Lifting weights may not sound like a typical activity for preteens. But perhaps it's something that more schools or communities may want to consider offering older children.
A recent study found that strength training twice a week increased the number of calories boys burned during regular physical activity.
No changes in calories burned were seen in girls who participated in twice-weekly strength training.
However, both boys and girls experienced improvements in their arm and leg strength after nearly five months of strength training.
While not available everywhere, strength training programs might be available through various community and school resources throughout the US.
This study, led by Udo Meinhardt, MD, of the PEZZ Center for Pediatric Endocrinology Zurich in Switzerland, looked at the effects of strength training in preteens.
The researchers randomly divided 102 Swiss boys and girls, aged 10 to 14, into two groups.
One group was assigned to participate in physical education classes twice a week for 19 weeks. During that same time period, the other group was assigned to a strength training program that met twice a week.
The researchers assessed how many calories the boys burned, their leg and arm strength and their body composition at the start and end of the 19 weeks. They did the measurements again three months after the project ended.
The groups had similar measurements, on average, at the start of the study.
However, the boys who participated in the strength training (but not PE classes) burned an average 10 percent more calories during their physical activity at the end of the 19 weeks.
There was no change in the girls' number of calories burned during physical activity in either group.
Both the boys and girls going through the strength training gained strength in their arms and legs.
The researchers did not find any other major differences between the two groups among the girls or the boys.
The researchers concluded that strength training in boys (but not girls) may increase how many calories they burn during physical activity.
"The less active children showed the greatest increase in spontaneous physical activity energy expenditure (calories burned)," the researchers wrote. "Girls showed a similar increase in strength, but not in spontaneous physical activity energy expenditure."
The researchers suggested that the girls may not have experienced the change in calories burned because they develop sooner in puberty.
"Strength training may be a promising strategy in schools to counteract decreasing levels of physical activity," the researchers wrote.
Strength training programs may not be available in many schools throughout the US. However, many cities have organizations that offer children an opportunity to participate in guided strength training.
These programs can exist at local YMCA centers or at Boys and Girls Clubs. They may also be a part of scouting programs or similar community programs.
This study was published November 4 in the journal Pediatrics. The study was funded internally, and the authors declared no conflicts of interest.