The relative decline in MVPA affects both sexes from an early age ; however , it is greater among girls .
Moderate-to-vigorous-intensity  physical activity ( MVPA )  is important for childhood obesity prevention and treatment , yet declines with age .
Timing and magnitude of the decline in MVPA in children and adolescents are unclear but important for informing effective obesity intervention development .
This systematic review aim ed to determine and compare the year-to-year changes in MVPA among children and adolescents .
The effect of dance mat exergaming systems on physical activity and health – related outcomes in secondary schools: results from a natural experiment
Background Exergaming has been proposed as an innovative method for physical activity promotion . However , large effectiveness studies are rare . In January 2011 , dance mat systems  were introduced in secondary schools in two districts in Engl and with the aim of promoting an innovative opportunity for physical activity . The aim of this natural experiment was to examine the effect of introducing the dance mat exergaming systems on physical activity and health-related outcomes in 11–13 year old students using a non-r and omised controlled design and mixed methods . Methods Participants were recruited from five schools in intervention districts ( n = 280 ) and two schools in neighbouring control districts ( n = 217 ) .  Data on physical activity ( accelerometer ) , anthropometrics ( weight , BMI and percentage of body fat ) , aerobic fitness ( 20-m multistage shuttle run test ) , health-related quality of life ( Kidscreen question naire ) , self-efficacy ( children ’s physical activity self-efficacy survey ) , school attendance , focus groups with children and interviews with teachers were collected at baseline and approximately 12 months follow-up . Results There was a negative intervention effect on total physical activity ( -65.4 cpm CI : -12.6 to -4.7 ) , and light and sedentary physical activity when represented as a percentage of wear time ( Light : -2.3 % CI : -4.5 to 0.2 ; Sedentary : 3.3 % CI : 0.7 to 5.9 ) . However , compliance with accelerometers at follow-up was poor . There was a significant positive intervention effect on weight ( -1.7 kg , 95 % CI : -2.9 to -0.4 ) , BMI ( -0.9 kg/m2 , 95 % CI : -1.3 to -0.4 ) and percentage of body fat ( -2.2 % , 95 % CI : -4.2 to -0.2 ) . There was also evidence of improvement in some health-related quality of life parameters : psychological well-being ( 2.5 , 95 % CI : 0.1 to 4.8 ) and autonomy and parent relation ( 4.2 , 95 % CI : 1.4 to 7.0 ) . Conclusions The implementation of a dance mat exergaming scheme was associated with improvement in anthropometric measurements and parameters of health-related quality of life . However , the mechanisms of these benefits are unclear as there was insufficient data from physical activity to draw robust conclusions . Qualitative findings suggest that there was declining support for the initiative over time , meaning that potential benefits may not have been achieved
The relative decline in MVPA affects both sexes from an early age ; however , it is greater among girls .
Moderate-to-vigorous-intensity  physical activity ( MVPA )  is important for childhood obesity prevention and treatment , yet declines with age .
Timing and magnitude of the decline in MVPA in children and adolescents are unclear but important for informing effective obesity intervention development .
This systematic review aim ed to determine and compare the year-to-year changes in MVPA among children and adolescents .