Teens at risk of developing diabetes can prevent or delay its onset through strength training exercise, a University of Southern California study has found.

Research led by Michael Goran, PhD, professor of preventive medicine in the Keck School of Medicine of USC, showed that overweight Latino teenage boys who lifted weights twice per week for 16 weeks significantly reduced their insulin resistance, a condition in which their bodies don't respond to insulin and can't process sugars properly. Insulin resistance is common in obese children and is a precursor of diabetes.

Previous research has demonstrated that aerobic and resistance exercise is effective in improving insulin sensitivity in adults, but no controlled studies of resistance exercise had been done on overweight youth. Goran and colleagues hypothesized that overweight teens would be more likely to stick with a resistance training regimen compared to aerobic exercise because it is less physically taxing and gives visible results quicker.

The researchers chose to focus on Latino teens because they are at particular risk for diabetes. About half of all Latino children born in 2000 are expected to develop type 2 diabetes in their lifetime, according to the Centers for Disease Control.

Twenty-two boys aged 14 to 17 lifted weights two times a week on gym equipment guided by personal trainers. The trainers used increasing resistance and fewer repetitions as the participants improved. While there was no change in their total body fat mass, the percent body fat significantly decreased and lean muscle mass increased in the resistance-training group compared to the control group. Ninety-one percent of the weight-lifting participants also significantly improved their insulin sensitivity.

"This shows that lifting weights is a good form of exercise that overweight teens can excel at and benefit from," said Goran, who is also associate director of the USC Institute for Health Promotion and Disease Prevention Research. "Whether they lose weight or not is not important – they still benefit by increasing muscle mass," he says.

Goran's research group is working on developing a home exercise routine that teens could do with exercise bands and hand weights.

Based on the results from this study, funded in part by the Thrasher Research Fund, Goran is now conducting a larger study of the same type. That project is funded by the National Institutes of Health, and has begun recruiting overweight Latino and African-American girls and boys aged 14 to 18. That research will also incorporate nutrition education to some of the participants.

The findings were published in the July issue of Medicine and Science of Sports Exercise.

Academic Achievement Higher Among Most Active Kids: Vigorous Physical Activity Linked To Better Grades.

Children who participate in vigorous physical activity, such as sports, perform better in school, according to a new study released by the American College of Sports Medicine (ACSM).

The most active kids more often have better grades, found the examination of activity and physical education (PE) compared to academic achievement.

The link between activity and academic performance was most significant when kids met Healthy People 2010 (HP2010) guidelines for vigorous activity 20 minutes a day, at least three days a week. Grades were not affected among kids who were moderately active for 30 minutes at least five days a week, the study researchers found.

The study was conducted to determine the effect of physical education class enrollment and overall physical activity on academic achievement.

Some 214 middle school-aged students participated, all of whom were randomly assigned to a PE course for either the first (August to mid-January) or second (mid-January to June) semester of the academic year. The research team measured students' physical activity in and outside school in 30-minute blocks, and compared their individual grades in core subjects, such as English, world studies, science and mathematics.

"Physical education and activity during the school day may reduce boredom and help keep kids attention in the classroom," said Dawn Podulka Coe, Ph.D., the study's lead author. "We were expecting to find that students enrolled in PE would have better grades because of the opportunity to be active during the school day. But, enrollment in PE alone did not influence grades. The students who performed better academically in this study were the most active, meaning those who participated in a sport or other vigorous activity at least three times a week."

Most of the vigorous activity was achieved outside the classroom, in sports such as soccer, football, basketball and baseball/softball. Since academic performance was favorably influenced by this level of activity, the researchers suggest incorporating vigorous activity in PE classes.

"This is a good tool for all of us — parents, teachers and researchers alike — to understand what motivates students and possibly coordinate their activity and academic needs," said Coe.

The study was published in the August issue of Medicine & Science in Sports & Exercise®, the official journal of ACSM. The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world.

For more information on the American College of Sports Medicine, visit www.acsm.org.