Have you ever finished a workout, looked at your heart rate data and thought with alarm, “Whoa, that seems high!” I have. I was concerned when I saw 200 beats per minute on the screen after going for a run that did not seem particularly strenuous.
In medicine, there is a saying that in an emergency, the first pulse that you check is your own. If a wrist wearable is giving you a measurement that is alarming, double check it against a manual pulse check. You may not be able to manually check your pulse at the peak of your exertion during a workout, but you can check right afterwards, or even at rest. This will at least give a couple data points with which to assess the accuracy of your wearable monitor. I find that mine is less accurate at higher heart rates.
The second question to ask yourself is whether you’re having any symptoms. A high heart rate without symptoms is much less concerning than a high heart rate that accompanies chest pain or shortness of breath. If you have symptoms, those should be investigated in consultation with a physician before participating in the exercise.
If you’re wondering where you fall in the range of ‘normal,’ the traditional formula for calculating maximum heart rate is 220 - age. However this was based on a small cohort of mostly men under age 55 published in 1971. Endurance guru Phil Maffetone, in his Big Book of Endurance Training and Racing, notes that “In reality, most athletes who obtain their maximum heart rate by pushing themselves to exhaustion will find it is probably not 220 minus their age. About a third will find their maximum is above this heart rate, a third will be below, and only a third may be close to what they've calculated. These inaccuracies are often significant.”
What happens when you push to exhaustion? I had a sports performance lab do just that for me on a treadmill. When I had my VO2 max tested at age 41, my maximum heart rate was 183 beats per minute, a far sight from the 200 bpm off my wrist watch, yet not far from the 179 predicted by the 220 - age formula.
Research studies have attempted to elucidate more accurate predictors of maximum heart rate in adults at risk for cardiovascular death. Naturally, data specific to older populations and populations that include more women are valued here. Predicting a maximum heart rate is useful, because it helps clinicians know whether an exercise stress test was sufficiently strenuous.
One study of 31,090 patients found that a better predictor of maximum heart rate was 197 - 0.8 x age for women and 204 - 0.9 x age for men. This would predict a lower max heart rate for me (204 - 0.9 x 41 = 167.1). In my case, the old formula (from the study of men under 55) is more concordant than this newer, gender-specific formula.
If you look at Figure 1 from that study, however, you’ll note that there are plenty of data points on either side of the regression line. My 183 is well within an area of high data point density. So if your observed heart rate maximum doesn’t match the predicted, you’re in good company. Remember that research studies report what’s true for groups of people, not individuals.
The question of how often you should be exercising to max effort is another question that deserves attention. The answer is that one should spend a relatively small amount of time at that level of exertion. This balance of effort will optimize training adaptation (good stress) and avoid the bad stress that leads to overtraining and injury. A study of cortisol levels in saliva in healthy adults doing various amounts of high intensity interval training found a correlation between time spent at greater than 90% maximum heart rate and variables associated with overtraining. The authors concluded that the ideal duration of time spent training at greater than 90% of heart rate maximum was 4-9% of total training. HIIT training is fun and efficient, but should be a small proportion of your overall program.
So next time you see a heart rate pushing 200, take note of how much time you’re spending in that zone, and make sure the bulk of your endurance training at lower effort is enough to support the time spent at the top of the intensity pyramid.