An evaluation of five indices of physical working capacity in children.

The purposes of this study were 1) to analyze race, sex, and body surface area (BSA) differences in the mean work to exhaustion index, maximal endurance index, rate-pressure product, maximum power, and physical working capacity index (PWC) of 383 healthy children, ages 5-16 yr, by using an alternative method of statistical analysis than has been used in previous studies of this type; and 2) to determine which index best measures relative physical working capacity in children. As a result of a three-way analysis of variance test, strong interaction effects were found among race, sex, and BSA on all but one of the indices. In general, the results indicated that the differences between males and females and between blacks and whites in physical working capacity were not consistent across all BSA groups. This suggests that normal values for these indices should be separated into race, sex, and BSA groupings. Based on correlation coefficients, it was also found that all the indices except PWC were biased by age and height differences. In addition, PWC was the only working capacity index to discriminate properly among underweight, normal, and overweight children. It was concluded that of the five indices tested, PWC was the best index of relative physical working capacity for use with children.