Don't laugh, there is a program, which is free from some Medicare plans, called Silver Sneakers. Geared towards seniors, of course. Some exercises are very mild, others can provide good conditioning. The one near us, which my wife uses, is too easy, but the gym is still free, so I use their weights and machines. But another, a bit further away, really provides a workout. And at one of them, we found out about a rec center that offers a free exercise program for seniors. It utilizes weights, stretch bands, and various exercises such as jumping jacks, stretches, cardio, etc., etc., which offers even a fit person a good workout, and you can work at the exercises as hard or as easy as you want, so good for all levels. There are some Silver Sneakers workouts on YouTube also. I scoffed at them at first, but if you consistently work at them, have found them helpful in maintaining fitness.