Open Access Highly Accessed Research article

Factors associated with low fitness in adolescents – A mixed methods study

Richard Charlton1, Michael B Gravenor1, Anwen Rees2, Gareth Knox3, Rebecca Hill1, Muhammad A Rahman1, Kerina Jones1, Danielle Christian4, Julien S Baker5, Gareth Stratton6 and Sinead Brophy1*

Author Affiliations

1 College of Medicine, Swansea University, Swansea SA2 8PP, UK

2 School of Sport, University of Wales Institute Cardiff, Cardiff CF23 6XD, UK

3 Applied Sport Science University of West of England (Hartpury College), Gloucester, England

4 College of Health and Human Sciences, Swansea University, Swansea SA2 9PP, UK

5 Institute of Clinical Exercise and Health Science, School of Science, University of the West of Scotland, Hamilton, Lanarkshire ML3 OJB, Scotland

6 College of Engineering, Swansea University, Swansea SA2 8PP, UK

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BMC Public Health 2014, 14:764  doi:10.1186/1471-2458-14-764

Published: 29 July 2014



Fitness and physical activity are important for cardiovascular and mental health but activity and fitness levels are declining especially in adolescents and among girls. This study examines clustering of factors associated with low fitness in adolescents in order to best target public health interventions for young people.


1147 children were assessed for fitness, had blood samples, anthropometric measures and all data were linked with routine electronic data to examine educational achievement, deprivation and health service usage. Factors associated with fitness were examined using logistic regression, conditional trees and data mining cluster analysis. Focus groups were conducted with children in a deprived school to examine barriers and facilitators to activity for children in a deprived community.


Unfit adolescents are more likely to be deprived, female, have obesity in the family and not achieve in education. There were 3 main clusters for risk of future heart disease/diabetes (high cholesterol/insulin); children at low risk (not obese, fit, achieving in education), children ‘visibly at risk’ (overweight, unfit, many hospital/GP visits) and ‘invisibly at risk’ (unfit but not overweight, failing in academic achievement). Qualitative findings show barriers to physical activity include cost, poor access to activity, lack of core physical literacy skills and limited family support.


Low fitness in the non-obese child can reveal a hidden group who have high risk factors for heart disease and diabetes but may not be identified as they are normal weight. In deprived communities low fitness is associated with non-achievement in education but in non-deprived communities low fitness is associated with female gender. Interventions need to target deprived families and schools in deprived areas with community wide campaigns.

Eduation and health; Risk factors; Diabetes; Heart disease; Physical activity