In 2014, it was estimated that about 20% of American adults wore an activity tracker like a “Fitbit.” And it wouldn’t surprise me if that number has jumped substantially in the last three years. But is it really helping you? Well, it might surprise you that this popular device could actually be increasing your risk for a heart attack or another cardiovascular event.
Activity Tracker Heart-Rate Monitor May Be Misleading
A recent study found that the heart-rate monitor on wrist-worn activity trackers can be inaccurate, perhaps overestimating or underestimating heart rate by about 40 beats per minute (BPM). This is a massive swing that could cause someone to unknowingly go well above their target heart rate, posing a particular problem for people with existing heart conditions.
The study found that when compared to comprehensive electrocardiogram (EKG) monitors to track heart rate, wrist-worn activity trackers could have some pretty big swings and misses. Thankfully, however, the discrepancies were only noticed during periods of exercise. In fact, for the most part, the trackers were on or near the mark.
Tracking BPM During Exercise
So whether this is a big issue or not comes down to what you’re using it for.
If you’re using your activity tracker to keep a general record of your heart rate and other health statistics, you don’t have much to worry about. But if you’re using it for medical purposes or to carefully track BPM during exercise, it could be inaccurate and lead to problems.
For example, if you’re a 65-year-old with a heart condition and your doctor has instructed you to exercise at no more than 60% of your maximum heart rate, you’ll be aiming to keep it around 93 BPM (your max heart rate is roughly 220 BPM minus your age). If you’re exercising and your activity tracker underestimates your heart rate by 40 BPM, you could be putting yourself at risk for a heart attack from working out too intensely.
Don’t Just Rely on Your Activity Tracker
So what should you do? I definitely would not recommend throwing away your fitness tracker. It can be a decent way to keep track of your heart-rate averages and seems to be relatively accurate most of the time. Instead, when you are exercising, pay more attention to physical feelings rather than just glancing at your Fitbit or other fitness tracker.
To achieve 60% to 70% of your max heart rate, you can, for example, take a brisk walk or go for a light jog, depending on your fitness level. You should be sweating lightly, but still be able to maintain a conversation without gasping for air. When you get up to 80% or higher, you will likely be unable to say more than a few words, while you’ll feel your heart beating rapidly.
If you have an existing heart condition, it’s highly recommended that you speak to your doctor before beginning any exercise regimen—and remember, your Fitbit can be helpful, but it should not be used for medical purposes.
“Don’t Bank on Heart-Rate Accuracy From Your Activity Tracker,” MedlinePlus web site, April 10, 2017; https://medlineplus.gov/news/fullstory_164546.html, last accessed April 12, 2017.