Teenage girls perceive lack of time as the number one barrier to physical activity, according to a new study from the American College of Sports Medicine.

The three-year survey assessing black and white adolescent girls reveals sedentary habits are mostly linked to internal barriers (interest, motivation), which were unrelated to external factors (jobs, recreation).

More than half of approximately 2,000 girls surveyed from ages 16 or 17 to 18 or 19 were identified as being sedentary. Of those classified as sedentary (about 1,000 girls), the majority (65 percent for black girls and 80 percent for white girls) claimed lack of time was their primary barrier to activity, the study authors reported. They also frequently said they were too tired or uninterested in participating in physical activities. Other commonly reported barriers, such as safety and body image concerns, came from the 10-item questionnaire developed to assess the girls' perceptions of barriers to activity participation.

With the identification of these barriers, researchers corroborated with other information about the girls to understand whether barriers were simply perceived or were related to external circumstances. For instance, while the majority of girls felt lack of time prevented their pursuit of activity, researchers found no difference in hours at work or in household chores when compared to girls who did not report time as a barrier. Further, girls who said they were too tired had about the same amount of sleep per night as those who did not report fatigue.

"Overall activity levels have declined by 83 percent in these age groups," said Dr. Sue Y.S. Kimm, M.P.H., lead author of the study. "These girls are definitely at risk for becoming overweight or obese, if they are not already, because of this steep decline. Recognizing what these girls perceive as barriers to their health and wellness can help us motivate them to find balance in their life that includes an increase in energy expenditure."

Other findings from the study showed habitual physical activity was significantly lower among black girls; these girls spent twice as much time watching television or videos and were significantly heavier than white girls. More white girls reported lack of time, and also were significantly more likely to indicate fatigue and self- consciousness as a barrier to exercise. Black girls were more than twice as likely to cite safety as a concern, although this was not one of the leading barriers to activity participation. Researchers were interested to find that black girls cited fewer barriers overall, and suggested the greater decline in activity participation may reflect cultural differences and attitudes about exercise.

"We don't know as much as we'd like about why girls become particularly inactive during adolescence," said Kimm. "Our evidence suggests the two most commonly cited reasons –- lack of time and fatigue –-are probably not actual barriers because these girls did not work more hours after school or have less sleep than others. However, it's the perception of a barrier we must overcome in order to help these girls find the time and energy it takes to get moving."

ACSM and the U.S. Centers for Disease Control and Prevention recommend 30 minutes of physical activity on most, if not all, days of the week. For those who perceive lack of time as a major barrier, health and fitness experts agree physical activity can be accumulated during the day in shorter periods of activity, such as 10- or 15-minute bouts.

The results of the study were published in the March issue of Medicine & Science in Sports & Exercise, the journal of the American College of Sports Medicine (ACSM).

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