Here's all a 50 plus person needs to do for exercise to maintain health
Here's exactly what I do to stay trim and fit in my 50's, and I don't overdo it which many people do. You must know your limitations at this age and not push or you will injure yourself...eventually. This has worked for me
I require one hour of physical training per day with maybe a day off in the mix. I swim a straight hour in the pool every other. I walk 2.5 miles on the odd day schedule with swimming session. Every other day I lift weights for 20 minutes. I can eat pretty much what I want within reason, don't go nutty crazy or anything but I eat Burger King or Taco Bell during the week when I want, I eat healthy dinners, breakfast is always cereal with banana and blueberries...always.
Do this and you'll slowly but surely get your body used to daily exercise, maintain and grow muscle that displays well, and cardio will increase. I don't get injured, I can handle this routine, I don't talk myself out of it, this works.