Aerobic exercise is a way for people of all ages to improve their cardiovascular health, lose or maintain body weight, and even elevate their mood. It's important, however, to have an idea of the proper intensity level you should shoot for and to have an objective metric to use in determining this intensity level. One such metric is heart rate, which correlates strongly with both perceived and actual work output.
Heart Rate and Age
The maximum heart rate, or MHR, you can reach is a function of age and is commonly estimated by subtracting your age from 220. A 2001 study by Hirofumi Tanaka and colleagues at the University of Colorado found that the formula 208 minus 7/10 of age is more accurate in that it reflects the tendency of the MHR to slow by less than a beat per year in healthy adults. Alternatively, according to exercise physiologist Pete Pfitzinger, MHR can be assessed directly by running for two to three minutes up a moderate incline three times with jogs to the bottom in between; your heart rate at the end of the third repetition will be very close to MHR.
Heart Rate Range
No matter what your age is or your fitness goals are, the range in which your heart rate should be maintained as a function of MHR to achieve significant cardiopulmonary gains is the same. You should aim to keep your heart rate between about 60 percent and about 80 percent of MHR. Going into higher ranges for brief periods of time -- perhaps 10 to 20 minutes per week -- is acceptable, and for athletes preparing for certain sporting events this is even desirable. However, while this might make you faster, it won't make you healthier.
Variation in Heart Rate
According to longtime UK Athletics distance-running coach Brian Mackenzie, a reduction in heart rate at a given intensity level most often results from an improvement in fitness level, but in the short term, other factors can throw off the heart rate-intensity relationship. For example, dehydration can increase it by up to 7.5 percent, heat and humidity can increase it by 10 beats per minute, exercising at high altitude can increase it by 10 to 20 percent, and normal biological variation can produce a day-to-day fluctuation of two to four beats per minute.
Perceived Exertion Versus Heart Rate
Another indirect way to assess your heart rate is the Borg perceived exertion scale, which runs from 6, or "no exertion," to 20, or "maximal exertion." Because healthy younger people typically have a heart rate of about 60 at rest and a MHR of about 200, the Borg scale has been correlated in numerous studies with heart rate, with actual heart rate being 10 times the perceived exertion. However, because of the age-related decline in MHR, you must adjust this correlation factor accordingly. For example, if your resting heart rate is 50 and your MHR is 150, then a 13 on the Borg scale -- halfway between minimum and maximum -- will correlate with an actual heart rate of about 100.
References
- "Journal of the American College of Cardiology"; Age-Predicted Maximal Heart Rate Revisited; Hirofumi Tanaki, Kevin D. Monahan, Douglas R. Seals; 2001
- DistanceCoach.com: How To Obtain Optimal Results Using a Heart-Rate Monitor
- Brian Mac Sports Coach: Heart Rate Training Zones
- Centers for Disease Control and Prevention: Physical Activity for Everyone
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