Global sales of fitness trackers have grown from US$14 billion in 2017 to more than $36 billion in 2020. The meteoric success of these gadgets suggests that more people than ever are seeing value in keeping tabs on the number of steps they take, the stairs they climb, the time they spend sitting and the calories they burn. are burning.
The makers of these devices certainly want consumers to believe that tracking fitness or health-related behaviors will inspire them to increase their activity levels and make them healthier.
Our analysis of published research over the past 25 years suggests otherwise.
We are teachers of kinesiology – the science of human body movement – at Boise Statethe University of Tennessee and the University of North Florida. To find out if and how physical activity has changed in the years since fitness trackers first became popular, we analyzed more than two decades of research across multiple industrialized countries — all conducted before the COVID-19 pandemic.
Our systematic review of data from eight developed countries around the world shows that despite increasing sales of fitness trackers, physical activity has decreased from 1995 to 2017. Moreover, we found that this was not an isolated effect in one or two countries, but a general trend.
To conduct the study, we first looked for published research that tracked physical activity such as walking, household activities, or playing sports throughout the day. We wanted studies that get two “snapshots” of a population’s daily activity, with measurements at least a year apart.
We found 16 studies from eight different countries that met these criteria: Canada, the Czech Republic, Denmark, Greece, Japan, Norway, Sweden and the United States. The studies were conducted between 1995 and 2017.
It is important to note that these snapshots did not track specific individuals. Instead, they followed samples of people in the same age group. For example, a Japanese study of physical activity in adults aged 20 to 90 collected data annually for 22 years from people in each age group.
The 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 of tens of thousands of people to small samples of several hundred students from a few local schools.
After identifying the research studies, we calculated an ‘effect size’ for each study. Effect size is a method of fitting data to allow for an “apples to apples” comparison. To calculate the effect size, we used data reported in studies. These include the average physical activity at the start and end of each study, sample size, and a measure of variability in physical activity. Using a technique called meta-analysis, this allowed us to combine the results of all the studies to arrive at an overall trend.
We found that overall, the researchers documented fairly consistent declines in physical activity, with similar declines in each geographic region and in both genders. Overall, the decrease in physical activity per person was more than 1,100 steps per day between 1995 and 2017.
Our most striking finding was the steep decline in physical activity among adolescents aged 11 to 19 – by around 30% – within a single generation. For example, when we compared studies reporting physical activity in steps per day, we found that total steps per day per decade decreased by an average of 608 steps per day in adults, by 823 steps per day in children and 1,497 steps per day in adolescents. .
Our study does not address why physical activity has declined over the past 25 years. However, the studies we reviewed did mention some contributing factors.
More stares at screens, less walking or cycling
Among adolescents, declines in physical activity were associated with increased ownership and use of smartphones, tablets, video games, and social media.
In the United States, for example, screen time has increased dramatically among teenagers, from five hours a day in 1999 at 8.8 hours per day in 2017.
In school, most of the physical activity that adolescents do traditionally comes from physical education classes. However, the evolution of the frequency of physical education classes during the study period is inconsistent and variable from country to country.
All of these factors may help explain the decline in physical activity we observed in our study.
In addition, fewer adults and children walk or cycle to school or work than 25 years ago. For example, in the late 1960s, most American children between the ages of 5 and 14 ride a bike or walk to school. Since then, this “active transport” has largely have been replaced by car journeys. Rates of travel by school bus or public transit changed little.
So why use a fitness tracker?
So if physical activity levels have dropped at the same time as the popularity of fitness tracking has increased, what makes these gadgets useful?
Fitness trackers can help educate people about their daily physical activity. However, these devices are only part of the solution to solving the problem of sedentary lifestyles. They are facilitators, rather than drivers, of behavior change.
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When a person’s physical activity decreases, it opens the door to overall reduced levels of fitness and other health problems such as obesity or diabetes. On the other hand, physical activity has a considerable positive impact about health and welfare. The first step to increasing active movement is to measure it, which these devices can do. But successfully increasing overall physical activity requires several additional factors such as goal setting, self-monitoring, positive feedback, and social support.