Fig. 4

Mean Relative Leg Extension Strength to Body Weight (lb/kg) by Income. N = 675 (Boys n = 330, Girls n = 345). The number within each bar indicates the least squares mean value of the group. Each error bar indicates 95% confidence interval for the mean and was estimated after controlling for child’s age. a = significant difference between low and high (FIPR > = 350%) income groups, controlling for child’s age (p = 0.023). c = significant difference between low (FIPR < 130%) and middle (FIPR 130–349%) income groups, controlling for child’s age (p = 0.017)