Technology has turned fitness into a fashion trend. Lots of people use wearable fitness trackers to monitor their step count and exercise, even to track heart rate data. But how accurate are fitness trackers at measuring steps, calorie burn, sleep quality and heart rate?
These wearable devices or smartphone apps have become an essential tool for anyone looking to improve their health and fitness. Look around your office or gym, and it’s a safe bet to assume most people will be wearing a fitness tracker of some sort. In fact, the Pew Research Center reports 1 in 5 Americans wear either a smartwatch, pedometer or other fitness tracker daily.
What do fitness trackers do?
Fitness trackers, or activity trackers, are devices or apps that monitor your physical activity throughout the day. They use a combination of sensors – including accelerometers and gyroscopes – to detect movement and track metrics like daily steps, distance traveled and calories burned. Some newer models of fitness trackers even include features like heart rate monitoring, sleep tracking and GPS.
How accurate are fitness trackers?
Fitness trackers can help you achieve wellness goals through data and awareness. They have become much more affordable and common, so many people rely on them to monitor their fitness progress, set goals and stay motivated.
How accurate are fitness trackers, and how much do they actually benefit you?
“I think they are useful, but they’re not always going to tell the truth – that a patient is having an arrythmia or other electrical disturbance of the heart,” Jeff Senfield, MD, a cardiologist at Bon Secours Upstate Cardiology Greenville. “However, they may tell you if something else is going on. So, I think it’s a good thing for a lot of people. For everyday fitness, it’s good to know what your heart rate is, especially if you want to target a certain heart rate zone during exercise.”
With so many different devices on the market, it’s essential to understand how accurately these devices measure the metrics most important to you.
Tracking steps
One of the most popular features of fitness trackers is step counting. Tracking daily steps is the simplest way to monitor physical activity and stay on track with fitness goals. But do they accurately measure your steps?
In general, fitness trackers are pretty accurate when measuring steps. They rely on accelerometers to detect motion, registering each step based on the device’s movement. However, the accuracy of step counting can vary depending on the type of activity, the placement of the device and the model of the fitness tracker.
For instance, walking on a flat surface at a consistent pace may yield very accurate step counts. However, running, cycling or hiking up and down hills can be more difficult for fitness trackers to measure. If you wear the tracker in a less-than-ideal position (like your pocket or loose on your wrist), the device may miss some steps or overestimate the number of steps.
Most trackers are fairly accurate within a small margin of error – usually within 5 to 10 percent of your true step count. However, some models perform better than others, especially those incorporating advanced sensors or machine learning algorithms to refine step counting.
If you’re simply looking for a general estimate of how many steps you’ve taken throughout the day, fitness trackers will likely provide a good approximation. But if you’re aiming for precise, clinical-level data, it’s important to understand the limitations of these devices.
Calorie burn estimation
Calorie burn is another critical metric that many fitness tracker users care about. Fitness trackers calculate calories burned based on data like steps taken, heart rate, distance traveled and activity level. However, accurately estimating calorie expenditure can be more challenging than measuring steps.
Several factors impact the accuracy of calorie burn estimates, including:
- Age
- Weight
- Gender
- Fitness level
Trackers use algorithms that consider these variables to provide a personalized calorie burn estimate. However, these algorithms aren’t perfect. The type of activity you do and how well the device detects intensity can affect the accuracy of calorie burn measurements.
For example, fitness trackers often provide more accurate data during high-intensity activities like running or cycling, where users can use heart rate data to make more precise calorie estimates.
On the other hand, activities like weightlifting, yoga or low-intensity walking may be harder for the device to measure accurately, leading to an over- or underestimation of your energy expenditure.
Some studies show that fitness trackers’ calorie burn estimates can vary significantly from actual calorie expenditure. In some cases, the error can be as large as 20 to 30 percent.
Measuring heart rate
Many devices now use optical sensors to measure heart rate by shining light through the skin and measuring the amount of light absorbed by blood vessels. This technique is called photoplethysmography (PPG), and it has become a standard method for tracking heart rate on fitness trackers.
Regarding measuring heart rate, fitness trackers are pretty accurate during steady-state activities like walking or running at a consistent pace. They may struggle to provide precise heart rate readings during more dynamic activities like weightlifting, high-intensity interval training (HIIT) or intense sports. This is because the wrist-mounted sensors can have difficulty picking up rapid changes in heart rate during quick movements.
Studies on heart rate monitoring accuracy in fitness trackers have yielded mixed results. Some devices, particularly high-end models, can measure heart rate within a few beats per minute (bpm) of the actual heart rate, while others may show larger discrepancies.
Overall accuracy
Devices that monitor health indicators offer a convenient and fairly accurate way to measure daily steps, calorie burn and heart rate. But the question remains – how accurate are fitness trackers?
While there are some inherent limitations in measuring these metrics with wearable devices, modern trackers do a good job of providing general estimates that can help users monitor their activity and make healthier decisions.
“Fitness trackers are not always 100 percent accurate. There are false positives, false negatives – they may indicate you have an arrhythmia when you really don’t. Those things can add extra anxieties to people who wear them,” Dr. Senfield says. “So, that’s where the caution comes in. If you don’t have any symptoms and you’re out of rhythm but you’re otherwise very healthy, the probability is very low you have something wrong. However, it does raise suspicion, and patients can show up in our office to get a better diagnosis.”
As technology advances, the accuracy of fitness trackers will continue to improve, but for now, they remain a useful tool for anyone looking to stay active and engaged with their fitness goals.
How we can help
Navigating the world of fitness trackers can be overwhelming. Whether you’re using a tracker to count steps, monitor calorie burn or measure heart rate, understanding its strengths and limitations is key to setting realistic fitness goals.
However, using a fitness tracker should not replace discussing your health with your primary care provider.
“We’re living in a time when technology is advancing at a very rapid pace. If a patient never knew they had a problem, these devices may get them to the office to get everything figured out. So, it’s very helpful for a patient who finds an abnormality and wants to discuss that concern with a primary care doctor or cardiologist,” Dr. Senfield says. “It’s not an uncommon thing to see someone in the office from a result on a fitness tracker. However, 95 percent of the time, the abnormality found on the fitness tracker is not a real arrhythmia. It does raise suspicion, though, especially if the result is raised repeatedly. Bottom line, it never hurts to get a professional’s opinion.”
Whether you’re considering a new exercise regimen or want to improve your overall health, reach out to your provider to ensure any changes you make are right for you.
Learn about the heart and vascular services we offer at Bon Secours.
