More Minutes, Fewer Steps: Hourly Associations Between Adolescent Smartphone Use and Physical Activity

Many adolescents do not meet the recommendations for adequate daily physical activity. Given adolescents' high use of digital technologies such as smartphones, digital technology is often a source of blame for these low levels. Specifically, it is suggested that time spent on digital technology is displacing time spent engaging in physical activity. However, existing research is inconsistent, and rigorous methodologies using objective measurements are needed to test fine-grained associations between digital technology use and physical activity.

The current research examines hourly associations between objectively recorded smartphone use and Fitbit-assessed step counts among late adolescents (N = 67; 58% female, M_age = 16.45). Smartphone screen time (i.e., time spent using one's phone) and pickups (i.e., frequency of phone engagement, such as through unlocks) were examined.

In support of the displacement hypothesis, when adolescents recorded greater smartphone screen time relative to their own average in a given hour, they took fewer steps in that hour. Conversely, when adolescents recorded greater pickups relative to their own average in a given hour, they took more steps in that hour.

There is evidence for a displacement effect for smartphone screen time and physical activity; however, this is not the case for pickups. Future research is needed to determine the role of context and individual differences.