Your target heart rate is the range at which sustained physical activity - running, cycling, swimming laps, or any other aerobic exercise - is considered safe and effective.
Learning how to prevent knee injuries and treating them if they occur can help you stay active at work and play.
Ideally, exercise should become something you do without question, like brushing your teeth, says the President's Council on Physical Fitness and Sports. As you work your way toward that goal, be patient. It will take a little time to regain your fitness, especially if you've been sedentary for years.