Table 1.

Study Variable Descriptions and Sources of Measurement.

Variable		Explanation	Grade
Enjoys PA		Mothers were asked to complete an interview called the “Parent Interview of Child Physical Activity.” This measure is a non-validated questionnaire with 13 items. One item was used for this study: “How much do you agree or disagree with the following statement: My child enjoys participation in physical activity/sports.” The response is a 5-point Likert scale: (1) strongly disagree, (2) somewhat disagree, (3) neutral, (4) somewhat agree, and (5) strongly agree.	5, 6
	SOFIT Percent MVPA	Researchers observed a PE instruction quality of the subjects using the System for Observing Fitness Instruction Time. The SOFIT is considered a more objective observation tool. Percent intervals in MVPA were computed as 100 times the sum of the number of intervals walking and very active divided by the number of intervals observed for cases with complete data.	5
	SOFIT PE Minutes Per Week	During the SOFIT observation, PE teachers were asked how many minutes per week the child participates in PE [29].	5
PE Minutes per Week MVPA		SOFIT percent MVPA was standardized and multiplied with the SOFIT Minutes per week to create an estimate of the minutes per week the subject spent in MVPA during PE classes.	5
	Physical Activity Monitor (PAM)	Computer Science and Applications, Inc. (CSA) single channel accelerometer. Monitors were worn by children for seven consecutive days throughout a typical school week. Average minutes per day of MVPA were calculated as: Moderate (3–5.9 METs) or Vigorous (6–8.9 METs), where: METs = 2.757 + (0.0015 × count) + (−0.08957 × age in years)+(−0.000038 × count × age in years) [12].	5, 6
Weekday MVPA		Total MVPA minutes attained during weekdays (Monday–Friday)	5
MVPA All Days		Total MVPA minutes attained during the entire week	6
Sport Self-Concept		Taken from the “How I Do in School” instrument. Five of the nineteen 7-point likert scale items pertain to sports. Example questions are “How good at sports are you?” and “How well do you expect to do in sports this year?”Mean of the 5 scores were totaled with higher scores, indicating a more positive self-concept of ability in sports. Reliability of the 5 items in the SECCYD dataset is Cronbach’s alpha = 0.85. Items were based on work from Eccles and Wigfield [30].	6
BMI		Subject’s height and weight were measured and recorded by researchers. Measurements were recorded in English standard measurement. In order to reduce measurement error, the English system BMI calculation was used: Weight(lbs)/Height(in)2 × 703	5, 6
Sex		Female or male sex—doctor identification at birth.	Enrollment
Limited Physical Functioning		Part of the Child Health Questionnaire completed by the subject’s mother. The questionnaire was designed to measure the mother’s perception of their child’s physical and psychosocial health. Limited Physical Functioning was computed as the mean of 4 items with higher scores indicating more physical limitations due to health problems during the previous 4 weeks [31].	5