Children's Cardiorespiratory Fitness Levels Lower with Increased Screen Time

INDIANAPOLIS – Cardiorespiratory fitness (CRF) levels could be increased in childhood if less time is spent in front of electronic screens, according to a study published in the official journal of the American College of Sports Medicine. This study, published in the June edition of Medicine & Science in Sports & Exercise®, shows an important negative effect of sedentary behavior in childhood.

The authors conducted a study to assess the relationship between time spent in screen-based sedentary behavior and changes in CRF. More than 2,000 children were followed from age 11 to 13, and each child self-reported their screen time and completed a shuttle run test to provide a measure of their CRF level. Importantly, the authors adjusted for time spent in high-intensity physical activity.

“In this technology age, children spend more time in sedentary behavior,” said the study’s lead author, Jonathan Mitchell, Ph.D., then at the Arnold School of Public Health, University of South Carolina. “We wanted to see if high screen-based sedentary behavior affected CRF levels in childhood, and if this effect was independent of physical activity levels.”

Children who reported more screen time completed fewer shuttle run laps between ages 11 and 13.  The association was strongest for the children who had mid-to-high CRF levels, and was independent of physical activity levels.  If instances of sedentary behavior are lowered in children, it is predicted that CRF levels would increase.    

“The results are interesting and add to the evidence that spending too much time sitting is hazardous to children’s health,” Mitchell added “If children limit the amount of time spent sitting in front of a screen, then this could help to combat declining levels of cardiorespiratory fitness in youth.”



The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. More than 45,000 international, national and regional members and certified professionals are dedicated to advancing and integrating scientific research to provide educational and practical applications of exercise science and sports medicine.

Medicine & Science in Sports & Exercise® is the official journal of the American College of Sports Medicine, and is available from Lippincott Williams & Wilkins at 1-800-638-6423. For a complete copy of the research paper (Vol. 44, No. 6) or to speak with a leading sports medicine expert on the topic, contact the Department of Communications and Public Information at 317-637-9200 ext. 133. Visit ACSM online at

The conclusions outlined in this news release are those of the researchers only, and should not be construed as an official statement of the American College of Sports Medicine.