Move it or lose it!
Our bodies must have regular static stresses pushing through our bones and muscles to keep working.
At least walking and standing as much of the day as possible will be a good start, but improvement in muscle power and bone health needs high intensity training. Try high intensity training for 20 minutes, 3 times per week, doing activities like: skipping, jumping pushups or squats. Do as many repetitions of the exercise as you can in 30 seconds with a short rest in between sets. Only this type of training can build new muscles and stimulate brain cells to protect themselves.