Physical Activity Levels of High School Students—United States, 2010 FREE

MMWR. 2011;60:773-777

1 table omitted

Healthy People 2020 (HP 2020), released in December 2010, outlines numerous public health objectives, including objectives for youth physical activity participation.¹ HP 2020 includes three objectives for meeting current federal physical activity guidelines for (1) aerobic physical activity (participation in ≥60 minutes of aerobic activity per day, 7 days per week) (PA 3.1); (2) muscle-strengthening activity (muscle-strengthening activities on ≥3 days per week) (PA 3.2); and (3) aerobic physical activity and muscle-strengthening activity combined (PA 3.3).^1,s The HP 2020 target for PA 3.1 is 20.2%; targets for PA 3.2 and PA 3.3 are not set because baseline data are not available. To meet the HP 2020 targets for physical activity, promotion of physical activity among female high school students,³ high school students in upper grades,³ and youths with obesity⁴ might be warranted, given that these subpopulations are at risk for low levels of physical activity. To determine the proportion of U.S. youths who meet these HP 2020 objectives, CDC analyzed data from the 2010 National Youth Physical Activity and Nutrition Study (NYPANS), a school-based study conducted by CDC that included height and weight measurements and a survey that measured physical activity and dietary behaviors among a nationally representative sample of students in grades 9-12. This report summarizes the results of that analysis, which indicated that among students nationwide in grades 9-12, 15.3% met the aerobic objective, 51.0% met the muscle-strengthening objective, and 12.2% met the objective for both aerobic and muscle-strengthening activities. To improve youth physical activity participation, efforts are needed among CDC, state and local public health agencies, schools, and other public health partners that promote physical activity.

NYPANS measured the prevalence of behaviors and behavioral determinants related to physical activity and nutrition. The survey used a three-stage cluster sample design to obtain cross-sectional data representative of public- and private-school students in grades 9-12 in all 50 states and the District of Columbia. Students completed an anonymous, self-administered questionnaire in their classrooms during a regular class period in the spring of 2010. Data from 11,429 students were available for analysis. The school response rate was 82%, the student response rate was 88%, and the overall response rate* was 73%. Trained data collectors also measured students' height and weight using a standard protocol. A total of 1,728 respondents with missing data on sex, grade, race/ethnicity, height, weight, or physical activity were excluded, resulting in a final sample of 9,701 students.

To assess aerobic physical activity, students were asked, “During the past 7 days, on how many days were you physically active for a total of at least 60 minutes per day? (Add up all the time you spent in any kind of physical activity that increased your heart rate and made you breathe hard some of the time.)” Response choices ranged from 1 to 7 days. To assess muscle-strengthening activity, students were asked, “On how many of the past 7 days did you do exercises to strengthen or tone your muscles, such as push-ups, sit-ups, or weight lifting?” Response choices ranged from 0 to 7 days. Body mass index (BMI) was calculated from measured weight and height (weight [kg]/height [m²]) and classified as under/normal weight, overweight, or obese based on sex-specific and age-specific reference data from the 2000 CDC growth charts.†

Students met the HP 2020 physical activity objectives¹ if they met current federal physical activity guidelines for (1) aerobic physical activity (participation in ≥60 minutes of aerobic activity per day, 7 days per week) (PA 3.1), (2) muscle-strengthening activity (muscle-strengthening activities on ≥3 days per week) (PA 3.2), and (3) aerobic physical activity and muscle-strengthening activity (participation in ≥60 minutes of aerobic activity per day, 7 days per week and muscle-strengthening activities on ≥3 days/week) (PA 3.3). Data were weighted to provide national prevalence estimates and were examined by demographic characteristics (sex, grade, and race/ethnicity) and BMI category. Statistical software was used to account for the complex sampling design and calculate prevalence estimates and 95% confidence intervals; t tests were conducted for pairwise subgroup comparisons, and linear and quadratic trends in grade and BMI category were tested. Because the numbers of students from other racial/ethnic groups were too small for meaningful analysis, race/ethnicity is reported only for non-Hispanic white, non-Hispanic black, and Hispanic students (who might be of any race). All differences presented in this report are statistically significant (P <0.05).

Nationwide, 15.3% of high school students met the HP 2020 objective for aerobic activity. A higher percentage of male (21.9%) compared with female (8.4%) students; 9th-grade (18.5%) compared with 10th-grade (15.3%), 11th-grade (13.3%), and 12th-grade (13.1%) students; white (16.9%) compared with Hispanic (11.8%) students; and under/normal weight (16.3%) and overweight (16.5%) students compared with those with obesity (10.7%) met the aerobic objective (Table).

Nationwide, 51.0% of high school students met the HP 2020 objective for muscle-strengthening activity. A higher percentage of male (65.0%) compared with female (36.6%) students; 9th-grade (55.6%) and 10th-grade (52.2%) compared with 12th-grade (46.4%) students; and under/normal weight (52.6%) and overweight (51.7%) students compared with those with obesity (45.2%) met the muscle-strengthening objective.

Nationwide, 12.2% of high school students met the HP 2020 objective for both aerobic and muscle-strengthening activities. A higher percentage of male (18.5%) compared with female (5.8%) students; 9th-grade (15.0%) compared with 10th-grade (12.3%), 11th-grade (10.7%), and 12th-grade (10.3%) students; white (14.1%) compared with black (9.7%) and Hispanic (9.9%) students; and under/normal weight (13.3%) and overweight (13.6%) students compared with those with obesity (7.3%) met the objective for both aerobic and muscle-strengthening activities.

Reported by: Janet E. Fulton, PhD, Dianna D. Carroll, PhD, Deborah A. Galuska, PhD, Div of Nutrition, Physical Activity, and Obesity, Sarah M. Lee, PhD, Danice K. Eaton, PhD, Nancy D. Brener, PhD, Div of Adolescent and School Health, National Center for Chronic Disease Prevention and Health Promotion; MinKyoung Song, PhD, EIS Officer, CDC. Corresponding contributor: MinKyoung Song, msong@cdc.gov, 770-488-5718.

CDC Editorial Note: The findings of this study indicate that approximately one out of 10 U.S. high school students met the HP 2020 objective for both aerobic and muscle-strengthening activities (PA 3.3). The low prevalence of meeting PA 3.3 is a function of the low percentage of students who met the objective for aerobic activity (PA 3.1), which might be attributable to the greater number of days and time needed to meet the aerobic activity recommendation compared with the muscle-strengthening activity recommendation. The prevalence of meeting the objective for both aerobic and muscle-strengthening activities (PA 3.3) was found to be lower among female students, students in upper grades, and students with obesity.

The most recent nationally representative self-report data for muscle-strengthening activity was collected in the 2003 national Youth Risk Behavior Survey (YRBS). The findings in this report are consistent with those from the 2003 YRBS,¹ with one exception: data from the 2003 YRBS indicated that white and Hispanic students have higher levels of muscle-strengthening activity than black students, whereas this report notes no statistically significant difference by race/ethnicity. With respect to estimates of aerobic activity, the findings in this report are consistent with those from the 2009 YRBS. Although the aerobic activity estimate (15.3%) from this report is lower than the 2009 YRBS (18.4%), the findings in this report showed patterns by sex, grade, and race/ethnicity that are consistent with the results of that survey.³

The findings in this report are subject to at least three limitations. First, the reliability and validity of responses to the aerobic activity and muscle-strengthening survey questions have not been determined, and underreporting or overreporting might have occurred (e.g., because of recall or social-desirability bias). However, studies among youths comparing self-reported physical activity levels to accelerometer readings have demonstrated acceptable correlations.^6,7 Second, NYPANS inadvertently did not include a “zero days” response to the aerobic question; therefore, more students might have reported some amount of aerobic activity than might have done so if a “zero days” response option had been offered. However, having no “zero days” response option likely did not affect the number of students who reported aerobic activity 7 days per week. Finally, these findings only apply to students who attended public and private high schools. Nationally, in 2008, approximately 4% of youths aged 16-17 years had not completed high school and were not enrolled in a high school program.⁸

This study serves as the first assessment of achievement of both aerobic and muscle-strengthening physical activity recommendations among a nationally representative sample of high school students, and its results justify the need to improve and increase efforts to promote physical activity among youths. Barriers to increasing youth physical activity participation include students' reluctance to participate because of low confidence levels in their physical abilities, lack of awareness of physical activity benefits, lack of family/peer support, lack of choices in physical education (PE) curriculum activities, and inadequate school/community facilities or resources for physical activity.⁹

CDC's Guide to Community Preventive Services‡ recommends evidence-based strategies to increase physical activity, such as enhancing school-based PE programs by increasing the length of classes or activity levels in PE classes. The guide also recommends creation of or enhanced access to places for physical activity combined with informational outreach activities about their location and availability. Additionally, the Youth Physical Activity Guidelines Toolkit§ provides specific strategies that schools, families, and communities can use to support youth physical activity.

These strategies are being included in programs such as the First Lady's Let's Move! campaign,∥ CDC's Communities Putting Prevention to Work program,¶ and the Safe Routes to School program.# Additionally, the National Physical Activity Plan** identifies the need to use a multisector approach involving schools, communities, families, and the private sector to facilitate integrated approaches to increasing population activity levels. Continued efforts to implement these evidence-based strategies and programs will help to meet the HP 2020 objective target for aerobic activity as well as the targets for muscle-strengthening activity and both aerobic and muscle-strengthening activities (once these targets have been set based on findings from the 2011 national YRBS). Public health efforts to improve participation in aerobic and muscle-strengthening activities among U.S. high school students might be most relevant for female students, students in upper grades, and students with obesity.

Prevalence of physical activity levels among U.S. youths has been examined over time, but data on the proportion of U.S. youths who meet Healthy People 2020 objectives have not been reported.

What is added by this report?

Based on data from the 2010 National Youth Physical Activity and Nutrition Study, among high school students nationwide in grades 9-12, 15.3% did ≥60 minutes of aerobic activity per day, 7 days per week, 51.0% did muscle-strengthening activities on ≥3 days per week, and 12.2% did ≥60 minutes of aerobic activity per day, 7 days per week and did muscle-strengthening activities on ≥3 days per week. Particularly, female students, students in upper grades, and students with obesity had lower rates of meeting the objective for aerobic and muscle-strengthening activities.

What are the implications for public health practice?

Along with federal efforts, multisectoral partnerships involving schools, communities, and the private sector might be necessary to increase both aerobic and muscle-strengthening activities among U.S. high school students, with a particular focus on female students, students in upper grades, and students with obesity.

REFERENCES

9 Available.

*Overall response rate = (number of participating schools/number of eligible sampled schools) × ([number of usable questionnaires] /[number of eligible students sampled]).

†BMI classifications: <85 percentile = under/normal weight, ≥85 and <95 percentile = overweight, and ≥95 percentile = obese.

‡Available at http://www.thecommunityguide.org/pa.

§Available at http://www.cdc.gov/healthyyouth/physicalactivity/guidelines.htm#1.

∥Additional information available at http://www.letsmove.gov.

¶Additional information available at http://www.cdc.gov/communitiesputtingpreventiontowork.

#Additional information available at http://www.saferoutesinfo.org.

**Available at http://www.physicalactivityplan.org.