Worldwide sales of fitness trackers have increased from US$14 billion in 2017 to over $36 billion in 2020. The manufacturers of these devices want the consumers to believe that keeping a count of their steps and activity will promote a healthy lifestyle.
The analysis of research published over the past 25 years has suggested otherwise.
Professors of kinesiology – the science of human body movement – at Boise State, the University of Tennessee, and the University of North Florida have worked on this research. They analyzed more than two decades of research from several industrialized nations – all conducted before the COVID-19 pandemic.
They found 16 studies from eight different countries: Canada, the Czech Republic, Denmark, Greece, Japan, Norway, Sweden, and the United States. The studies were conducted between 1995 and 2017.
This research tracked samples of people from the same age group. For example, one Japanese study of physical activity among adults ages 20 to 90 collected data each year for 22 years from people in each age group.
Scientists tracked the participants’ physical activity using a variety of wearable devices, from simple pedometers – step counters – to more sophisticated activity monitors like accelerometers.
The study groups ranged from large, nationally representative samples numbering tens of thousands of people to small samples of several hundred students from a few local schools.
The ‘effect size’ for each study was calculated. The effect size is a method of adjusting the data to allow for an ‘apples-to-apples’ comparison.
These include the average physical activity at the beginning and end of each study, the sample size, and a measure of the variability in physical activity. Using a technique called meta-analysis, allowed them to combine the results of all studies to come up with an overall trend.
Researchers documented fairly consistent declines in physical activity, with similar decreases in each geographical region and in both sexes.
Overall, the decrease in physical activity per person was over 1,100 steps per day between 1995 and 2017.
Our most striking finding was how sharply physical activity declined among adolescents ages 11 to 19 years – by roughly 30 percent – in the span of a single generation.
Among adolescents, declines in physical activity were associated with increases in the use of smartphones, tablets, video games, and social media.
At school, most of the physical activity that adolescents perform has traditionally come from physical education classes. However, the changes in the frequency of physical education classes during the study period are inconsistent and vary from country to country.
All these factors may help to explain the decline in physical activity that we observed in our study.
Fitness trackers can help to increase people’s awareness of their daily physical activity. They are facilitators, rather than drivers, of behavior change.
The first step to increasing active movement is to measure it, which these devices can do. But successfully increasing one’s overall physical activity requires several additional factors such as goal setting, self-monitoring, positive feedback, and social support.