Pediatric Fitness

Secular Trends and Geographic Variability

Editor(s): Tomkinson G.R. (Adelaide, S.A.) 
Olds T.S. (Adelaide, S.A.) 
Table of Contents
Vol. 50, No. , 2007
Section title: Paper
Tomkinson GR, Olds TS (eds): Pediatric Fitness. Secular Trends and Geographic Variability. Med Sport Sci. Basel, Karger, 2007, vol 50, pp 226-240

Declines in Aerobic Fitness: Are They Only Due to Increasing Fatness?

Olds T.S.a · Ridley K.c · Tomkinson G.R.b
aNutritional Physiology Research Centre and b Centre for Applied Anthropometry, School of Health Sciences, University of South Australia, and c School of Education, Flinders University, Adelaide, Australia


Aims: This study quantifies the cross-sectional and longitudinal relationships between young people’s fatness (BMI, skinfold thickness) and fitness (performance on tests of aerobic fitness). Background: Over the last 20-30 years, young people have become fatter and less fit. It is likely that the decline in fitness is largely due to increases in fatness. There are strong mechanistic connections; within cohorts, variability in fatness accounts for about 20% of variability in running performance; there is a strong correlation between overweight prevalence and relative fitness across specific cohorts from different countries; and secular declines in fitness coincide temporally with increases in BMI. Methods: Australians aged 10-12 years tested in 1985 were matched for age, sex, BMI and triceps skinfold thickness with their counterparts tested in 1997 (n = 279 matched pairs), and 12-15 year-old tested in 1995-1996 were matched with their counterparts tested in 1999-2000 (n = 2,834 matched pairs). Performance differences on running tests in the matched datasets were compared with performance differences in the complete (unmatched) datasets. Results: Performance differences persisted even when young people were matched for fatness. Matching for fatness reduced overall performance differentials by 29-61%. Other factors such as reduced physical activity and subsequent training effect are likely to have contributed to the decline.

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