Heart rate estimation shot down by experts

Monday, February 17, 2014

“Subtract your age from 220” is a familiar bit of exercise class math. It’s the first step for figuring out maximal heart rate - the top number used in heart rate target zone training.

People who try to keep their pulse racing within certain ranges during exercise first estimate their maximal rate and then take percentages of it. (Read an explanation of the method from the Centers for Disease Control and Prevention at tinyurl.com/220minus.)

Gym rats might reasonably assume that the maximal heart rate formula is based on a large, reliable body of data, since it is so widely employed by coaches, athletes, physicians and all those target-heart-rate posters hanging in gyms.

But in fact the formula has been largely discredited.

Originally derived by compiling data from studies conducted in the 1960s and ’70s of cardiac health among adult men, the formula was a drastic simplification of those findings, said Ulrik Wisloff, the director of the K.G. Jebsen Center of Exercise in Medicine at the Norwegian University of Science and Technology in Trondheim.

From the first, the formula was not very accurate for almost anyone, he said, but its simplicity was appealing.

The more researchers study the issue, the more unreliable the formula proves. A large-scale 2010 study of women, for instance, concluded that more accurate numbers for that sex would be 206 minus 88 percent of a woman’s age, while various studies of older adults, college students, adolescents and children each have concluded that the standard formula was off-base for them, too.

“The traditional formula can underestimate heart rate max by up to 40 beats per minute in [the elderly],” Wisloff said, “and starts becoming inaccurate already at the age of 30 or 40 years.”

Wisloff recently oversaw a study of heart rate calculation.

According to his group’s examinations of 3,320 men and women between the ages of 19 and 89 who participated in a wide-ranging health study in Norway, a better formulation for both sexes would be 211 minus 64 percent of age.

Should the brain revolt at the thought of the math required to determine maximum heart rate using those numbers, Wisloff’s lab has posted a simple calculator online at ntnu.edu/cerg/hrmax.

Bear in mind that knowing your maximum heart rate is “not needed to have effective training sessions,” Wisloff said. “But many people find it motivating,” especially when the formula is correct.

Celia Storey added some information to this report.

ActiveStyle, Pages 23 on 02/17/2014