Aerobic activity improves your cardiovascular health and helps protect against heart disease . It also improves your physical energy and produces endorphins that improve your mood.
What you do and how often and hard you exercise are determined by your goals, present fitness level and health, interest, and convenience. It is important to choose an activity you enjoy and that fits your lifestyle and tailor it to your fitness level. This will help you make exercise a habit. It's also a good idea to choose more than one type of exercise to give your body a more complete workout and to avoid boredom.
There are two great ways to increase aerobic benefits:
Instead of doing only moderate-level activities, consider replacing some with vigorous aerobic activities that will make your heart beat even faster. Adding vigorous activities provides benefits in less activity time. In general, 15 minutes of vigorous activity provides the same benefits as 30 minutes of moderate activity.
Have you been walking for 30 minutes five days a week? On two days, try jogging instead of walking for 15 minutes each time. Keep on walking for 30 minutes on the other three days.
Already doing two hours and 30 minutes a week of aerobic physical activity? Good for you! Do you want to gain even more health benefits from physical activity? Slowly add more time to your weekly routine.
Strive to double your weekly activity time. Work to be active five or more hours each week for even more health benefits. A recent study in the Journal of the American Medical Association found that an hour of exercise each day can help adults maintain a healthy weight and avoid long-term weight gain.
You can do all moderate activities, all vigorous activities, or some of each. You should always start with moderate activities and then add vigorous activities little by little.
Would you like to have stronger muscles? If you have been doing strengthening activities two days a week, try adding an extra day.
One way to set your goals and monitor your level of physical activity is to know your target heart rate . Make your cardiovascular workouts hard enough to break a sweat and get your heart pumping faster. Learn how hard you should work out. 
Walking is one excellent cardio-respiratory exercise that almost everyone can do. Walking 10,000 steps a day can improve health and fitness. (It takes a little more than 2,000 steps to walk one mile.) Many people discover when they begin wearing a pedometer that they only average between 900 and 3,000 steps a day. Learn how to start your own walking program .
There are many choices for cardiovascular exercise. Learn some of the pros and cons  of each to help you make choices.