Data for the analysis were the health related fitness scores, anthropometric measures, and physical activity information from the National Children and Youth Fitness Study. The subjects were 6,800 boys and 6,523 girls, ages 6 through 18. Multiple regression produced linear composites that were used as covariates to evaluate physical and environmental characteristics that relate to gender differences. The distance runs, chin-ups, and sit-ups displayed similar patterns in gender differences across age. Before puberty the important covariates are mainly physical, namely skinfolds. Following puberty the major factors that reduce gender differences are skinfolds and the amount of exercise done outside of school time.
J.R. Thomas is with the Dept. of Exercise Science and Physical Education at Arizona State University, Tempe, AZ 85287. J.K. Nelson is with the Div. of Teacher Education at the University of Idaho, Moscow, ID 83843. G. Church is with the Dept. of Experimental Statistics at Louisiana State University, Baton Rouge, LA 70803.