How many steps did you take today? Are you sure? How do you know?
How do fitness trackers measure steps?
If you are one of the many people who use an exercise band or a smartwatch to count your steps, you may not realize an inescapable fact: they lie. The fact that they tell you that you have reached your daily goal does not mean that you have taken so many steps. The sad truth is that these devices can underestimate or overestimate the number of steps you take in a day. In fact, your counts may differ widely depending on the brand you are using.
Part of the reason is based on how they work. Today’s fitness bands use multi-axis inertial sensors called accelerometers to detect when the device is moving. Some also use gyros to determine the direction and rotation movement. Because these sensors generate so much data that the device driver must analyze and interpret them, the results can often be misunderstood and bad reports presented. In other words, what you see is not necessarily what you walk.
There may be several reasons for this.
When your exercise band interprets the data from your motion sensors, you are supposed to ignore movements that are not associated with gait. However, it is not always successful. For example, hitting the nails with a hammer can create vibrations that can be close enough to make passing movements that the data is misinterpreted as walking.
More subtle movements can also cause errors. Washing your hands, preparing food, petting your cat or using a computer mouse can also cause your device to record steps. The use of vibrating devices, such as a random orbital sander that you would use in a carpentry project, can make your tracker record hundreds of steps in just a few minutes.
However, not only intentional movements can be misunderstood. Vibrations that affect all or part of your body can also cause inaccurate step counts. For example, traveling in a car, bus, train or subway can create movements that are interpreted as steps. You can add hundreds of steps while driving your car for an hour or less.
Because most trackers measure when you climb stairs or a slope, they use a combination of motion sensors and sensors that detect air pressure. As it rises, the air pressure decreases. Unfortunately, changing air pressure levels can also confuse your tracker’s count of the number of flights you have climbed.
For example, traveling in an elevator can be registered as climbing stairs. Changes in air pressure when traveling in a car or other moving vehicle can divert the account, as well as entering and leaving high-rise buildings that have an air pressure that is different from the outside. Even rapid changes in the weather can be recorded as climbing floors.
HOW TO KEEP YOUR NUMBERS ACCURATE
Therefore, trackers are not perfect for counting steps taken or flights uploaded. But you don’t need perfect accuracy to know if you have taken more or fewer steps today than yesterday. There are several things you can do to make sure you get the most accurate readings possible.
The most important first step (so to speak) to make sure your device is as accurate as possible is to read the manual. Follow the manufacturer’s instructions carefully when setting up the device and when using it. Making sure you are using the tracker correctly is more likely to result in an accurate count.
USE YOUR NONDOMINANT HAND
Many trackers request that you specify whether you are using the device in your dominant or non-dominant hand. Your dominant hand is likely to be more active, whether you are handling a tool or stirring a pot, so there will be more opportunities to make mistakes. Even if your tracker’s instructions do not cover this, consider using your device in your non-dominant hand.
Be sure to use the device so that it fits firmly on your wrist. Some people do not like a tight fit for their watch or bracelet, but if your gym band collapses on your wrist, you are likely to get a counterfeit step count. (A loose fit can also prevent heart rate sensors and other functions from working properly.)
LOG YOUR NON-ACTIVE TIMES
If you like the details, record your counts of previous and subsequent steps when you spend a long period of time sitting or doing some other activity that does not involve walking. You can then deduce these false steps from the total score of your day. This will also give you a measure of how many of these misunderstood steps occur during a typical day. You can also remove the tracker before starting activities that you know will generate false results, such as using a sander or playing a musical instrument.