How many days a week should seniors exercise?

As suggested by the Physical Activity Guidelines for Americans, you should exercise at least 150 minutes a week at a moderate intensity, such as brisk walking or dancing quickly. Ideally, one should be active at least three days a week, but anything is better than nothing. It would be a good idea to do muscle-strengthening exercises at least twice a week. For example, lifting weights or doing sit-ups.
In the Physical Activity Guidelines, it is also recommended that you combine different components of exercises into your weekly physical activity schedule. For example, you should try balance exercises, aerobic exercises, and muscle-strengthening exercises. Try to do vigorous-intensity aerobic activities (like running) for at least 75 minutes a week.