Welcome to ‘Kagoo Explains’ - a series of short articles de-mystifying some of the confusing terminology used to describe tech. Today we’re looking at step tracking - how smartphones use sensors to quantify every step you take.
Smartphones have so many benefits: they provide constant communication, a portal to the endless info on the Net, and a welcome distraction when bored. One extremely helpful feature of modern smartphones is their ability to measure how much you are moving. This function is known as *Step Tracking*.
Unsurprisingly, step tracking is the act of detecting and counting the number of steps you take every day. This makes it helpful as a broad indicator of how active you are, or how much you’re sitting on your arse every day. The idea is that the more steps you take, the more you’re exercising your body, so the healthier you will be.
This isn’t a perfect metric - there is a lot of exercise you can do that won’t be tracked by step counting, such as rowing or weightlifting - but it’s the perfect match for a smartphone, since most people have their phone in a pocket when they leave the house. While originally you needed a dedicated pedometer to measure your movement, advances to smartphone sensors and algorithms over the last decade have made every phone into a reasonably-accurate pedometer!
How many steps should you take in a day?
It’s a reasonable question: how many steps is ‘enough’ for a day? For a long time, 10,000 steps has been the magic number - do that many and you’re staying active enough to be healthy. However it appears that number originated in a marketing campaign for the 1964 Olympics in Tokyo , rather than from any scientific study.
Since that point, more comprehensive studies have been carried out, and found that the optimal step count is lower - between 5,000-7,500 steps per day is a good average, while the long-term benefits plateaued above 7,500 steps. So if you’re not hitting the magic 10k, don’t worry too much - as long as you’re getting a good amount of steps in, you’ll see a health benefit.
Every Step You Take...
Your smartphone tracks your steps primarily through use of a sensor called an ‘accelerometer’. This - as the name suggests - is a device designed to measure acceleration. When placed inside a smartphone it allows the device to detect a variety of motions, such as the phone being dropped or turned.
How does this help your smartphone measure steps? Well as you walk, the movement of your legs jostles your phone in your pockets or handbag in a regular motion. Even if the phone is being held still, your body is still in motion, so the movement will be detected. The accelerometer detects this regular movement, and translates each ‘bounce’ of the phone as a step.
This is obviously a *massive* oversimplification - there is a lot more going on behind the scenes. The individual ‘bounce’ of a step will differ between individuals, and can vary a lot depending on where your phone is being carried, whether you’re running or walking and how fast you’re going. To create the most accurate readings possible, modern smartphones rely on a number of different factors apart from the pure accelerometer data, such as:
Personal details: Many phones and health apps will ask for your gender, age, height and weight when you start using them. Some may even ask you to measure your ‘gait length’ - how far you travel in a single step. All of this data can be used to tweak the algorithms that govern the tracking to help improve results.
GPS: By looking at the GPS data for the period tracked, the phone can get a more accurate idea of the distance you’ve travelled. This allows them to better compute the number of steps by calculating how fast you’re moving (distance/time) and extrapolating the number of steps from that.
Machine Learning: Newer smartphone models use machine learning (where algorithms improve themselves through experience) to analyse where the system has previously correctly identified the steps taken, and uses that to tweak and improve itself in the future.
Average statistics: Not the most high-tech of solutions, but when lacking any other sources of information, the step tracker will fall back on reasonable assumptions of stride length, speed, weight, etc based on the averages for user’s age and gender.
Every Move You Make...
By pulling together multiple data sources and making some, the step tracker is able to reasonably judge the number of steps in your lunchtime walk and see whether you’re moving about, or sitting still binge-watching ‘The X-Files’ all day.
It’s important to note that phone step counters aren’t perfect [https://www.news-medical.net/health/How-do-wearable-fitness-trackers-measure-steps.aspx] - there are a number of limitations to the system. Because most smartphones rely on educated guesses from several disparate data sources, they aren’t 100% accurate. Any assumptions made about the user’s vital stats are bound to fall down occasionally, leading to inaccurate measurements. Moreover the system is prone to false positives - shaking your phone around while sitting down may register steps, as may a particularly bumpy train or bus ride.
For a far more accurate result, you would want to look at a dedicated pedometer such as a Fitbit. Many of these are worn around the wrist, and have a fleet of sensors designed specifically for step tracking. These offer far greater accuracy than a smartphone - being wrist mounted means less inaccuracy from bags or jostling, and the best ones come with a dedicated GPS module for distance tracking.
The biggest problem of a dedicated pedometer is that you don’t have it with you at any moment - it’s another gadget to buy, and one more thing to remember to put on in the morning. This is the real power of a smartphone pedometer - while it may not have perfect accuracy, it offers a constant track of your movement levels with minimal thinking. For many people, that is good enough - especially in these strange housebound times we live in, a constant reminder to move more is a welcome nag. Well… at least until something good comes up on Netflix.