Fitness Goals Support Group
This community is dedicated to group support around achieving fitness goals, whatever they may be, through personal training, athletic activites, or other strenuous activity. Whether you are trying to get fit to treat a health problem, boost your mood, relieve stress, or tone your body, this group is a great place to meet other like-minded people who have similar goals.

I'd suggest, using very VERY lightweights and do more reps. use 2 lbs, 50 times instead of 20 lbs 5 times. This will be easier on the joints, and help with flexibility too, since you'll be moving thru the range of motion more times.
I also use 1, 3, & 5 lb rubber bands, their color coded and offer some great resistance. DON'T OVER DO IT!!!!! ;-)
https://www.sharecare.com/health/fitness-exercise/article/exercise-20-minutes-a-day-to-keep-muscles-young?eid=1010716381&memberid=61238435&_sid=null&
Myself I'm 52 and doing 30 minutes of cardio per day on a elliptical and slinging around 60lb kettlebells and free weights for bodybuilding. I started about two years ago after a 10 year break. LOL