The Relationship Between Heart Rate & Exercise

Heart rate reflects exercise intensity.
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Exercise directly affects the activity, function and health of your heart. In the short term, your heart rate increases in proportion to your level of exertion as you exercise. Regular aerobic exercise strengthens your heart over time. As your cardiovascular fitness improves, the level of heart rate increase necessary during strenuous physical activity diminishes.

Oxygen-Demand Response

Your muscles use oxygen to generate energy. The oxygen taken in with each breath dissolves in your blood. Your heart pumps blood to your muscles and body tissues, delivering the oxygen needed to keep them functioning. Your muscles' demand for oxygen increases sharply when you exercise. The higher demand for oxygen stimulates a rise in heart rate, which increases the amount of oxygen-rich blood delivered to your muscles. During vigorous exercise, blood flow to your muscles can be 25 to 50 times greater than when you are at rest.

Conditioning Effect

When you exercise, your heart gets a workout along with your muscles. Like other muscles in your body, your heart gets stronger in response to regular exercise. A strong, exercised heart pumps more blood with each beat compared to an untrained heart. Because a well-conditioned heart pumps more blood, the heart rate does not rise as dramatically in response to exercise. Similarly, the resting heart rate decreases as heart fitness improves because a well-conditioned heart delivers the same amount of blood with fewer beats.

Target Heart Rate

Improving your cardiovascular fitness requires challenging your heart to work harder. Monitoring your heart rate during exercise is the best way to determine whether your heart is getting an adequate workout. Your age influences the target heart rate for optimal cardiovascular conditioning. To calculate your target heart rate, subtract your age from 220 to get your maximum heart rate. For example, the maximum heart rate for a 40-year-old is 180 beats per minute. The target heart rate during moderate-intensity exercise is 50 to 70 percent of the maximum heart rate; this would be 90 to 126 beats per minute for someone age 40. During vigorous exercise, the target heart rate is 70 to 85 percent of the maximum heart rate, which would be 126 to 153 beats per minute for a 40-year-old.


The U.S. Department of Health and Human Services recommends that all adults perform a minimum of 150 minutes of moderate-intensity exercise or 75 minutes of vigorous-intensity exercise weekly for cardiovascular and overall fitness. Keeping in mind that your target heart rate determines whether a workout is moderately or vigorously intense, certain forms of exercise typically fall into one category or the other. Options for moderately intense exercise include brisk walking, dancing, hiking, water aerobics, yoga, table tennis and softball. Examples of vigorously intense exercise include running, race walking, rock climbing, jumping rope, stair climbing, singles tennis, soccer, basketball and football.

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