Secular changes in pediatric aerobic fitness test performance: the global picture.

INTRODUCTION: Current attitudes towards secular changes in pediatric aerobic fitness are highly polarized, both in the popular and scientific literature. Few studies have actually quantified secular changes in pediatric aerobic fitness, with most making only informal comparisons. The aim of this study therefore, was to quantify the global change in pediatric aerobic fitness test performance.
METHODS: Following an extensive review of the literature, 33 pediatric studies examining secular changes in maximal field running tests of aerobic performance were analyzed. Secular changes were calculated at the country x study x age x sex x test level using least squares linear regression weighted by the square root of sample size. All secular changes were expressed as a percentage of the weighted mean value for all data points in the regression. Negative values indicated performance declines, and positive values improvements.
RESULTS: Secular changes in aerobic performance were calculated for 25,455,527 6- to 19-year-old from 27 countries (representing five geographical regions) between 1958 and 2003. Over the 45-year period, there has been a global decline in aerobic performance of -0.36% per annum. Secular changes have been very consistent across age, sex, and geographical groups. The pattern of change however, was not consistent over time, with improvements from the late 1950s until about 1970, and declines of increasing magnitude every decade thereafter. DISCUSSION/
CONCLUSION: This study provides the most comprehensive picture to date, of the global change in pediatric aerobic performance. It shows that there has been a precipitous decline in pediatric aerobic performance since 1970, a pattern which is not observed in pediatric anaerobic performance. This secular decline may result from a network of social, behavioral, physical, psychosocial and physiological factors.