THE PHYSICIAN AND SPORTSMEDICINE - VOL 29 - NO. 7 - JULY 2021
New Formula Estimates Maximal Heart Rate
What Are the Clinical Considerations?
The age-predicted maximal heart rate formula that has been used for about three decades to gauge fitness levels and set exercise goals has been recalculated by Colorado researchers who hope to make the formula a more accurate reflection of true maximal heart rate. Their findings were published earlier this year in the Journal of the American College of Cardiology (1).
Meta-analysis Meets the Lab
Hirofumi Tanaka, PhD, lead author of the study and an assistant professor in the Department of Kinesiology and Applied Physiology at the University of Colorado in Boulder, says that his group had noticed a shortcoming of the original formula (220 - age) (2,3). "In our lab, we study aging and cardiovascular function, and we noticed that with most subjects, the maximal heart rate is higher than their age-predicted maximal heart rate," he says. "We thought there might be something wrong with the old equation." In past years, other researchers and clinicians had also noticed the discrepancy between the two values, but the Colorado researchers are the first to propose a new equation based on broad age and fitness-level ranges of healthy subjects. From a meta-analyis of 351 studies that involved 18,712 subjects, they proposed a new formula: 208 - 0.7 X age. When cross-validating their findings with a controlled laboratory study that measured maximal heart rate in 514 subjects, they arrived at the same formula. They confirmed that maximal heart rate is influenced by age and is independent of gender and fitness level.
Tanaka and colleagues note that the clinical implications of their findings are that the original equation overestimates maximal heart rate in young adults, intersects with the new equation at age 40, then increasingly underestimates maximal heart rate in older adults. They note that the need for a more accurate equation is most crucial for older people, who are most often the group in greatest need of an exercise prescription for the treatment of cardiovascular and chronic diseases. Direct maximal heart rate measurement requires strenuous effort, which can be risky in this population.
One caution that Tanaka notes is that the new equation contains a 10-bpm standard deviation. "If the opportunity allows, get a maximal heart rate," he says. In the conclusion of the study, the authors also suggest that clinicians use subjective exercise effects that rate as "somewhat hard" or "hard" on the Borg perceived exertion scale.
Victor Froelicher, MD, director of the ECG/exercise laboratory at Palo Alto VA Health Care Systems and professor of medicine at Stanford University, says the Colorado group's study is excellent and is consistent with data from his lab. He notes that cardiologists and researchers have had concerns over the accuracy of the old equation for some time. "Even the exercise testing guidelines state this and recommend that age-predicted heart rates not be used," says Froelicher, who is an editorial board member of The Physician and Sportsmedicine. The new equation is likely to be eventually accepted into clinical practice. Froelicher notes that other tools for gauging maximal heart rate, such as expired gas analysis, are finding their way into clinical practice.
Paul Thompson, MD, director of preventive cardiology at Hartford Hospital in Hartford, Connecticut, and professor of medicine at the University of Connecticut School of Medicine in Farmington, Connecticut, says he believes the take-home message from the study for physicians is to avoid depending on predictive equations. Thompson, who is an editorial board member of The Physician and Sportsmedicine, advocates using subjective measurements to tailor exercise prescriptions. "People, in my opinion, should pay less attention to heart rates and more attention to how they feel," Thompson says.
A Spotlight on Mascot Injuries
A survey documenting the high rate of mascot injuries was presented by Johns Hopkins researchers in June at the annual meeting of the American College of Sports Medicine in Baltimore. The group surveyed all professional mascots in baseball, football, and basketball. From 48 returned surveys, researchers identified 179 injuries during mascot participation. (The rate appears to be lower than that for other professional sports.) The knee was the most common injury site, followed by hand/wrist/finger, and ankle. Ankle sprain was the most common acute injury reported, and 44% of mascots noted a history of chronic low-back pain. Twenty-two injuries required surgical repair.
Heat injury was reported among 28 mascots; 14 required intravenous fluids, 6 were diagnosed with heat stroke, and 1 was hospitalized. In fact, the researchers concluded that heat illness may be the most important health problem in this population.
Several mascot injuries have made headlines. In November 1999, Ball Hog, a mascot with the former Edmonton Drillers of the National Professional Soccer League, was playing in a sports celebrity soccer exhibition game and was knocked down by an Edmonton Oilers player. The impact caused a metal screen inside the costume to cut the mascot's forehead. In 1997, a University of Cincinnati student who wore the Bearcat mascot costume at basketball games was hospitalized when he suffered a severe respiratory attack that was thought to be related to the heat inside the costume.
Date Set for 2021 Sports Medicine Exam
Registration for first-time applicants begins on July 2, 2021, and must be postmarked by September 30, 2021. Registration for reregistrants begins September 1, 2021, and must be postmarked by November 30, 2021. The final month of each registration requires payment of a late fee.
First-time applicants using fellowship training to qualify may complete their applications online at https://www.abp.org. Eligibility requirements can also be found on the ABP Web site.
Registrants who hold primary certification in family practice, emergency medicine, or internal medicine must contact their respective boards about registration dates and application.