The average resting heart rate is 60 to 75 heartbeats per minute, and athletes' heart rates are often less than 50 beats per minute, according to "The Complete Guide to Walking." Your heart rate should increase when you are active. It can go as high as 220 heartbeats per minute minus your age when you exercise very intensely. A lot of exercise that increases your heart rate can lower your resting heart rate, according to The Merck Manual of Medical Information.
Explanation
Your heart rate, how many times your heart beats in a minute, is determined by "how hard the skeletal muscles contract," The Merck Manual of Medical Information reports. Your skeletal muscles don't move when you are at rest, but they are squeezed together when you move. Muscle contraction squeezes nearby veins and forces blood toward your heart. Higher blood flows cause your heart to beat faster. More intense activity causes greater skeletal muscle contraction and a faster heartbeat.
Significance
A low resting heart rate "indicates" your fitness level and cardiac strength are high, the "Guide to Walking" reports. Strengthening your heart requires exercise that increases your heart rate "at least 20 beats above the resting heart rate," according to The Merck Manual of Medical Information. If your resting heart rate is 60 beats per minute, you improve your heart muscle and fitness the more your activity heart rate exceeds 80 beats per minute. A stronger heart pumps more blood per beat and, thus, beats at a lower rate at rest.
Intensity
Exercise experts use the term "intensity" to measure your activity level. Intensity is expressed as percentage of your maximum heart rate, or MHR. Your MHR is 220 heartbeats per minute minus your age or 180 heartbeats per minute if you are 40 years old. Your intensity is 50 percent of MHR if you are 40 years old and your heart rate is 90 beats per minute while you are exercising.
Activity Levels
A chart in "Guide to Walking" shows how activity influences heart rate. Walking at a "moderate" 3.5 mph pace for 30 minutes causes your heart rate to be about 60 percent of your MHR or 108 heartbeats per minute—180 times .6—if you're 40 years old. Walking 4 mph for 45 to 60 minutes increases your heart rate to about 70 percent of your MHR or 126 beats per minute—180 times .7. "Fast walks," walking faster than 4.5 mph, increases your heart rate to about 80 percent of your MHR or 144 beats per minute—180 times .8.
Expert Advice
Dramatic changes in your heart rate in a very short period of time can harm your heart by interfering with the "adequate transfer of blood volume from the exercising limbs," according to "Swim, Bike, Run." Authors Glenn Town and Todd Kearney, former competitive triathletes that are now medical professionals, recommend that you do warm-up and cooldown exercises for 10 to 20 minutes each when your intensity will be at least 80 percent of MHR.
References
- The Merck Manual of Medical Information; 1999
- "The Complete Guide to Walking;" Mark Fenton; 2001
- "Swim, Bike, Run"; Glenn Town and Todd Kearney; 1994
- "Dr. Dean Ornish's Program For Reversing Heart Disease"; Dr. Dean Ornish; 1996
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