Physical activity measures for a large, nationally representative sample of Australian boys and girls aged 9, 12, and 15 were related to multiple dimensions of physical fitness. Physical activity during a one-week period was only modestly related to physical fitness. However, relations tended to be higher for length of time multiplied by METs (METs - minday1) than for time alone, time multiplied by perceived effort, or METs - min day−1 multiplied by effort, whereas time multiplied by effort did no better than time alone. Relations tended to be nonlinear in that progressively higher levels of activity had less positive associations with physical fitness. The pattern and size of the relations were consistent across scores for boys and girls aged 9 to 15. Self-report measures of typical and recent (within one week) physical activity both contributed to the prediction of physical fitness, indicating that both aspects of physical activity are important.
The authors are with the Faculty of Education at the University of Western Sydney, Macarthur, P.O. Box 555, Campbelltown, NSW 2560, Australia.