A question I’ve received a lot after spending this month talking about heart rate is:
“Why is my heart rate so high when I exercise?”
Those who ask this are seeing their heart rate climb to 80 or 90% of their max on a relatively easy bout of exercise. If an easy workout should only get the heart rate to 60-70% of their max, what gives?
First, it’s important to understand why training at a near-max heart rate for long durations can be detrimental or even dangerous. One study* of recreational hockey players found that those who continuously exceeded their target and maximum heart rates while playing had poor rates of recovery after exercise. They also increased their risk for arrhythmias (an irregular heartbeat) and chest pain.
Another issue is that when your heart rate is too high, you’re training the lactic threshold system, which only helps you with shorter bursts of exercise. This isn’t inherently a bad thing, but you end up undertraining your body’s ability to burn fat for fuel. Conversely, if you're always training at a high heart rate, your body won’t be able to recover enough to properly train the lactic threshold system. Let’s find out what’s going on.
First, make sure your tracking device is accurate. You can do this by comparing it against a manual test (measuring your pulse and counting yourself) or against a chest strap monitor. Next, try keeping a log of your workouts alongside your heart rate measurements, noting the time of day and how much caffeine you’ve had. Since caffeine elevates the heart rate, it could be contributing to false high measurements.
If your heart rate monitor is accurate and you’re not consuming anything that’s raising your heart rate, try paying attention to other cues your body might be giving you. If you end up feeling dizzy, light-headed, or close to hyperventilating, your heart rate has been too high for too long and you need to get it down to be able to continue exercising safely. Do so by easing up just a little bit until you feel better or take a few moments to regain your composure and your breath.
Lastly, if you’re over 35, I’d suggest you visit your physician and discuss your heart rate. Your physician may recommend a max stress test, which provides very helpful diagnostic information. A maximal stress test for a runner would be a treadmill test that begins at an easy level and then increases in intensity every three minutes by upping the speed and the incline of the treadmill. Your heart rate and blood pressure are measured at each stage. Once the intensity level goes up, but your heart rate does not, you know you are at your max. You can use this data to better understand how your body responds to exercise.