probably means I'm going too heavy and need to back off and see if I have a form issue or other problem.

This