As soon as you begin to exercise, your body increases its demand for oxygen. Your breathing rate increases so you can get more oxygen into your lungs, and your heart rate increases to pump freshly oxygenated blood around your body. To get the most out of your workouts, especially cardiovascular activities such as running, cycling, swimming or rowing, it is important that you keep your heart rate within a specified range. Numerous methods can calculate your heart rate range and measure your heart rate during exercise.
Heart Rate Training Zone
When performing cardio, your heart rate should be between 60 and 90 percent of your maximum. This is commonly referred to as your training zone. Going below 60 percent means you may not be exercising hard enough to elicit an improvement in fitness; going over 90 percent means you may be exercising too hard.
The Karvonen formula is a simple calculation to learn your age-adjusted maximum heart rate and your training zone. The calculation is:
220 - age in years x 60 percent 220 - age in years x 90 percent
These figures represent the low end and high end of your heart rate training zone, and you should endeavor to keep your heart rate between the two.
Heart Rate Reserve
Critics of the Karvonen formula say that while the calculation is suitable for some exercisers, it doesn't take into account that fitter people are often comfortable exercising at higher heart rates than the less fit. Heart rate reserve takes into account your resting heart rate. A low resting heart rate is an indicator of superior cardiovascular fitness.
To obtain your resting heart rate, measure your pulse for a minute when you feel completely relaxed and well rested. Repeat the test a few times to ensure you have an accurate figure. To calculate your training zone with heart rate reserve, use the following formula:
220 - age - resting heart rate x 60 percent + resting heart rate 220 - age - resting heart rate x 90 percent + resting heart rate
These figures represent the low end and high end of your heart rate training zone and you should endeavor to keep your heart rate between the two.
Maximal Heart Rate Test
While Karvonen theory and heart rate reserve are useful and simple to use, they do not always provide an accurate heart rate training zone; they treat everyone as being the same. For a more individualized heart rate training zone, experienced and already fit exercisers can perform a maximum heart rate test, also known as a stress test.
You can perform a maximum heart rate test using a variety of exercise modalities including rowing machines, treadmills and exercise bikes, as well as running or cycling outdoors.
After a suitable warm-up, begin exercising normally and gradually increase your pace. Continue to get faster until you feel you are working as hard as you possibly can. Keep on exercising a little longer until you have to slow down or stop. On completion, immediately take your heart rate, ideally using a heart rate monitor for accuracy. Use the same basic Karvonen calculation as before, but substitute your new maximum heart rate for the age-adjusted one.
Caution: Maximum heart rate tests are for advanced, fit and healthy exercisers only and should not be attempted by anyone else unless under the direct supervision of a doctor.
Measuring Your Heart Rate
Different methods can measure your exercising heart rate and ensure you are in your training zone. Heart rate monitors use a chest strap and receiver watch to measure and display your heart rate. Some monitors have programmable alarms so that the watch will beep if you stray from your training zone.
Alternatively, you can take your own pulse at your wrist or neck. Count your heart rate for 15 seconds and then multiply by four for a rough estimate of your heart rate.
Some cardiovascular exercise machines have built-in heart rate monitors that measure your pulse when you grip specially designed handles, although these tend not to be as accurate as chest strap heart rate monitors.
- ACSM's Resources for the Personal Trainer; American College of Sports Medicine
- Essentials of Strength Training and Conditioning; Thomas Baechle and Roger Earle
- Exercise Physiology: Theory and Application to Fitness and Performance; Scott K. Powers and Edward T. Howley
Patrick Dale is an experienced writer who has written for a plethora of international publications. A lecturer and trainer of trainers, he is a contributor to "Ultra-FIT" magazine and has been involved in fitness for more than 22 years. He authored the books "Military Fitness", "Live Long, Live Strong" and "No Gym? No Problem!" and served in the Royal Marines for five years.