Study leader Lorraine Robbins of Michigan State University's College of Nursing said the study involved a racially diverse set of sixth-grade boys from two public middle schools who were brought together in seven focus groups.
The study, published in the Journal of School Nursing, found the main barrier for boys doing 1 hour of exercise daily was a lack of motivation, as well as environmental barriers such as a lack of equipment at schools and few neighborhood options with small yards and parks in disrepair.
The boys said they preferred playing computer or video games or watching TV rather than exercising, the researchers said.
"Although boys are more active, only a small percentage engages in 60 minutes of moderate to vigorous physical activity per day," Robbins said in a statement. "A lot of boys in both single- and dual-working parent homes care for themselves after school while their parents are at work. Many have limited opportunities for physical activity that are safe, accessible and affordable; this type of situation can lead to unhealthy eating habits."