The statement best supporting the assumption that the author has conducted research on this topic is:
"Yet according to the Center for Disease Control (CDC), physical activity in adolescents improves strength and endurance, helps build strong bones, reduces stress, increases self-esteem, and it is also known to increase brain function."
This response indicates that the author is referencing authoritative research from a credible source (the CDC), which implies that they have engaged in research to back up the claims made in the text.