Translating physical activity recommendations for overweight adolescents to steps per day.
BACKGROUND
Steps/day guidelines for children aged 12 years and under are 12,000 to 16,000. There are limited reports in the literature on how many steps/day adolescents need to meet the 60-minutes/day moderate-to-vigorous physical activity (MVPA) recommendation. This study aimed to determine the steps/day that correctly classifies adolescents as meeting the 60-minute recommendation using objective measures.


METHODS
This analysis used data from 40 overweight (BMI M=31.5, SD=5.3) adolescents enrolled between 2005 and 2006 in a study to lose weight. Participants were aged 11 to 16 years (M=13.2, SD=1.2), 70.0% girls, and 52.6% non-Hispanic white, 23.7% Hispanic, and 23.7% other race/ethnicity. Participants wore an Actigraph accelerometer for up to 7 days that measured accelerations and step counts simultaneously. The age-adjusted Freedson equation was used to estimate physical activity-intensity minutes. Two criteria were used to define MVPA (3/6 and 4/7 METs). Analyses were conducted between 2008 and 2009.


RESULTS
Based on accelerometer data, approximately 48% and 10% of adolescents met the MVPA recommendation depending on the MVPA criteria. Adolescents who met phyiscial activity recommendation had higher MVPA min/day (p<0.001) and higher step counts (p<0.001), after adjusting for gender, age, and ethnicity. Receiver operating characteristic (ROC) curve analyses found that 9930 steps produced 0.84 sensitivity and 0.81 specificity (area under the curve [AUC] =0.89) and 11,714 steps produced 0.75 and 0.81 specificity (AUC=0.94) for meeting the recommendation using the 3/6 and 4/7 criteria, respectively.


CONCLUSIONS
Depending on the MVPA criteria used, these data suggest that overweight adolescents are likely to meet national MVPA recommendations if they accumulate between 10,000 and 11,700 steps per day.
Adams
Marc A
MA
Joint Doctoral Program in Public Health, San Diego State University/University of California, San Diego, California, USA. madams@projects.sdsu.edu
Caparosa
Susan
S
Thompson
Sheri
S
Norman
Gregory J
GJ
D000293:Adolescent; D019540:Area Under Curve; D002648:Child; D015444:Exercise; D005260:Female; D006293:Health Promotion / Q000379:methods; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic; D009043:Motor Activity / Q000502:physiology*; D050177:Overweight; D012372:ROC Curve; D016138:Walking / Q000502:physiology / Q000706:statistics & numerical data*; D015431:Weight Loss / Q000502:physiology