Adequate sleep and physical exercise are cornerstones of a healthy lifestyle. In 2023, only about a quarter of high school students in the U.S. met the guideline for daily exercise, and another recent survey found over 75% of adolescents do not get the recommended amount of sleep per night.
A new study by researchers at the University of Minnesota School of Public Health examined how sleep contributes to sedentary behavior and overall activity levels in teens. The study, published in the Journal of Physical Activity and Health, suggests when teens sleep longer, and at times better aligned with their biological clocks, they are more likely to engage in physical activity.
Researchers reviewed data from 260 ninth-grade students in Minnesota. All student participants wore activity trackers continuously for seven days, allowing researchers to objectively measure sleep duration, sleep timing, sleep efficiency and physical activity levels - including sedentary time, light physical activity, and moderate to vigorous physical activity. The team also included demographic factors such as sex, race and parental education levels. They found:
- Longer sleep was associated with less sedentary time. For each additional hour of sleep, adolescents spent about 26 fewer minutes sedentary on weekdays and 19 fewer minutes sedentary on weekends, suggesting that extra sleep time may replace inactivity during the day.
- Closer alignment with adolescents' natural circadian rhythms - also known as the internal clock - was linked to higher activity levels. Shifting to a later sleep schedule was linked to higher levels of physical activity across all categories.
- More time spent sleeping was not associated with reduced activity levels. Sleep duration was not related to time spent doing moderate to vigorous physical activity on either weekdays or weekends, suggesting that increased sleep did not come at the expense of exercise.
"There's a common fear that if teens sleep more, there will be less time for them to be active," said Kayla Johnson, a researcher at the School of Public Health and lead author. "Our results suggest the opposite. The kids that are sleeping more are also the kids that are spending less time sitting around on the couch."
Future research will explore how sleep and physical activity behaviors develop over time, how these behaviors vary across populations, and other factors that could influence these patterns.
About the School of Public Health
The University of Minnesota School of Public Health improves the health and wellbeing of populations and communities around the world by bringing innovative research, learning, and concrete actions to today's biggest health challenges. We prepare some of the most influential leaders in the field, and partner with health departments, communities, and policymakers to advance health equity for all. Learn more at sph.umn.edu.
