Your heart rate increases when you exercise, because you are working harder. How much your heart rate increases depends on the intensity of your exercise and how fit you are. Exercise experts differ on how high your heart rate should be during exercise, but they agree that it needs to be substantially higher than your resting heart rate to improve your cardiovascular fitness. Exercise experts also agree that improved cardiovascular fitness improves your resting and recovery heart rates.
As soon as you begin exercising, your skeletal muscles contract and "squeeze the veins near them, forcing blood toward the heart," explains The Merck Manual of Medical Information. Your skeletal muscles become a de-facto "second heart" as they contract and relax, pumping extra blood to your heart. The extra blood causes your heart rate to increase. This process means that putting more strain on any of your skeletal muscles, such as your arm muscles and leg muscles, increases the blood flow to your heart and your heart rate.
Resting Heart Rate
Your resting heart rate shows your baseline cardiovascular fitness. The best time to measure your resting heart rate is right after you wake up, before you sit up. Measure your heart rate, which is also known as your pulse, by placing your forefinger or middle finger, or both, on the carotid artery of your neck. Count the number of heartbeats per minute to get your heart rate. Average resting heart rate is 60 to 75 heartbeats per minute. A resting heart rate above the average can be improved by exercising your heart, and a resting heart rate below the average means you are very fit.
Exercise expert Dr. Kenneth Cooper says that an exercise heart rate that is 65 to 80 percent of your maximum heart rate, MHR, will improve your cardiovascular fitness. However, Dianne Hales, the author of "An Invitation to Health," recommends that you increase it to 60 to 85 percent of your maximum heart rate. And Fenton recommends exercise heart rates of 55 to 65 percent of MHR for 3-mile-per-hour walks, 65 to 75 percent of MHR for 4-mile-per-hour walks and 75 to 90 percent of MHR for 4.5-mile-per-hour walks. Your MHR , if you are male, is 220 minus your age. If you are female, multiply your age by 88 percent and subtract that number from 206 to obtain your MHR.
Increasing your heart rate through exercise makes your heart more accustomed to performing well when a lot of blood is pumped to your heart. Improved performance increases the amount of blood pumped by your heart during one heartbeat. These changes decrease your resting heart rate and improve how quickly your heart recovers after you exercise, returning to a resting heart rate.