A 3-Year Physical Activity Intervention Program Increases the Gain in Bone Mineral and Bone Width in Prepubertal Girls but not Boys: The Prospective Copenhagen School Child Interventions Study (CoSCIS) Extracurricular physical activity participation modifies the association between high TV watching and low bone mass. Intervening to Reduce Sedentary Behaviors and Childhood Obesity among School-Age Youth: A Systematic Review of Randomized Trials A combined dietary-physical activity intervention affects bone strength in obese children and adolescents. Higher levels of objectively measured sedentary behavior is associated with worse cognitive ability: Two-year follow-up study in community-dwelling older adults Impact of a school-based physical activity intervention on fitness and bone in adolescent females. A longitudinal study of the relationship of physical activity to bone mineral accrual from adolescence to young adulthood. Adolescence physical activity is associated with higher tibial pQCT bone values in adulthood after 28-years of follow-up--the Cardiovascular Risk in Young Finns Study. The effect of a 9-week physical activity programme on bone and body composition of children aged 10-11 years: an exploratory trial. Physical activity increases bone mass during growth Bone mineral accrual and gain in skeletal width in pre-pubertal school children is independent of the mode of school transportation – one-year data from the prospective observational pediatric osteoporosis prevention (POP) study The effect of a high-impact jumping intervention on bone mass, bone stiffness and fitness parameters in adolescent athletes Bone Size and Bone Mass in 10-Year-Old Danish Children: Effect of Current Diet
 Association between bone stiffness and nutritional biomarkers combined with weight-bearing exercise, physical activity, and sedentary time in preadolescent children. A case-control study. Prevalence of the Female Athlete Triad in High School Athletes and Sedentary Students Lifestyle factors and the development of bone mass and bone strength in young women. Positive, site-specific associations between bone mineral status, fitness, and time spent at high-impact activities in 16- to 18-year-old boys.
The aim of this study was to evaluate the effect of increasing the amount of time spent in physical education classes on bone mineral accrual and gain in bone size in prepubertal Danish children . A total of 135 boys and 108 girls , aged 6–8 years , were included in a school-based curriculum intervention program where the usual time spent in physical education classes was doubled to four classes ( 180 min ) per week . The control group comprised age-matched children ( 62 boys and 76 girls ) recruited from a separate community who completed the usual Danish school curriculum of physical activity ( 90 min/week ) . Dual-energy X-ray absorptiometry was used to evaluate bone mineral content ( BMC ; g ) , bone mineral density ( g/cm2 ) , and bone width at the calcaneus and distal forearm before and after 3 years of intervention . Anthropometrics and Tanner stages were evaluated on the same occasions . General physical activity was measured with an accelerometer worn for 4 days . In girls , the intervention group had a 12.5 % increase ( P = 0.04 ) in distal forearm BMC and a 13.2 % increase ( P = 0.005 ) in distal forearm scanned area compared with girls in the control group . No differences were found between the intervention and control groups in boys . Increasing the frequency of physical education classes for prepubertal children is associated with a higher accrual of bone mineral and higher gain in bone size after 3 years in girls but not in boys OBJECTIVES To examine whether different sedentary behaviours are associated with the risk of  low bone mineral content in adolescents , and if so , whether extracurricular physical-sporting activity influences this association . MATERIAL S AND METHODS A total of 277 adolescents from Zaragoza ( 168 females and 109 males ) aged 13.0 - 18.5 yr within frame work of the multicentre AVENA study participated in this study . Bone mineral content ( BMC ) , lean mass , and fat mass were measured with DXA . Physical activity and sedentary independent variables : participation in extracurricular physical-sporting activity ( PA ) , h/d of television watching , playing video/computer games during school days and on weekend days and doing homework/ study ing . They all were assessed by question naire . The main outcome was low BMC , as defined by BMC Z-score for age and sex < percentile 10 . Logistic regression was used to test the interaction and association of PA and sedentary variables with low BMC , after controlling for confounders like height , maturational status or lean mass . RESULTS Among the sedentary variables studied , only television watching > or =3 h/d was associated with an increased risk for low BMC in males ( OR , 95 % CI : 7.01 , 1.73 to 28.40 ) , after controlling for sexual maturation . When PA was in the models , television watching was not any longer associated with low BMC , while PA was so ( OR , 95 % CI : 0.23 , 0.09 to 0.55 ) . Involvement in such activity reduced the risk of low bone mass by 76 % ( P<0.01 ) independently of body mass , height and fat mass , but not of the lean mass . CONCLUSION Watching television for 3 or more h/d seems to be associated with an increased risk for  low BMC in male adolescents . However , this association is mediated by participation in PA , suggesting that negative consequences of excessive television watching on adolescent bone health could be counteracted by sport participation . Longitudinal data and r and omized controlled trials will confirm or contrast our findings Objective . To assess the effectiveness of interventions that focus on reducing  sedentary behavior ( SB ) among school-age youth and to identify elements associated with interventions ' potential for translation into practice setting s. Methods . A comprehensive literature search was conducted using 4 data bases for peer- review ed studies published between 1980 and April 2011 . R and omized trials , which lasted at least 12 weeks , aim ed at decreasing  SB among children aged 6 to 19 years were identified . Results . Twelve studies were included ; 3 focused only on SB , 1 focused on  physical activity ( PA )  , 6 were combined SB and PA interventions , and 2 studies targeted SB , PA , and diet .  The majority of the studies were conducted in a school setting , while others were conducted in such setting s as clinics , community centers , and libraries . Conclusions . Overall , interventions that focused on decreasing SB were associated with reduction in time spent on SB and /or improvements in anthropometric measurements related to childhood obesity . Several of the studies did consider elements related to the intervention 's potential for translation into practice setting Obesity has become the most common pediatric chronic disease in the modern era . Recent data suggests that unlike obese adults , obese children and adolescents may have decreased bone strength . It was the objective to prospect ively examine the short term effects of a 3 month combined dietary-physical activity intervention on anthropometric measures , body composition , fitness and bone strength in obese children . Twelve obese subjects completed the 3 m intervention  and were compared to 12 obese age and gender matched controls .  Bone strength was measured using quantitative ultrasound measurements of bone speed of sound ( SOS ) . There were significant differences in changes of body weight ( 0.01 + /- 0.7 vs. 2.3 + /- 0.6 kg , p = 0.033 ) , BMI percentiles ( - 2.8 + /- 1.1 vs. - 0.2 + /- 0.2 % , p = 0.037 ) , body fat percent ( by skinfolds , - 1.5 + /- 0.8 vs. 0.7 + /- 0.5 % , p = 0.035 ) , and endurance time ( 170 + /- 42 vs. 50 + /- 27 s , p = 0.045 ) in the intervention vs. control subjects , respectively . In addition , we found a significant difference in the change of bone SOS between the intervention and control group subjects ( 21.5 + /- 21.6 vs. - 87.0 + /- 37 m/s , p = 0.023 ) . During the critical period of bone development of childhood and adolescence , a combined dietary-physical activity intervention leads to increased bone strength in obese children . These results highlight the importance of multi-disciplinary programs for the treatment of childhood obesity and its complications Background : A number of cross‐sectional studies have suggested that higher levels of  sedentary behavior ( SB ) are associated with worse cognitive abilities  in older age . There is a paucity of longitudinal studies investigating this relationship utilizing objective ly assessed SB . This study investigated the relationship between objective ly assessed SB and future cognitive abilities in a cohort of older adults . Methods : A longitudinal study over 22.12 ± 1.46 months including 285 community‐dwelling older adults across 14 regions in Taiwan was undertaken . Cognitive ability was ascertained using a Chinese version of the Ascertain Dementia 8‐item Question naire ( AD8 ) and SB captured by 7 days accelerometer data . Multivariable negative binomial regression models adjusted for confounders were undertaken . Results : 274 community‐dwelling older adults finished the study ( age = 74.6 ± 6.2 , % female = 54.4 % ) . At baseline , 20.1 % ( n = 55 ) , 48.5 % ( n = 133 ) and 31.4 % ( n = 86 ) of the sample engaged in high ( 11 + h ) , medium ( 7–10.99 h ) and low ( < 7 h ) of SB respectively . In the fully adjusted model , higher levels of SB were associated with an increased risk of worse cognitive ability at follow up ( adjusted rate ratio (ARR)1.09 ( 95%CI:1.00–1.19 ) ) , with the strongest relationship evident in those engaging in over 11 h of SB ( ARR 2.27 ( 95%CI:1.24–4.16 ) ) . The relationship remained evident after adjusting for depressive symptoms and physical activity . Conclusion : Our data suggests that objective ly assessed SB , particularly when over 11 h a day , is independently associated with worse cognitive ability over a two year period . Our data adds to the pressing reasons to reduced SB in older age . HighlightsFirst prospect i ve study to investigate objective  ly sedentary behavior ( SB ) and cognition in older adults . Higher levels of objective SB were independently associated with worse cognitive ability over two years . This relationship was most pronounced in older people spending over 11 h a day being sedentary BACKGROUND Many female adolescents participate in insufficient physical activity to maintain cardiovascular fitness and promote optimal bone growth . This study evaluates the impact of a school-based intervention on fitness , activity , and bone among adolescent females . METHODS Subjects were assigned to an  intervention ( n = 63 ) or comparison ( n = 59 ) group , and underwent assessment s of  cardiovascular fitness ( VO2peak )  , physical activity , body composition , bone mineral density ( BMD ) , bone mineral content ( BMC ) , and serum markers of bone turnover  at baseline and at the end of each of two school semesters . RESULTS The intervention increased physical activity , VO2peak , and BMC for the thoracic spine ( P values < 0.05 ) . Bone turnover markers were not affected . In longitudinal analyses of the combined groups , improvements in cardiovascular fitness predicted increased bone formation ( P < 0.01 ) and bone resorption ( P < 0.05 ) . CONCLUSION A school-based intervention for adolescent females effectively increased physical activity , cardiovascular fitness , and thoracic spine BMC Physical activity in adolescence is beneficial for increasing bone mineral accrual ; however , it 's unclear whether these benefits persist into adulthood . This prospect i ve study investigated whether  physically active adolescents maintained their higher bone mineral content ( BMC ) into the third decade of life when compared to their less active peers . Data were from 154 subjects ( 82 females and 72 males ) who participated in the University of Saskatchewan 's Pediatric Bone Mineral Accrual Study ( 1991 - 1997 ) , entry age 8 to 15 years . Participants returned for follow-up as young adults ( 2002 - 2006 ) , follow-up age 23 to 30 years . Dual energy X-ray absorptiometry was used to measure BMC of total body ( TB ) , lumbar spine ( LS ) , total hip ( TH ) and femoral neck ( FN ) annually from 1991 to 1997 and from 2002 to 2006 . Peak height velocity ( PHV ) was determined for each child as a measure of maturity . Age and gender-specific activity Z-scores were calculated for each participant based on the mean physical activity scores obtained from bi-annual question naire data during childhood and adolescence . Subjects were ranked into three adolescent activity groups : active , average and inactive ( top , middle two , and bottom quartiles , respectively ) . Analysis of covariance ( ANCOVA ) was used to compare adjusted TB , LS , TH and FN BMC across the three adolescent activity groups at 1 year post PHV and in young adulthood . When compared to the inactive group , active males had 8 % greater adjusted BMC at the TB , 13 % at the LS and 11 % at the TH ( p<0.05 ) in adolescence . Active females also had 8 % and 15 % more adjusted BMC ( p<0.05 ) at the TB and LS , respectively , during adolescence . In young adulthood the male and female adolescent active groups were still significantly more active than their peers ( p>0.05 ) . It was found that active adolescent males had 8 - 10 % more adjusted BMC at the TB , TH and FN ( p<0.05 ) in young adulthood and that active adolescent females had 9 % and 10 % more adjusted BMC at the TH and FN . These results suggest that the skeletal benefits of physically activity in adolescents are maintained into young adulthood High peak bone mass and strong bone phenotype are known to be partly explained by physical activity during growth but there are few prospect i ve studies on this topic . In this 28-year follow-up of Cardiovascular Risk in Young Finns Study cohort , we assessed whether habitual childhood and adolescence physical activity or inactivity at the age of 3 - 18 years were associated with adult phenotype of weight-bearing tibia and the risk of low-energy fractures . Baseline physical activity  and data on clinical , nutritional and lifestyle factors were assessed separately for females and males aged 3 - 6-years ( N=395 - 421 ) and 9 - 18-years ( N=923 - 965 ) . At the age of 31 - 46-years , the prevalence of low-energy fractures was assessed with a question naire and several tibial traits were measured with pQCT ( bone mineral content ( BMC ; mg ) , total and cortical cross-sectional areas ( mm(2 ) ) , trabecular ( for the distal site only ) and cortical ( for the shaft only ) bone densities ( mg/cm(3 ) ) , stress-strain index ( SSI ; mm(3 ) , for the shaft only ) , bone strength index ( BSI ; mg(2)/cm(4 ) , for the distal site only ) and the cortical strength index ( CSI , for the shaft only ) ) . For the statistical analysis , each bone trait was categorized as below the cohort median or the median and above and the adjusted odds ratios ( OR ) were determined . In females , frequent physical activity at the age of 9 - 18-years was associated with higher adulthood values of BSI , total and cortical areas , BMC , CSI and SSI at the tibia independently of many health and lifestyle factors ( ORs 0.33 - 0.53 , P≤0.05 ; P-values for trend 0.002 - 0.05 ) . Cortical density at the tibial shaft showed the opposite trend ( P-value for trend 0.03 ) . Similarly in males , frequent physical activity was associated with higher values of adult total and cortical areas and CSI at the tibia ( ORs 0.48 - 0.53 , P≤0.05 ; P-values for trend 0.01 - 0.02 ) . However , there was no evidence that childhood or adolescence physical activity was associated with lower risk of low energy fractures during the follow-up . In conclusion , frequent habitual physical activity in adolescence seems to confer benefits on tibial bone size and geometry in adulthood A high-impact exercise and a lifestyle intervention were implemented over a 9-week period ; changes in bone and body composition were compared to controls . Sixty-one children volunteered from three r and omly selected schools . Each school was r and omly assigned to either a structured exercise ( STEX ) intervention , a lifestyle intervention ( PASS ) or control ( CONT ) .  Bone mineral content ( BMC ) and density ( BMD ) of total body , femoral neck and lumbar spine were measured as well as fat and lean mass at baseline and post-intervention by dual-energy X-ray absorptiometry . The STEX intervention result ed in an additional mean increase in total body BMC of 63.3 g ( p = 0.019 ) and an additional increase of 0.011 g . cm ( -2 ) ( p = 0.018 ) for BMD over increases observed by controls . Bone mineral increases observed for the PASS intervention were not significant compared to the control group ( p > 0.05 ) . Neither intervention produced significant increases in bone mineral at femoral neck or lumbar spine sites ( p > 0.05 ) compared with the controls . No significant changes were found in fat mass index ( p > 0.05 ) , lean mass index ( p > 0.05 ) or percent body fat ( p = 0.09 ) in any groups . Structured impact exercise promoted significant and clinical ly relevant increases in bone measures , without significant changes to body composition . A larger , definitive r and omised trial is needed to confirm the present results Background The incidence of fragility fractures has increased during the last half of the 1990′s . One important determinant of fractures is the bone mineral content ( BMC ) or bone mineral density ( BMD ) , the amount of mineralised bone . If we could increase peak bone mass ( the highest value of BMC reached during life ) and /or decrease the age-related bone loss , we could possibly improve the skeletal resistance to fracture . Objective This review evaluates the importance of exercise as a strategy to improve peak bone mass , including some aspects of nutrition . Design Publications within the field were search ed through Medline ( PubMed ) using the search words : exercise ,  physical activity  , bone mass , bone mineral content , bone mineral density , BMC , BMD , skeletal structure and nutrition . We included studies dealing with  exercise during growth and young adolescence . We preferably based our inferences on r and omised controlled trials ( RCT ) , which provide the highest level of evidence . Results Exercise during growth increases peak bone mass .  Moderate intensity exercise intervention programs are beneficial for the skeletal development during growth . Adequate nutrition must accompany the exercise to achieve the most beneficial skeletal effects by exercise . Conclusion Exercise during growth seems to enhance the building of a stronger skeleton through a higher peak bone mass and a larger bone size Background Walking and cycling to school could be an important regular source of physical activity in growing children . The aim of this 12 months prospect i ve observational study was thus to evaluate the effect of self-transportation to school on bone mineral accrual and gain in bone width in pre-pubertal children , both traits independently contributing to bone strength . Methods Ninety-seven girls and 133 boys aged 7–9 years were recruited as a part of the Malmö Pediatric Osteoporosis Prevention ( POP ) Study in order to evaluate the influence of self-selected school transportation for the accrual of bone mineral and bone width .  Children who walked or cycled to school were compared with  children who went by bus or car . Bone mineral content ( BMC ) was measured by dual energy X-ray absorptiometry ( DXA ) in the lumbar spine ( L2–L4 ) , third lumbar vertebra ( L3 ) and hip , and bone width was calculated at L3 and femoral neck ( FN ) . Changes during the first 12 months were compared between the groups . Subjective duration of physical activity was estimated by a question naire and objective level of everyday physical activity at follow-up by accelerometers worn for four consecutive days . All children remained in Tanner stage 1 throughout the study . Comparisons were made by independent student 's t-tests between means , ANCOVA and Fisher 's exact tests . Results There were no differences in baseline or annual changes in BMC or bone width when the transportation groups were compared . No differences were detected in objective ly measured daily level of physical activity by accelerometer . All children reached above 60 minutes of moderate to intense daily physical activity per day , the international recommended level of daily physical activity according to the United Kingdom Expert Consensus Group . Conclusion The everyday physical activity in these pre-pubertal children seems to be so high that the school transportation contributes little to their total level of physical activity . As a result , the choice of school transportation seems not to influence the accrual of bone mineral or gain in bone size during a 12-month follow-up period Summary This study demonstrates that a 9-month jumping intervention can improve bone mass gains and physical fitness performance in adolescent males participating in non-osteogenic sports , such as swimming and cycling . Purpose To examine the effect of a jumping intervention on bone mass , bone stiffness and fitness parameters in adolescents involved in different sports . Methods Ninety-three adolescent male swimmers ( SWI ) , footballers ( FOO ) and cyclists ( CYC ) were r and omised to intervention ( INT ) and sport ( INT-SWI = 19 , INT-FOO = 15 , INT-CYC = 14 ) or sport only ( CON-SWI = 18 , CON-FOO = 15 , CON-CYC = 12 ) groups . The 9-month jumping intervention consisted of 3 levels ( 12 weeks each ) of 20 repetitions per set of counter movement jumps ( CMJ ) using adjustable weight vests ( level 1 = 20 CMJ jumps/set , 0 kg , 3 sets/day , 3 times/week ; level 2 = 20 CMJ jumps/set , 2 kg , 4 sets/day , 3 times/week ; level 3 = 20 CMJ jumps/set , 5 kg , 4 sets/day , 4 times/week ) . Total body bone mineral content ( BMC ) at total body less head ( TBLH ) was measured using dual-energy X-ray absorptiometry and bone stiffness using quantitative ultrasound . Fitness was assessed using the 20-m shuttle run ( 20mSRT ) , CMJ and st and ing long jump ( SLJ ) tests . Results INT-SWI had significantly higher increase in BMC legs and bone stiffness compared to CON-SWI ( 4.2–12.7 % ) . INT-CYC had significantly higher increase in BMC at TBLH and legs and bone stiffness compared to CON-CYC ( 5.0–12.3 % ) . There were no significant differences between INT-FOO and CON-FOO in any bone outcomes ( 0.9–3.9 % ) . The increase in CMJ performance was significantly higher in INT-SWI ( 3.1 cm ) and INT-CYC ( 3.2 cm ) compared to CON-SWI and CON-CYC groups , respectively . Conclusions A 9-month jumping intervention can improve bone mass , bone stiffness and muscular fitness in adolescent males participating in non-osteogenic sports , such as swimming and cycling . Clinical Trial Registration IS RCT N17982776 Abstract : Lifestyle factors , such as diet , are believed to be involved in modifying bone health , although the results remain controversial , particularly in children and adolescents . The objective of the study was to identify associations between dietary factors and whole body bone measurements in 10-year-old children . The study was a cross-sectional analysis of a r and om sample of 105 healthy Danish children , aged 10 years ( 9.97 ± 0.09 ) . Whole body bone mineral content ( BMC ) and bone area ( BA ) were determined by dual-energy X-ray absorptiometry . The influence of diet ( 7 day food records ) on BMC and BA were examined in bi- and multivariate analyses . The mean intakes of calcium , protein , phosphorus and sodium were 1226 mg , 78 g , 1523 mg and 3.3 g , respectively . In bivariate analyses , BMC and BA were strongly positively correlated with height ( p<0.001 ) and weight ( p<0.001 ) , and with intakes of energy ( p<0.005 ) and several nutrients . BMC was adjusted for size by including BA , height and weight in the multiple linear regression , and BA was adjusted for size by including height and weight in the multiple linear regression . In multivariate analyses , size-adjusted BMC was positively associated with calcium intake ( p = 0.02 ) . Size-adjusted BA was positively associated with dietary protein ( p = 0.003 ) , and negatively associated with intakes of sodium ( p = 0.048 ) and phosphorus ( p = 0.01 ) . In conclusion , calcium intake was positively associated with bone mineralization . There was a positive association between protein and BA , while for phosphorus and sodium the association was negative . The findings suggest that in addition to calcium , the intake of other nutrients influences bone development in prepubertal children 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 ) Objective : To determine the prevalence of the female athlete triad ( low energy availability , menstrual dysfunction , and low bone mineral density ) in high school varsity athletes in a variety of sports compared with sedentary students/control subjects . Design : Prospect i ve study . Setting : Academic medical center in the Midwest . Participants : Eighty varsity athletes and 80 sedentary students/control subjects volunteered for this study . Intervention : Subjects completed question naires , had their blood drawn , and underwent bone mineral density testing . Main Outcome Measures : Each participant completed screening question naires assessing eating behavior , menstrual status , and physical activity . Each subject completed a 3-day  food diary . Serum hormonal , thyroid-stimulating hormone , and prolactin levels were determined . Bone mineral density and body composition were measured by dual-energy x-ray absorptiometry . Results : Low energy availability was present in similar numbers of athletes ( 36 % ) and sedentary/control subjects ( 39 % ; P = 0.74 ) . Athletes had more menstrual abnormalities ( 54 % ) compared with sedentary students/control subjects ( 21 % ) ( P < 0.001 ) . Dual-energy x-ray absorptiometry revealed that 16 % of the athletes and 30 % of the sedentary/control subjects had low bone mineral density ( P = 0.03 ) . Risk factors for reduced bone mineral density include sedentary control student , low body mass index , and increased caffeine consumption . Conclusions : A substantial number of high school athletes ( 78 % ) and a surprising number of sedentary students ( 65 % ) have 1 or more components of the triad . Given the high prevalence of triad characteristics in both groups , education in the formative elementary school years has the potential to prevent several of the components in both groups , therefore improving health and averting long-term complications OBJECTIVE To evaluate the contributions of  adolescent calcium intake , oral contraceptive use , and exercise on bone mass and bone strength . Study design Eighty white women participated in 10 years of the Penn State Young Women 's Health Study , a longitudinal study of community participants . We measured bone mineral mass ( g ) , density ( BMD , g/cm(2 ) ) , and body composition from dual energy x-ray absorptiometry and estimated proximal femur section modulus ( bone bending strength ) . Calcium intake was determined from 45 days of prospect i ve food records at regular intervals between the ages of 12 and 22 years . Exercise history and oral contraceptive use were assessed by question naire . RESULTS Daily calcium intakes between the ages of 12 and 22 years ranged from 500 to 1900 mg/d and were not significantly associated with bone gain or bone strength .  Oral contraceptive use during adolescence was not correlated with bone or body composition measurements . Femoral neck BMD did not change from 17 to 22 years of age , but section modulus increased 3 % ( P < .05 ) . Only exercise during adolescence was significantly associated with increased BMD and bone bending strength . CONCLUSIONS  Adolescent lifestyle patterns can influence  young adult bone strength . Our data suggest that exercise is the predominant lifestyle determinant of bone strength for this cohort The incidence of hip and forearm fracture in elderly men in the United Kingdom is a public health issue , but there is limited knowledge on lifestyle factors affecting male bone health . The aim of this cross-sectional study was to evaluate the relationships between whole body and regional bone mineral status and self-reported participation time in no- , low- , moderate- , and high-impact activities and fitness measurements in 16- to 18-year-old boys . One hundred twenty-eight boys underwent absorptiometry ( DXA ) measurements ( Hologic QDR 1000W ) of  bone mineral content ( BMC ) , bone area ( BA ) , and bone mineral density ( BMD ) at the whole body , hip , spine , and forearm . They also completed the EPIC ( European Prospect i ve Investigation of Cancer ) physical activity question naire , which allowed categorization of activities according to impact and aerobic intensity . Fitness and strength were assessed in each subject using estimated VO2 max , grip strength , and back strength . Significant positive relationships were found between BMC , BA , and BMD and the fitness and strength measurements and participation time in high-impact sports at most skeletal sites . The relationships were further examined after adjustment of BMC for height , weight , and bone area , thereby minimizing the influence of body and bone size on these relationships . VO2 max was a significant positive determinant of size-adjusted BMC at the whole body , the ultradistal and one-third radius , and all the hip sites , except the trochanter . Size-adjusted BMC at the forearm sites and trochanter was significantly positively associated with grip strength . Size-adjusted BMC at the whole body and all the hip sites was significantly positively associated with time spent at high-impact activities . Differences in size-adjusted BMC across thirds of time spent at high-impact activities were also examined . Boys in the highest third of high-impact activity had significantly greater size-adjusted whole body BMC and total hip BMC compared to subjects in the lowest third [ + 3.4 (1.2)% for whole body and + 8.5 (2.2)% for hip , both P = 0.001 ] . Boys in the highest third of high-impact activity spent most activity time jogging , playing tennis , football and rugby , basketball , and exercising with weights . Back strength and lean mass were significantly greater in subjects in the highest third compared to those in the middle ( P = 0.02 ) and lowest third ( P = 0.03 ) . No significant differences were found between subjects in each third of high-impact activity for potential confounders including TV viewing , calcium intake , body fat , and height . These findings indicate that participation of male adolescents in a range of high-impact activities for 1 h or more a day is associated with greater bone size and mineral content , especially at the hip
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 .