Last year $42Bn worth of trackers were sold globally, up by a factor of 4 since 2017. The market is forecasting double digit growth for the next decade. Half of the over 400m trackers sold are bought in the USA. Latest estimates suggest one in five Americans are using them. They are very fashionable. However, a third of people will stop using their tracker within 6 months and half will stop within a year. This is a marketing problem for firms. Is it a potential lost opportunity to improve health and wellbeing?
Personal fitness devices are becoming more and more sophisticated. They can be free standing or a twinned with your smartphone. They can track your performance, create trend graphs and even share your results with a community. But do they work? Will they improve your fitness, help you to lose weight, or improve your cardiovascular health?
What do they measure?
The first thing to say is that a cardiologist probably would not rely on them. Studies have compared trackers with medically derived estimates. They compared activity, heart rate and energy usage. They do not do very well, and their “accuracy” varies by manufacturer. The problem is partially with the sensors. Most trackers are based on an accelerometer and a heart rate monitor that shines light into the skin. The accelerometers allow the measurement of movement and are reasonable accurate. That movement has however then to be converted into steps etc. They are worse with walking rather than cycling or other activities. They work less well with men and if you have a high BMI.
The heart rate monitors are reasonably accurate. They do rely on light coming back from the skin. The “energy usage” report is different, it is a derived number. It needs data on age, weight and build. An algorithm then computes energy use. Unfortunately, it seems to have errors averaging closer to 30%. Increasingly tracker results are benchmarked with standards derived from medicine. Variations between devices therefore vary because of the sensors, the algorithms and the benchmarks.
But does that matter to individual users? It depends on how we use them. For many we do not use them as medical devices. We use them to track trends. When measurements are retaken, they seem to be about 80% accurate. The same distance walked will give the same number of steps with 80% accuracy. This was according to a recent study at Stanford University. They will be better at measuring changes or improvement.
They work better as part of a program
Most evidence shows that a fitness tracker will help. In a review of 390 different studies, a tracker added 1800 steps to the average daily total. On average they produce a 1Kg weight loss and 40 minutes extra daily activity. They will increase energy burnt. The studies show only small improvements with “second order” measures. Fitness is expected to affect many things, for example heart rate, weight and even depression. Most studies show an impact on fitness but a non-significant impact of the effects of fitness. Much of this might be due to the length of these studies. Many do not go beyond 3 months.
One of the biggest influencers of success in those 390 studies is whether the device is used as part of a bigger program. If an individual has a “behaviour change plan” then the tracker can help. Just putting on a watch has much less of an impact. This is hardly surprising since the objective is to encourage activity. Motivation is difficult to create with just a device.
At lot of the innovation in trackers is based on this idea. The manufacturers have an incentive to make your tracker indispensable. Sensor improvement will help but is not enough. It may in fact cause problems. A study by the American Heart Association showed that sophisticated sensors can cause anxiety. They found people monitoring irregular heartbeats with their new trackers. This was inducing anxiety and fixation.
You will keep on using your tracker only if it helps. Manufacturers are trying to recreate a behavioural change program without the trainers and fitness club. They are trying to make the watch self-sufficient. They have built in the capacity to set goals and track against them. They combine different readings to make them more relevant. They can compute a biological age as part goal and part “bragging rights”. Everybody needs a target. A biological age less than your chronological age seems to be motivating. After all we all feel younger than our age. They are creating online communities to motivate each other. For cyclists and runners, they will time how long it takes to climb a hill and how that compares with all the other people. Competition does motivate.
Trackers and Older People
Inactivity is one of the curses of the old. We know that exercise is good for mind and body. Can these trackers be used to motivate that activity? In ninety percent of cases the trackers appear to have helped. The success drops off as people get older. Beyond eighty it is less successful. People have lost muscle mass and bone density if they have not been exercising. It is even more difficult to encourage people to step count if they spend most of their day in a chair. Across all older age groups they have been used more successfully as part of a combined program. A program that requires a human leader. The earlier you start the more likelihood of success.
Fitness on Your Wrist
Will technology finally make fitness something you can wear on your wrist? Fitness trackers have come a long way since the first electronic pedometers produced in Japan. Those early innovators would not recognize the sophistication of todays trackers. What they did give us is the 10,000-step target. This was never medically derived. The manufacturer of one of those early devices needed a brand name. He realized that the Japanese character for 10,000 resembled someone walking. He used the character and the name for the brand launch ahead of the 1964 Tokyo Olympics. It stuck.