For muscle strengthening, use light weights and more repetitions.
Resistance bands might be a safer choice compared to free weights.
Don't lift weights while flat on your back.. It can inhibit blood circulation.
For aerobics, the recommendations are either walking for about 11 hours a week, or swimming or riding a stationary bike for about five hours a week.
And listen to your body. If you feel any kind of strain o fatigue modify the moves and reduce the frequency of your workouts.
