December 6 — 7, 2007 Advisory Committee Meeting Minutes

Youth Subcommittee Report

Russell Pate, Ph.D., led the presentation from the Youth Subcommittee. The subcommittee was comprised of Dr. Howley, Dr. Yancey along with Steve Daniels, Chris Economos, Bob Gutin and Bog Malina as consultants. The CDC liaisons were Jackie Epping and Janet Fulton. The questions posed by the group included:

1. Among children and youth, is physical activity significantly related to body mass and composition, the metabolic syndrome, physical fitness, specifically cardio-respiratory fitness, muscular strength, mental health and bone health?

2. If there is a relationship is there a dose-response pattern?

3. Does age, gender or socio-economic status influence the relationship?

This area poses a large issue because the group is looking at many different outcomes and youth do not manifest themselves as a single group from a research perspective.

In terms of body mass composition a total of 104 studies were identified with varied designs. While there are complications in interpreting data from different study designs modest reductions in adiposity can be linked to physical activity. In general, 30 to 60 minutes of aerobic activity performed 3 to 5 times a week showed benefits.

For the metabolic syndrome, 41 studies were identified. Observational studies show that youth with high levels of physical activity have more favorable risk profiles. There is a clearer association in boy then in girls for insulin sensitivity. Some studies suggest that 360 minutes or 60 minutes per day, 6 days per week of moderate to vigorous activity shows beneficial impact on the metabolic syndrome.

Researching the relationship with regards to physical fitness, specifically cardio-respiratory fitness and muscular strength and endurance resulted in 34 studies. The studies consistently concluded that endurance training does produce increases in maximal aerobic power across both genders. Similarly, resistance training shows benefits in muscular strength.

The areas within mental health that were looked at include anxiety, academic performance, achievement, cognition, intelligence and self-perception. Tentatively, the group's findings show weak, inverse associations between activity and depression and anxiety. There is both little data and inconclusive data on the relationship on academic performance.

With regards to bone health, 29 studies were reviewed. From the data it appears there are positive effects of physical activity for bone mineralization. Conversely, there is a sense that physical inactivity during adolescence may result in children failing to meet their full potential for peak bone mass.

Finally, a compelling question is whether early patterns of activity during childhood influence health outcomes later in life. Currently, there is little literature on this point.