Resting Rate

• In most cases, your heart will beat somewhere between 60 and 100 times a minute while you are at rest. This basic rate is called the resting rate and is usually lower in people who are more physically fit. A high resting rate is the sign of a body that needs more activity and even low-impact exercises like walking can help improve the heart's natural performance.
  
  

Maximum Rate

• As you exert yourself, your heart rate increases to pump oxygen rich blood to muscles which now need it to perform at their peak. At low levels of activity, the heart has no problem maintaining this supply, but with continued or more vigorous exertion it will have to work harder and harder to keep the blood flowing and the oxygen moving. Maximum heart rate varies from person to person, but a basic formula is 220 beats per minute minus your age. Therefore, a healthy 30-year old man would expect his maximum heart rate to fall somewhere near 190 beats per minute.
  
  

Exercise Levels

• Exercise intensity can be measured by the resulting heart rate, falling into five broad categories. Below 60 percent of your maximum heart rate is considered a warm-up level, but this intensity is also good for those who are out of shape or otherwise unfit. At 70 percent of maximum, your body shifts into a fat-burning mode, which makes this plateau excellent for burning calories. 80 percent sees a shift to aerobic respiration, with the maximum usage of oxygen throughout the body and good cardiovascular utilization. At 90 percent, the body begins to run out of oxygen, and muscles begin to "burn" as they feel the deprivation. Pushing beyond this level truly brings the body to its limits and can't be maintained for long even by world-class athletes.
  
  

Cardiovascular Exercise

• If you live a relatively sedentary lifestyle, one good way to improve your overall fitness level is by developing your cardiovascular system. Pushing yourself past three-quarters of your maximum heart rate fully engages your heart and lungs, and maintaining this level of exercise can help increase endurance and overall health. It's important to warm up to this level of exertion, however, especially when starting a new exercise routine.
  
  

Lifelong Fitness

• By engaging in regular exercise that brings up your heart rate, you can not only burn fat and carbohydrates, lose weight, and gain more energy, but you can keep the most vital parts of your body in good shape. Regular cardio workouts will strengthen and maintain your heart, reducing your resting rate as well as improving your body's circulatory and respiratory efficiency.