The study, published online in the British Journal of Sports Medicine, aimed to identify the timing of changes in physical activity during childhood and adolescence.
According to the researchers, led by Professor John Reilly from the University of Strathclyde, there is ‘a widely held and influential view’ that physical activity begins to decline in adolescence.
The authors used data from the longitudinal Gateshead Millennium Cohort Study, and studied physical activity levels of 545 participants at least at two different ages, when they were seven years old and then, where possible, again at nine years of age, 12 years of age and 15 years of age.
Participants were asked to wear accelerometers, an instrument for measuring the acceleration of a moving or vibrating body, during waking hours for seven days, removing only for bed and water-based activities such as showering, bathing and swimming.
The study collected data of children over a follow-up period of eight years.
The total volume of physical activity declined across the 8-year period from the age of seven.
The report found that there is a marked decline in physical activity during childhood, and the age-related decline does not begin in adolescence.
The physical activity decline from childhood occurs in both boys and girls.
The report found that one group studied (19 per cent of boys) maintained relatively high moderate-to-vigorous intensity physical activity, which remained stable between the ages of seven and 15.
The researchers conclude that future research and policy to promote physical activity should start before adolescence and include both boys and girls.
The study’s sample was socio-economically representative of the north-east of England. The report’s authors said that further research was needed to determine whether or not the findings are generally applicable to other areas.
The findings were consistent with other research, such as data from the Iowa Bone Development Study suggesting that the total volume of physical activity declined either steadily or dramatically from the age of five in more than 70 per cent of participants.
The International Children’s Accelerometry Database (ICAD), a global data-pooling initiative, has recently demonstrated that the total volume of physical activity seems to be in steady decline in both girls and boys from around the age of school entry. ICAD data provides no evidence that a decline in physical exercise begins in adolescence, the study observed.
The study concluded that future efforts in clinical practice to combat the decline of physical activity in the population should begin well before adolescence.
‘The main implication of our findings for future research and public health policy in physical activity and health is the need for a much greater emphasis on childhood rather than adolescence, and on both boys and girls,’ the researchers wrote in the study.
‘We should abandon the concept of ‘high risk groups’ (eg, adolescent girls) for low physical activity—most of the paediatric population is at high risk.
‘Changes in physical activity arise as a result of a complex and currently poorly understood combination of biological and environmental influences.'
- Download Timing of the decline in physical activity in childhood and adolescence: Gateshead Millennium Cohort Study here