Maturity negates the gender-related difference in physical activity among youth. Is this equally justified whatever the accelerometer cut-off point used?

Objectives: To examine the consistency in findings about the influence of maturity on the gender-difference in moderate-to-vigorous physical activity (MVPA) of children using different cut-off points for MVPA. Design: Cross-sectional observation study. Methods: The sample involved 253 children (139 boys) of 9.9 +/- 0.9 years. Their physical activity was evaluated using an Actigraph accelerometer. The biological age of children was determined with their estimated age at the peak height velocity, and maturity categories were gender-specific defined. Results: Boys spent more time in MVPA than girls (P<0.0001), and no maturity-related differences were obtained on the whole sample. It was only among boys that differences were found between maturity groups with cut-off points of 3000 cpm (P=0.034), 3200 cpm (P=0.024), and 3600 cpm (P=0.011). At a given maturity level, boys spent significantly more time in MVPA than girls, except with the cut-off point of 1000 cpm (P=0.07). There were higher proportions of sufficiently active boys, but significances were reached only with cut-off points above 3000 cpm. There were no maturity-related differences in the proportion of sufficiently active children as MVPA was computed using cut-off points of 1000 cpm, 2000 cpm or 3000 cpm. Conclusions: The role of maturity in the gender-difference in MVPA seems unclear as one another cut-off point is used among children. Even if a relatively greater consistency was found with the three cut-off points above 3000 cpm, data comparison may require a conversion system until a consensus is reached about the exact value to be used among children. (c) 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.