Can you push a heart patient too hard? A recent article in the Wall Street Journal revealed that a major American medical center is encouraging some recovering heart attack patients to do what is called “high-intensity interval training” (HIIT) – short bursts of heavy exercise that force the heart to beat at 85 to 95 percent of its maximum rate. Ordinarily, heart patients have been urged to take a moderate and steadier route to fitness, maintaining the heartbeat at about 70 percent of the max. More intense exercise, it is feared, might trigger an arrhythmia or cardiac event. But now, some experts are saying that bursts of high-intensity exercise may be beneficial to some patients with coronary artery disease, heart failure, or those recovering from heart attacks or bypass surgery.
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“HIIT is an extension of a well-established athletic training principle into cardiac rehab,” says Gordon Blackburn, PhD, program director of Cardiac Rehabilitation at the Miller Family Heart & Vascular Institute. “Studies across the board have shown that a broad spectrum of heart patients experience greater improvement in functional capacity using HIIT compared to the traditional steady state exercise that shoots for 60-75 percent of maximum heart rate.” He notes that although the studies have not been especially large, “There has been no increased level of complications or untoward events and compliance has been better than steady state exercise.”
Stanley Hazen, MD, PhD, head of the Section of Preventive Cardiology and Rehabilitation, says “Increased functional capacity is a good thing.” But he points out that there should be a clear distinction between HIIT and more sustained intensive exercise, like marathon running. “There are many papers showing more cardiac troponin positivity [a marker of damage to the heart muscle] after strenuous exercise bouts.” Indeed, in a 40-minute moderate exercise session, only 8-10 minutes would be in the high-intensity mode – 30 to 120 seconds per bout.
The value of cardiac rehabilitation is well-documented in the 60-70 percent capacity range. But Dr. Blackburn cautions that “While exercise capacity may be improved, there is no mortality or morbidity benefit data based on the HIIT algorithm. So while we prescribe HIIT training for a few select patients, we still recommend that most patients follow a steady, moderate (60-70 percent of maximum heart rate) exercise program for cardiac rehabilitation
BONUS: Mnemonic Moment
The Wall Street Journal article on HIIT also mentions an informal trick for remembering your maximum heart rate: subtract your age from 220 and the number that remains is a rough estimate of your upper limit.
“This applies to a healthy population but may be grossly inaccurate for patients with heart conditions or those taking medications such a beta blockers,” cautions Dr. Blackburn Another good rule of thumb is simply to “listen to your body”, and slow down if you feel uncomfortably overexerted.