How much do you know about your heart? Not the heart that loves and breaks, but the amazing organ in your chest. How does exercise affect your heart? And can fitness be measured by heart rate?
The Heart – An Amazing Machine
The average human heart weighs only about 10 ounces, and is around the size of an adult’s fist. It has four chambers which pump five to six quarts of blood through your body every minute.
The heart works in tandem with the lungs to keep oxygen flowing to cells and removing carbon dioxide waste products. The heart pumps oxygen-laden blood coming from the lungs to all parts of the body, via arteries. Once the oxygen in the blood is used by the cells, the deoxygenated blood is pumped back through veins to the heart and then the lungs. The lungs oxygenate the blood from the air you inhale, and release carbon dioxide through your exhale. The newly oxygenated blood is pumped back into the heart and then out to the body, coming full circle.
A heart “beat” is really a muscle contraction, followed by a release of that contraction. Compare this to squeezing a half-empty bottle of dish soap. You turn it upside down and squeeze to expel the soap (the contraction); when you stop squeezing (the release), there’s a rush of air that’s sucked back into the bottle (often making a silly sound.) That’s basically what your heart is doing to pump blood.
Exercise and Your Heart
When you exercise, your muscles require more oxygen. This means your heart must beat faster to pump more oxygenated blood, at a quicker rate, to meet this demand. Because the heart is itself a special type of muscle, it is strengthened by the “exercise” it gets when it’s required to beat faster. This is why cardiovascular exercise (“cardio”) benefits your heart. The stronger your heart, the more easily it can pump blood. Added benefits of a strong heart are lower blood pressure, improved overall blood circulation, lower blood cholesterol levels, and reduced resting heart rate.
Heart Rate as a Measure of Intensity
Heart rate (aka pulse rate) has been used for decades as a gauge of exercise intensity and overall wellness. Heart rate-based training is used by exercisers of all types to ensure they are working hard enough, but not too hard, based on their objective for a particular exercise session. Heart rate, however, is not a perfect measure because of an effect known as cardiac drift. In very simple terms, cardiac drift is the gradual increase in heart rate over time while exercise intensity remains constant. The result is that your heart rate may indicate you are working at a slightly higher intensity than you actually are.
Heart Rate and Fitness Level
Two additional measures of heart rate that gauge overall fitness are Resting Heart Rate and Recovery Heart Rate.
Resting Heart Rate (or pulse) is the number of heartbeats per minute when you are completely at rest. Typically this is when you awaken in the morning and before you get out of bed. Measure this for three days in a row and take the average to determine your normal Resting Rate. Going forward, compare your Resting Rate on a particular day to your “normal.” A Resting Rate that’s lower or higher than normal can indicate you are overtrained, and/or you’re coming down with an illness. If so, it may be time for extra rest and recovery days.
Resting Heart Rate can also be a measure of overall heart health. The American Heart Association notes that a “normal” Resting Heart Rate for adults over 18 years is anywhere from 60 to 100 beats per minute. In general terms, the lower your Resting Rate, the stronger your heart muscle. Elite athletes have been known to have Resting Rates in the 40 bpm range.
Recovery Rate Heart (HRR) is a measure of how much your heart rate drops during the first minute after peak exercise. This is a simple way to measure your cardiovascular fitness and track improvement. Take your heart rate for one minute immediately after stopping an intense bout of exercise. Wait one minute, then take it again for another minute. If your one minute heart rate has dropped by 15 to 25 beats, you’re in the average or better range for healthy adults. The more your heart rate drops in that minute, the faster your heart is recovering – and therefore the healthier your heart. If your heart rate drops by only 12 or fewer beats in the first minute after exercise, you should visit your doctor before continuing to exercise at higher intensities.