October 22, 2017
Target Heart Rate: Wrong Number?

Target Heart Rate: Wrong Number?

by Berkeley Wellness  

Target heart rate for aerobic exercise is the number of heart beats per minute that you should aim for to get cardiovascular benefits. The first step is to compute your “maximum heart rate” (MHR)—and the conventional way to do this has been to subtract your age from 220 (and then multiply the result by various percentages, as discussed below).

This MHR formula, which provides a rough estimate, is used by the American Heart Association, CDC, and many other organizations because of its simplicity. It is also programmed into many exercise heart rate monitors and gym machines. But it has been much criticized in recent years, and at least a dozen alternative age-related formulas have been proposed, with no clear winner. For most people these new formulas produce only slightly different results from the old one.

False precision?

Many factors besides age affect heart rate and its response to exercise, which can vary greatly from person to person. The only way to come up with a meaningful MHR is with an exercise stress test, in which you exercise at increasing intensity while your heart is monitored with an electrocardiogram. But that’s expensive and usually unnecessary.

One complaint about the old formula is that it was developed using data predominantly from young and middle-aged men, and that it produces targets that are too low for older women, in particular. Exercise stress tests show that MHR declines with age, but more gradually in women. Thus some newer formulas differentiate between the sexes. For instance, new ones from researchers at the Mayo Clinic say that women over 40 should multiply their age by 67 percent (that is, by 0.67) and subtract the result from 200 to get MHR, while men should multiply their age by 93 percent (0.93) and subtract the result from 216. Some other researchers have concluded that the gender differences for MHR are not significant.

Many fitness experts, including those at the nonprofit American Council on Exercise, go with an alternate MHR formula developed by researchers from the University of Colorado more than a decade ago—208 minus 70 percent of age—which aims to be more accurate for older people. For a 50-year-old, it produces an MHR that’s only 3 beats per minute higher than the old formula does (173 vs. 170). But for a 70-year-old, the new result would be 9 beats higher (159 vs. 150).

Finding an accurate MHR formula may be important for exercise physiologists and perhaps professional trainers, but for regular exercisers this is a matter of false precision. For one thing, MHR is only the first step in figuring out your target heart rate (“training zone”) for exercise, which is usually a pretty broad range and also open to debate. Typically, target heart rate is 60 to 80 percent of MHR if you have been exercising aerobically at an intermediate level. If you are mostly sedentary, 50 to 60 percent of MHR is an appropriate starting range. If you’re well trained, you can go to 90 percent or higher for an intense workout. You can use this quick online calculator to find your optimal range.

Stop counting

Target heart rate can be a useful tool when you begin exercising, but soon you won’t need to focus on it. Once you learn how it feels to work out in your training zone, you should be able to estimate the intensity of your activity just by focusing on how you feel—for instance, how hard you are breathing, how much strain you feel, and how much you are sweating. This is called the “rate of perceived exertion.” You can also use the simple “talk test.” If you can speak only short sentences, the intensity is moderate. If you have trouble speaking, you’re exercising too strenuously; if you can easily have a conversation, your workout is too easy. Studies have shown that both approaches are fairly accurate.