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 .
Association between bone stiffness and nutritional biomarkers combined with weight-bearing exercise, physical activity, and sedentary time in preadolescent children. A case-control study.
Physical activity ( PA ) and micronutrients such as calcium ( Ca ) , vitamin D ( 25OHD ) , and phosphate ( PO ) are important determinants of skeletal development . This case-control study examined the association of these nutritional biomarkers and different PA behaviours , such as habitual PA , weight-bearing exercise ( WBE ) and sedentary time ( SED ) with bone stiffness ( SI ) in 1819 2 - 9-year-old children from the IDEFICS study ( 2007 - 2008 ) .  SI was measured on the calcaneus using quantitative ultrasound .  Serum and urine Ca and PO and serum 25OHD were determined . Children 's sports activities were reported by parents using a st and ardised question naire . A sub sample of 1089 children had accelerometer-based PA data ( counts per minute , cpm ) . Moderate-to-vigorous PA ( MVPA ) and SED were estimated . Children with poor SI ( below the 15th age-/sex-/height-specific percentile ) were defined as cases ( N=603 ) . R and omly selected controls ( N=1216 ) were matched by age , sex , and country . Odds ratios ( OR ) for poor SI were calculated by conditional logistic regression for all biomarkers and PA behaviour variables separately and combined ( expressed as tertiles and dichotomised variables , respectively ) . ORs were adjusted for fat-free mass , dairy product consumption , and daylight duration . We observed increased ORs for no sports ( OR=1.39 , p<0.05 ) , PA levels below 524 cpm ( OR=1.85 , p<0.05 ) and MVPA below 4.2 % a day ( OR=1.69 , p<0.05 ) compared to WBE , high PA levels ( < 688 cpm ) and high MVPA ( 6.7 % ) , respectively . SED was not associated with SI . ORs were moderately elevated for low serum Ca and 25OHD . However , biomarkers were not statistically significantly associated with SI and did not modify the association between PA behaviours and SI . Although nutritional biomarkers appear to play a minor role compared to the osteogenic effect of PA and WBE , it is noteworthy that the highest risk for poor SI was observed for no sports or low MVPA combined with lower serum Ca ( < 2.5 mmol/l ) or lower 25OHD ( < 43.0 nmol/l )
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 .