***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: A 14-y follow-up of 581 children who took part in a r and omized controlled trial of the effect of a milk supplement on growth of children was conducted to investigate the supplement 's effect on adult bone mineral content ( BMC ) and density ( BMD ) . BMC and BMD of the nondominant forearm were measured by single-photon absorptiometry in 371 subjects ( 64 % ) aged 20 - 23 y , at a proximal site ( shaft of radius and ulna ) and at a distal site near the wrist .  BMC s and BMDs tended to be higher in the intervention group ( NS ) . Cross-sectionally , BMD was positively associated with body weight ( P less than 0.01 ) in both sexes ; inversely associated with alcohol consumption ( P less than 0.05 ) , and positively with manual occupation ( NS ) in men ; positively associated with current intakes of calcium ( P less than 0.05 ) , vitamin D ( P less than 0.01 ) , and sports activity during adolescence ( P less than 0.01 ) , and inversely with parity ( NS ) in women . In multiple linear-regression analysis body weight and sports activity during adolescence were stronger determinants of female BMD than was diet Risk factors that are associated with lower bone mineral density ( BMD ) may not necessarily be associated with increased bone loss among premenopausal and perimenopausal women . We determined risk factors for lower premenopausal and perimenopausal BMD while simultaneously determining risk factors for increased 6-year rate of bone loss  among women aged 24–50 years within a population -based prospect i ve cohort study .  BMD of the lumbar spine and femoral neck , reported as t scores , were measured five times within the 6-year study among 614 women who were between the ages of 24 and 44 in 1992/1993 .  Rates of bone loss were calculated from the repeated BMD measurements . Risk factors for lower BMD over time at the lumbar spine included history of any fracture ( P=0.005 ) . The major risk factor for lower BMD over time at the femoral neck was family history of osteoporosis ( P<0.002 ) . The major protective factor for greater BMD over time at both skeletal sites was additional body weight ( P<0.0001 ) . Other protective factors for greater BMD over time at the femoral neck were modest alcohol consumption ( P=0.0002 ) and high-school sports participation ( P=0.002 ) . Risk factors for greater bone loss at either skeletal site included postmenopausal status ( P<0.0001 at the lumbar spine ; P=0.01 at the femoral neck ) , and the reporting of a reproductive cancer ( P<0.0001 at the lumbar spine ; P=0.0008 at the femoral neck ) . Body weight was protective against bone loss at both skeletal sites ( P<0.0001 ) . Baseline age , calcium intake , smoking , and current physical activity were not associated with BMD or bone loss . The underst and ing of the relative importance of risk factors for both low BMD and bone loss may assist in the identification of women at greater risk for subsequent low postmenopausal BMD OBJECTIVE : To test the feasibility of creating a valid and reliable checklist with the following features : appropriate for assessing both r and omised and non-r and omised studies ; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting , internal validity ( bias and confounding ) and power , but also for external validity . DESIGN : A pilot version was first developed , based on epidemiological principles , review s , and existing checklists for r and omised studies . Face and content validity were assessed by three experienced review ers and reliability was determined using two raters assessing 10 r and omised and 10 non-r and omised studies . Using different raters , the checklist was revised and tested for internal consistency ( Kuder-Richardson 20 ) , test-retest and inter-rater reliability ( Spearman correlation coefficient and sign rank test ; kappa statistics ) , criterion validity , and respondent burden . MAIN RESULTS : The performance of the checklist improved considerably after revision of a pilot version . The Quality Index had high internal consistency ( KR-20 : 0.89 ) as did the subscales apart from external validity ( KR-20 : 0.54 ) . Test-retest ( r 0.88 ) and inter-rater ( r 0.75 ) reliability of the Quality Index were good . Reliability of the subscales varied from good ( bias ) to poor ( external validity ) . The Quality Index correlated highly with an existing , established instrument for assessing r and omised studies ( r 0.90 ) . There was little difference between its performance with non-r and omised and with r and omised studies . Raters took about 20 minutes to assess each paper ( range 10 to 45 minutes ) . CONCLUSIONS : This study has shown that it is feasible to develop a checklist that can be used to assess the method ological quality not only of r and omised controlled trials but also non-r and omised studies . It has also shown that it is possible to produce a checklist that provides a profile of the paper , alerting review ers to its particular method ological strengths and weaknesses . Further work is required to improve the checklist and the training of raters in the assessment of external validity We studied the response of bone at specific skeletal sites to either lower body exercise alone or complemented with upper body exercise  in premenopausal women . Thirty-five exercisers and 24 age-matched controls completed the 12-month study . Exercising women ( N = 35 ) were r and omly assigned to either lower body resistance plus jump exercise ( LOWER ) ( N = 19 ) or to lower and upper body resistance plus jump exercise ( UPPER + LOWER ) ( N = 16 ) . Exercisers trained three times per week completing 100 jumps and 100 repetitions of lower body resistance with or without 100 repetitions of upper body resistance exercise at each session . Intensity for lower body exercise was increased using weighted vests for jump and resistance exercises , respectively . Intensity for upper body exercise was increased using greater levels of tautness in elastic b and s. Bone mineral density ( BMD ) at the total hip , greater trochanter , femoral neck , lumbar spine and whole body were measured by dual energy X-ray absorptiometry ( Hologic QDR-1000/W ) at baseline , 6 and 12 months . Data were analyzed first including all enrolled participants who completed follow-up testing and secondly including only those women whose average attendance was > or = 60 % of prescribed sessions . Group differences in 12-month % change scores for BMD variables were analyzed by univariate ANCOVA adjusted for baseline differences in age . Post hoc tests were performed to determine which groups differed from one another . Initial analysis showed significant differences in greater trochanter BMD between each exercise group and controls , but not between exercise groups ( 2.7%+/-2.5 % and 2.2%+/-2.8 % vs. 0.7%+/-1.7 % , for LOWER and UPPER + LOWER vs. controls , respectively ; p < 0.02 ) and near significant group differences at the spine ( p = 0.06 ) . Excluding exercisers with low compliance , group differences at the greater trochanter remained , while spine BMD in UPPER + LOWER was significantly different from LOWER and controls , who were not significantly different from one another ( 1.4%+/-3.9 % vs. -0.9%+/-1.7 % and -0.6%+/-1.8 % , for UPPER + LOWER vs. LOWER and controls , respectively ; p < 0.05 ) . No significant differences among groups were found for femoral neck , total hip or whole body BMD . Our data support the site-specific response of spine and hip bone density to upper and lower body exercise training , respectively . These data could contribute to a site-specific exercise prescription for bone health Objective : To evaluate the contribution to peak bone mass of exercise , smoking , and calcium intake in adolescents and young adults . Design : Prospect i ve cohort study with end point measurement ( bone mineral density ) after 11 years'20follow up for lifestyle . Setting : Five university hospital clinics . Subjects : 264 ( 153 females , 111 males ) subjects aged 9 to 18 years at the beginning of the follow up20 and 20 to 29 years at the time of measurement of bone mineral density . Main outcome measure : Bone mineral density of lumbar spine and femoral neck by  dual energy x ray absorptiometry ; measures of physical activity and 20smoking and estimates of calcium intake  repeated three times during follow up . Results : In the groups with the lowest and highest20levels of exercise the femoral bone mineral densities ( adjusted for age and weight ) were 0.918 and 0.988 g/cm2 for women ( P=0.015 ) , analysis of covariance ) and 0.943 and 1.042 g/cm2 for men ( P=0.005 ) , respectively ; at the lumbar spine the respective20values were 1.045 and 1.131 ( P=0.005 ) for men . In men the femoral bone mineral densities ( adjusted for age , weight , and exercise ) were 1.022 and 0.923 g/cm2 for the groups with the lowest and highest values of smoking index ( P=0.054 , analysis of covariance ) . In women the adjusted femoral bone mineral density increased by 4.7 % together with increasing calcium intake ( P=0.089 , analysis of covariance ) . In multiple regression analysis on bone mineral density of the femoral neck , weight , exercise , age , and smoking were independent predictors for men ; with weight , exercise , and age for women . These predictors together explained 38 % of the variance in bone mineral density in women and 46 % in men . At the lumbar spine , weight , smoking , and exercise were predictors for men ; and only weight for women . Conclusions : Regular exercise and not smoking is important in achieving maximal peak bone mass in adolescents and young adults PURPOSE The present population study is conducted to examine the extent to which lifetime physical activity and lifestyle parameters contribute to  bone mass . METHODS The design of the project is a 27-yr prospect i ve follow-up study . Subjects are 126 males gathered from the Leuven Longitudinal Study on Lifestyle , Physical Fitness and Health , and aged 13 yr at the onset of the study and 40 at the end of the follow-up .  Physical activity and lifestyle parameters are obtained with question naires . Bone mass is measured by means of dual-energy x-ray absorptiometry ( DXA ) . RESULTS Results from correlation and regression analyses show that the body mass index ( BMI ) is the most important parameter in relation to cortical and trabecular bone mass at every examination period . Longitudinally , static arm strength , running speed , and upper muscular endurance contribute significantly to the prediction of adult bone mass . The parameter " change in motor fitness " between 18 and 13 yr old was used to control for hereditary influences . The score for static arm strength and trunk muscle strength demonstrates a significant correlation with adult total bone mineral content ( BMC ) and lumbar bone mineral density ( BMD ) , respectively . At the age of 40 , the Baecke sports index is almost equally important as BMI in explaining the variance in BMD , and static arm strength is the most important parameter ( after BMI ) for BMC . CONCLUSION Lifetime physical activity , physical fitness , and BMI all contribute to adult bone mass . The clinical relevance of these findings is emphasized by the fact that the observed patterns of physical activity and motor fitness pertain to customary lifestyle and are thus feasible targets Summary We carried out a cross-section study of the sex-specific relationship between bone mineral content and  physical activity  at sites with different loading in pre- and early pubertal girls and boys . There was significant sensitivity of bone mineral content of the hip to physical exercise in boys , but not in girls . Background Since little is known whether there are sex differences in sensitivity of bone to loading , we investigated sex differences in the cross-sectional association between measures of physical activity ( PA ) and bone mass and size in pre- and early pubertal children of both sexes . Methods We measured bone mineral content/density ( BMC /BMD ) and fat-free mass ( FFM ) in 269 6- to 13-year-old children from r and omly selected schools by dual-energy X-ray absorptiometry .  Physical activity ( PA ) was measured by accelerometers and lower extremity strength by a jump- and -reach test . Results Boys ( n = 128 ) had higher hip and total body BMC and BMD , higher FFM , higher muscle strength and were more physically active than girls ( n = 141 ) . Total hip BMC was positively associated with time spent in total and vigorous PA  in boys ( r = 0.20–0.33 , p < 0.01 ) , but not in girls ( r = 0.02–0.04 , p = ns ) , even after adjusting for FFM and strength . While boys and girls in the lowest tertile of vigorous PA ( 22 min/day ) did not differ in hip BMC ( 15.62 vs 15.52 g ) , boys in the highest tertile ( 72 min/day ) had significantly higher values than the corresponding girls ( 16.84 vs 15.71 g , p < 0.05 ) . Conclusions Sex differences in BMC during pre- and early puberty may be related to a different sensitivity of bone to physical loading , irrespective of muscle mass Abstract . The objective of this prospect i ve controlled study was to determine whether the osteogenic response of bone 
    Output:
    
Positive associations between physical activity and bone mass were found more in males than in females ; in weight bearing anatomical sites ( lumbar spine and femoral neck ) than in total body and when physical activity measurements were done from adolescence to adulthood – than when evaluated in only one period .
Physical activity during growth period was associated with greater bone mass in males .
Conclusions Physical activity seems to be important for bone mass in all periods of life , but especially the growth period should be taking into account due to its important direct effect on bone mass and its influence in physical activity practice in later life .
Low participation in peak strain activities may also explain the lower number of associations found in females