Gender and ethnic changes in physical work capacity from childhood through adolescence.

This study determined gender and ethnic differences in physical work capacity (PWC170) of 8-16-year-old American youth as they progress from elementary to high school. A multicohort group of 2,540 youth participated 50.4% girls (21.4% African Americans, and 78.6% Caucasians). PWC170 was predicted from cycle ergometer testing six times over a 7-year period. The absolute PWC170 of girls stabilized in early adolescence, while boys increased with each trial. The PWC170 relative to body weight of girls decreased steadily, whereas the boys remained stable. African Americans had greater absolute PWC170 values than Caucasians (p = .0001). The relative PWC170 was lower for African American girls than Caucasian girls (p = .0001), but there were no ethnic differences for boys (p > .05). Although correlations and grouping suggested moderate tracking; girls with high relative PWC170 tended to migrate to lower levels as they aged, where as high-peforming boys maintained their PWC170 as they aged.