Several studies that used DXA or quantitative ultrasound suggested that objective ly measured SB was negatively associated with lower extremity bone outcomes , such as femoral neck bone mineral density .
The magnitude of this negative association was small and independent of moderate-to-vigorous physical activity .
In contrast to the lower extremities , there was insufficient evidence for an association of lumbar spine bone outcomes with objective ly measured SB .
In high- quality studies that used DXA , no association was observed between objective ly measured SB and total body bone outcomes .
In studies using question naires , none of these relationships were observed .
Sedentary  behaviour ( SB ) is increasing in Western societies and some studies suggest a deleterious effect of SB on bone .
The aim of this systematic review was to examine the association between  SB and bone health in children , adolescents and young adults .
Television, computer, and video viewing; physical activity; and upper limb fracture risk in children: a population-based case control study.
UNLABELLED The effect of physical activity on upper limb fractures was examined in this population -based case control study with 321 age- and gender-matched pairs .  Sports participation increased fracture risk in boys and decreased risk in girls . Television viewing had a deleterious dose response association with wrist and forearm fractures while light physical activity was protective . INTRODUCTION The aim of this population -based case control study was to examine the association between television , computer , and video viewing ; types and levels of physical activity ; and upper limb fractures in children 9 - 16 years of age . MATERIAL S AND METHODS A total of 321 fracture cases and 321 r and omly selected individually matched controls were studied .  Television , computer , and video viewing and types and levels of physical activity were determined by interview-administered question naire . Bone strength was assessed by DXA and metacarpal morphometry . RESULTS In general , sports participation increased total upper limb fracture risk in boys and decreased risk in girls . Gender-specific risk estimates were significantly different for total , contact , noncontact , and high-risk sports participation as well as four individual sports ( soccer , cricket , surfing , and swimming ) . In multivariate analysis , time spent television , computer , and video viewing in both sexes was positively associated with wrist and forearm fracture risk ( OR 1.6/category , 95 % CI : 1.1 - 2.2 ) , whereas days involved in light physical activity participation decreased fracture risk ( OR 0.8/category , 95 % CI : 0.7 - 1.0 ) . Sports participation increased h and ( OR 1.5/sport , 95 % CI : 1.1 - 2.0 ) and upper arm ( OR 29.8/sport , 95 % CI : 1.7 - 535 ) fracture risk in boys only and decreased wrist and forearm fracture risk in girls only ( OR 0.5/sport , 95 % CI : 0.3 - 0.9 ) . Adjustment for bone density and metacarpal morphometry did not alter these associations . CONCLUSION There is gender discordance with regard to sports participation and fracture risk in children , which may reflect different approaches to sport . Importantly , television , computer , and video viewing has a dose-dependent association with wrist and forearm fractures , whereas light physical activity is protective . The mechanism is unclear but may involve bone-independent factors , or less likely , changes in bone quality not detected by DXA or metacarpal morphometry
Several studies that used DXA or quantitative ultrasound suggested that objective ly measured SB was negatively associated with lower extremity bone outcomes , such as femoral neck bone mineral density .
The magnitude of this negative association was small and independent of moderate-to-vigorous physical activity .
In contrast to the lower extremities , there was insufficient evidence for an association of lumbar spine bone outcomes with objective ly measured SB .
In high- quality studies that used DXA , no association was observed between objective ly measured SB and total body bone outcomes .
In studies using question naires , none of these relationships were observed .
Sedentary  behaviour ( SB ) is increasing in Western societies and some studies suggest a deleterious effect of SB on bone .
The aim of this systematic review was to examine the association between  SB and bone health in children , adolescents and young adults .