Table 1.

Sample characteristics and days per week of physical activity among the 2012 NHANES National Youth Fitness Survey participants

	6-9 y	10-12 y	13-15 y	Full sample (6–15 y)
	n = 491	n = 379	n = 354	n = 1224
Subject Charateristics	% of sampleb	% of sampleb	% of sampleb	% of sampleb
Sex
Female	47	50	50	49
Race/Ethnicity
non-Hispanic White	52	54	55	54
non-Hispanic Black	14	12	15	14
Hispanic	22	24	22	23
Other	11	10	8	10
Weight Statusc
Underweight	3	4	3	3
Normal Weight	65	53	61	60
Overweight	14	25	17	18
Obese	19	19	20	19
Days of Physical Activity per Weeka
0 days	2	5	7	4
1-3 days	10	19	29	18
4-6 days	26	32	40	32
7 days	62	43	24	46
Mean (95 % CI) (Days)d	5.9 (5.7 – 6.1)***	5.1 (4.8 – 5.3)	4.4 (4.2 – 4.6)	5.2 (5.0 – 5.4)

^aPhysical activity was self- or proxy reported as the number of days that the child was physically active (increased heart rate or breathing hard some of the time) for a total of at least 60 minutes in the past 7 days)

^bNationally representative estimates taking into account the survey design of the 2012 NNYFS

^cWeight status of children were based on BMI-for-age percentiles

^dA linear trend across the three age categories for average days of physical activity was tested using a simple linear regression model accounting for the survey design of the 2012 NNYFS

***Indicates a significant regression coefficient for a linear trend (p < 0.001) across the three sub age groups