Relationship between TV watching during childhood and adolescence and fitness in adulthood in the Raine Study cohort

To investigate: (1) whether TV watching habits throughout childhood and adolescence, a proxy of sedentary behaviour, impacted cardiorespiratory fitness (CRF) in adulthood, and (2) whether any potential impact of TV watching in childhood and adolescence on CRF in adulthood was changed by adult physical activity (PA) levels. A longitudinal study with questionnaire data available regarding TV watching collected at ages 5, 8, 10, 14, 17 and 20 yrs, allowed trajectories of TV watching to be developed. At age 28 yrs, participants completed a V̇O₂peak test and the International Physical Activity Questionnaire. General linear models tested for differences in CRF (time to exhaustion TTE and V̇O₂peak mL·kg⁻¹·min⁻¹) between TV watching trajectories. The secondary analysis tested the potential effect current PA levels has on the relationship between TV trajectory and fitness. In total, 449 participants [male n = 255 (56.8%), 28.3 ± 0.5 yrs; female n = 194 (43.2%), 28.2 ± 0.4 yrs] were included in the study. Three distinct trajectories of TV watching were identified: High TV, Increasing TV and Low TV. CRF was lowest in the High TV watching trajectory and increased progressively from High to Increasing TV and Increasing to Low TV (all P <.05). Within each of the TV trajectories, those engaging in high levels of current PA had greater CRF than those engaging in low and moderate PA. TV watching in childhood and adolescence negatively impacts upon adult fitness at the age of 28 years. However, this negative impact of historical TV watching on CRF can largely be attenuated by engaging in higher levels of PA in adulthood. Highlights High levels of TV watching during childhood and adolescence have negative downstream impacts on cardiorespiratory fitness in adulthood. Taking part in high levels of physical activity in adulthood partially reverses the negative impact of historical TV watching on adult fitness. Engaging in low levels of TV watching throughout childhood and adolescence does not protect individuals from the detrimental impact of low current physical activity levels. Our findings support important public health messages with relevance to parents, schools and government; to target low levels of sedentary time throughout the developmental years of life, whilst encouraging the adoption of regular physical activity across the lifespan including young adulthood.