Marc A Adams (marc.adams@asu.edu)
William D Johnson (William.Johnson@pbrc.edu)
Catrine Tudor-Locke (Catrine.Tudor-Locke@pbrc.edu)
Abstract
Background
An evidence-based steps/day translation of U.S. federal guidelines for youth to engage in ≥60
minutes/day of moderate-to-vigorous physical activity (MVPA) would help health
researchers, practitioners, and lay professionals charged with increasing youth’s physical
activity (PA). The purpose of this study was to determine the number of free-living steps/day
(both raw and adjusted to a pedometer scale) that correctly classified children (6–11 years)
and adolescents (12–17 years) as meeting the 60-minute MVPA guideline using the 2005–
2006 National Health and Nutrition Examination Survey (NHANES) accelerometer data, and
to evaluate the 12,000 steps/day recommendation recently adopted by the President’s
Challenge Physical Activity and Fitness Awards Program.
Methods
Analyses were conducted among children (n = 915) and adolescents (n = 1,302) in 2011 and
2012. Receiver Operating Characteristic (ROC) curve plots and classification statistics
revealed candidate steps/day cut points that discriminated meeting/not meeting the MVPA
threshold by age group, gender and different accelerometer activity cut points. The Evenson
and two Freedson age-specific (3 and 4 METs) cut points were used to define minimum
MVPA, and optimal steps/day were examined for raw steps and adjusted to a pedometerscale to facilitate translation to lay populations. Results
For boys and girls (6–11 years) with ≥ 60 minutes/day of MVPA, a range of 11,500–13,500
uncensored steps/day for children was the optimal range that balanced classification errors.
For adolescent boys and girls (12–17) with ≥60 minutes/day of MVPA, 11,500–14,000
uncensored steps/day was optimal. Translation to a pedometer-scaling reduced these
minimum values by 2,500 step/day to 9,000 steps/day. Area under the curve was ≥84% in all
analyses.
Conclusions
No single study has definitively identified a precise and unyielding steps/day value for youth.
Considering the other evidence to date, we propose a reasonable ‘rule of thumb’ value of ≥
11,500 accelerometer-determined steps/day for both children and adolescents (and both
genders), accepting that more is better. For practical applications, 9,000 steps/day appears to
be a more pedometer-friendly value.
Sem comentários:
Enviar um comentário