I'm 55 and just started back at the gym during lunchtime. I have a long history of joint damage, suffer with a frozen shoulder that's filled with arthritis. Also about 35 lbs over weight. I have read that older folks should stick to machines as they limit range of motion and reduce risk of injury. I prefer staying with dumbbells. Standing arm raise front and side, standing curls, some bench work, all using weight that I can comfortably manage 4 sets of 12 reps. Now just a couple weeks in I can already tell my shoulders don't cry out as loudly. Mixing in core (sit-up bench) and long walks with interspersed jogging (with my Five Finger toe shoes
) for cardio.