Ask The Doctors: April 2019
Q: When I exercise, my pulse quickly rises from about 70 beats per minutes (bpm) to 140 bpm and, occasionally, to 160 bpm, but quickly drops back to 70 bpm when I stop. I experience no adverse symptoms and can talk while exercising. I am 86, and this exceeds the recommended maximum heart rate for me. Should I be concerned?
A: It is normal for heart rate (HR) to increase during activity in order to provide nutrients and oxygen to exercising muscles. The formula for obtaining your maximum predicted HR-220 minus your age-tends to underestimate maximal HR by as much as 10 to 20 beats, particularly at older ages. However, an exercise HR of 160 seems high, particularly since a lack of symptoms and ability to talk normally with exercise does not suggest a very high exertion level.
A higher-than-expected HR doesn't always indicate a problem, but several issues need to be considered. Make sure your HRmeasurement is accurate. Many wrist monitors and hand-grip HR monitors on exercise equipment are imprecise.
If the measurement is accurate, you must exclude circumstances that may contribute to a higher HR with activity, including exercising in a hot environment or deconditioned state, dehydration, fever, caffeine use and certain medications and medical conditions. You need to determine whether your rhythm is normal but fast or abnormal. For example, atrial fibrillation rates often increase rapidly with exercise and a less common condition causes rapid increases in HR with activity, but is typically associated with a high resting HR and shortness of breath, lightheadedness and, sometimes, chest pain. Your doctor may want to obtain a physical exam and simple blood tests to exclude secondary causes, and maybe an ECG and ambulatory HR monitor and/or stress test to accurately determine your heart rate responses.
Q: I want to start exercising by walking or using a treadmill. What is the best way to make sure that I am doing enough exercise to achieve cardiovascular benefit?
A: The American Heart Association recommends a minimum of 150 minutes of moderate or 75 minutes of vigorous aerobic activity weekly to get maximal benefit. A simple way to determine whether your exercise intensity is meeting these goals is to assess your level of perceived exertion. During moderate activity, you should notice an increase in breathing rate, but not become out of breath. You should experience mild-to-moderate sweating and be able to carry on a conversation but not be able to sing. If you cannot say more than a few words without stopping for a breath, you are engaging in vigorous activity.
Intensity can also be gauged by measuring your HR while exercising. One simple way is to subtract your age from 220 (see first Q&A). A revised formula that may be more accurate is to multiply your age by 0.67 and subtract it from 207. Moderate intensity is 50to 70 percent of maximal: vigorous is 70to 85 percent. There is little reason to exceed 85percent.
If you are age 55 with a maximal projected HR of 170 bpm and resting HR of 70 bpm, your HR range for moderate intensity activity is 120 to 140 bpm.
Always check with your doctor before initiating an exercise program. If you are just beginning to exercise, start at the lower range of 50 percent and work up gradually. Always stop and seek medical attention if unusual symptoms develop. Certain medications and medical conditions can change the maximal HR achievable and be a reason for lower intensity goals. In these cases, an exercise stress test would give you a more precise measurement of your maximal projected HRand help determine the safest level of exercise for you to perform.