How accurate are wearable fitness devices? Featured Image

How accurate are wearable devices for measuring activity data?

There is an old saying “that which gets measured, gets improved!” This couldn’t be closer to the truth!! However, how do you know what is the best way to measure, what to measure, and what is accurate? Is my heart rate watch tracking my calories accurately? Did I really burn that many calories on the elliptical? Do I really need to do 50 burpees to burn “X” amount of calories? Well, there is some truth to these and a lot of variables that cause errors and inaccuracies.

It is important to track your measurements whether its weight loss, fat loss, lean muscle mass gains, strength gains, improved resting heart rate, blood pressure, blood sugar, lipid levels, and any other numerous measurable metrics.  Tracking serves as a baseline to determine if your program is working or needs adjusting. Tracking also helps determine if you are really working as hard as you should be or perhaps you have been slacking. Tracking also helps bring other underlying issues to the surface, such as hormonal imbalances or other endocrine problems and even disease. If you are diligent with proper tracking and you measure your activity, food, and results but find that you are still struggling with losing weight this might be due to an underlying thyroid condition or any other numerous health complications.

How do these devices work?

Some of them work based off of heart rate, some work off of electrical currents, some work off of heat sensors, or even movement sensors. Other measurable devices also ask for programming of body statistics such as height, age, weight, sex, and even body fat percentage. The more data the device measures and the more statistics you are required to enter then the more accurate data it will produce.

It is important to find a device that you can wear all day and night for at least a week or so. Wearing a device while you sleep and throughout the 24 hours of activity will give you more accurate insight into exactly how many calories you burn and in particular with specific activities. You may not find a water proof device and therefore you would simply take it off for the few short 10-15 minutes or so that you are actually in the shower. Then immediately put the device back on and continue to wear all day. I would recommend this for at least 1 week so you track your trends. Some days you might find your more active than others such as workdays verses weekends. I would log your results from each day. How many calories burned each day, steps taken if available or distance traveled, average heart rate, etc. Then at the end of 7 days, I would average these out to get a general idea of what your average measurement is for all of these metrics. This will give you a good baseline to build a exercise or nutrition program off of.

How accurate are these devices?

As we mentioned earlier some device are obviously more accurate than others and this goes for all types of devices. Heart rate monitors vary, calorie trackers vary, and even body fat analysis devices vary in accuracy. In a study done with 40 people (47% male, and 53% female) they tested 9 wearable devices; the ActiGraph GT3X+, activPAL, Fitbit One, GENEactiv, Jawbone Up, LUMOback, Nike Fuelband, Omron pedometer, and Z-Machine. The devices were tested over a period of 24 hours of activity including sleep, sedentary, low, moderate, and high activity. These devices were tested for accuracy and percent of errors and the closest measurements equivalent to standards in each activity level sleep, sedentary, low, moderate, and high activity. The results were shocking. Error rates ranged from 8.1% to 16.9% for sleep, 9.5% to 65.8% for Sedentary, 19.7% to 28.0% for Low Physical Activity, and a shocking 51.8% to 92% for Moderate to Vigorous Physical Activity, and 14.1% to 29.9% for Steps. Equivalence testing indicated that only were significantly equivalent to standards: the LUMOback for Sedentary Activity and the GT3X+ had the closest measurement for sleep and steps. The GENEactiv was the closest for Low Activity and the Fitbit for Moderate to Vigorous Activity. It is important to note that the high error percentage for moderate to vigorous physical activity ranges from 52-92% inaccurate! This means that most people who are pretty active in their lifestyles could be potentially have an extremely inaccurate measurement of true heart rate, calories burned, steps taken, or distance traveled. It is great to keep this in mind when building your workout or nutrition program. Do not rely solely on 1 device and do not rely heavily on it to guarantee your results. As the old saying goes “don’t put all your eggs in 1 basket, so to say.”

In conclusion, currently, no device accurately measures activity data across the entire 24 hour day, but in the future of activity measurement we should aim for more accurate 24 hour measurement as a goal. More research is needed on the accuracy of the devices at certain activity levels and certain body types. When selecting a device to use, it is best to select a device based on your outcome interest.

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