Exercise Junkies: How Hard Should You Push Your Heart?
WebMD News Archive
If the new formula is adopted by the American Heart Association, it will change the advice doctors give their patients, he says. The predicted maximum heart rate reflects what people should achieve when they do their physical activity.
"Heart rate is a reasonably good indicator of the target rate at which any level of athlete should be exercising, but it tends to be variable based on your physical shape," says Manoukian. "If you're in bad shape, your heart rate jumps up quickly; if you're in good shape, it tends to be harder to achieve."
As a rule of thumb, he says, for someone first starting an exercise program, "we would advise working to 50% of your maximum heart rate, then gradually up to 75 or 85%. With healthy adults, we advise to keep challenging themselves to exhaustion."
Even more importantly, the new formula would affect exercise stress tests that cardiologists give to people with heart problems.
"If you came into my office with chest pain, I would put you on a treadmill and monitor your ECG -- I would like to get your heart rate up to 85% of your predicted maximum heart rate," says Manoukian. "Only at that level can a cardiologist provide any significant information about heart function. If I'm inaccurately calculating what maximal is for you, I may not be getting the maximal test."
Also, those with heart disease -- especially if they're over 50 and 60 -- may also be able to exercise at higher heart rates than previously thought, Manoukian tells WebMD.
For most healthy adults without heart problems, the American Heart Association's FIT (frequency, intensity, and time of exercise) recommendations are: frequency of five times week, intensity that is "somewhat hard," and 30-60 minutes of exercise at a time, he says.
"I often tell people to exercise to the point where it feels challenging, that you could have a conversation but exercise might make you somewhat breathless," says Manoukian. "If you're not breathless, you're not exerting enough. You should perceive the exercise to be somewhat difficult."
The American Heart Association has no plans to change its current policy endorsing the 220 - age formula, says Gerald Fletcher, MD, a cardiologist at the Mayo Clinic in Jacksonville, Fla., and a member of the AHA's Council on Clinical Cardiology. "There are many ways to look at maximal heart rate, and the current formula still gives a reasonable prediction," he tells WebMD. "This might in the future help us look at things differently, but right now we're going to stay with it."