Purpose:

To examine any potential, independent, association between sedentary behaviour and physical fitness among the ALSPAC adolescents at 13 years old

Background:

Cardiorespiratory fitness (CRF) is an important component of overall physical fitness and low CRF was found to increase the risk of mortality, in adults, independent of fat mass (1). Therefore improving physical fitness should perhaps be a priority, and may have a greater impact upon health outcomes than if weight reduction is solely targeted. Engaging in physical activity is of great benefit to CRF, especially vigorous physical activity (2). However, physical activity does not explain all the variance in CRF (2). Therefore, specifically reducing the time spent sedentary may be of importance. Previous studies involving adults and children have shown sedentary behaviour to be independently associated with various health outcomes (3, 4). However, there is a lack of research concerning the independent effects of sedentary behaviour upon CRF, and this information could potentially help ameliorate morbidity and mortality rates seen in later life (1).

Variables

- Dependent Variable:

? Physical Fitness (PWC 170; 13 year olds; clinical)

- Independent Variable:

? Sedentary Behaviour (hours per day, accelerometry; 13 years old; clinical)

- Covariates:

? Age, pubertal status (chronological and biological maturation; 13 years old; child-response questionnaire)

? Birth length, birth weight, gestation, TV viewing (38mo) and sleep patterns (30mo) (intrauterine factors and early life factors; parental/birth records, 30 and 38 month questionnaire)

? Parental height, parental BMI, social class, maternal smoking during pregnancy, maternal education at time of birth (parental and sociodemographic factors; 32 week questionnaire)

? Adolescents total fat mass (body composition measure; 13 years old; DXA)

? MVPA (physical activity, accelerometer; 13 years old; clinical)