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 .
Sitting time and mortality from all causes, cardiovascular disease, and cancer.
PURPOSE Although moderate-to-vigorous physical activity is related to premature mortality , the relationship between sedentary behaviors and mortality has not been fully explored and may represent a different paradigm than that associated with lack of exercise . We prospect ively examined  sitting time  and mortality in a representative sample of 17,013 Canadians 18 - 90 yr of age . METHODS Evaluation of  daily sitting time  ( almost none of the time , one fourth of the time , half of the time , three fourths of the time , almost all of the time ) ,  leisure time physical activity , smoking status , and alcohol consumption  was conducted at baseline . Participants were followed prospect ively for an average of 12.0 yr for the ascertainment of mortality status . RESULTS There were 1832 deaths  ( 759 of cardiovascular disease ( CVD ) and 547 of cancer ) during 204,732 person-yr of follow-up . After adjustment for potential confounders , there was a progressively higher risk of mortality across higher levels of sitting time from all causes ( hazard ratios ( HR ) : 1.00 , 1.00 , 1.11 , 1.36 , 1.54 ; P for trend < 0.0001 ) and CVD ( HR:1.00 , 1.01 , 1.22 , 1.47 , 1.54 ; P for trend < 0.0001 ) but not cancer . Similar results were obtained when stratified by sex , age , smoking status , and body mass index . Age-adjusted all-cause mortality rates per 10,000 person-yr of follow-up were 87 , 86 , 105 , 130 , and 161 ( P for trend < 0.0001 ) in physically inactive participants and 75 , 69 , 76 , 98 , 105 ( P for trend = 0.008 ) in active participants across sitting time categories . CONCLUSIONS These data demonstrate a dose-response association between  sitting time  and mortality from all causes and CVD , independent of leisure time physical activity . In addition to the promotion of moderate-to-vigorous physical activity and a healthy weight , physicians should discourage sitting for extended periods
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 .