***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: Summary Preliminary prospect i ve , longitudinal results suggest that pre-menarcheal exposure to artistic gymnastics is associated with greater radius BMC , aBMD , and projected area throughout growth and into early adulthood , more than 4 years after activity cessation . Any loss of benefit associated with de-training appears to be temporary . Introduction Mechanical loading may enhance bone accrual during growth , but prospect i ve evidence of benefit retention is limited . This prospect i ve , longitudinal cohort study tests whether gymnastics is linked to distal radius advantages during growth and four or more years post-training cessation . Methods Semi-annually , female ex/gymnasts and non-gymnasts underwent height and weight measurements ; question naires assessed calcium intake , physical activity , and maturation . Annual dual energy X-ray absorptiometry scans ( Hologic QDR 4500W ) measured total body fat-free mass , skull areal density ( aBMD ) , and bone mineral content ( BMC ) ; forearm scans measured ultradistal and 1/3 radius area , BMC , and aBMD . Analysis inclusion criteria were : ( 1 ) achievement of gynecological age > 4 years and ( 2 ) for gymnasts , > 2 years of pre-menarcheal training ( > 6 h/week ) , ceasing between 0.5 year pre-menarche and 1 year post-menarche . Hierarchical linear modeling ( HLM v6.0 ) evaluated outcomes for ex/gymnasts versus non-gymnasts ; a slope/intercept discontinuity evaluated de-training effects . Results Data from 14 non-gymnasts and six ex/gymnasts represented outcomes from 4 years pre-menarche to 9 years post-menarche . All adjusted distal radius parameters were higher in ex/gymnasts than non-gymnasts ( p < 0.02 ) . Ultradistal BMC , ultradistal aBMD , and 1/3 aBMD temporarily decreased with gymnastic cessation ( p < 0.04 ) ; ultradistal area , 1/3 area , and 1/3 BMC did not change significantly . Skull outcomes did not differ between groups or change with activity cessation . Conclusion Gymnastic exposure during childhood and early puberty is associated with greater radius bone mass , size , and aBMD . Despite brief de-training losses in density and mass , significant skeletal benefits are manifested throughout growth and at least 4 years beyond activity cessation into early adulthood OBJECTIVE To evaluate the effect of a 3-year after-school physical activity ( PA ) intervention on aerobic fitness and percent body fat ( % BF ) . METHODS In total , 18 schools were r and omized into intervention or control arms . Measurements were made at the beginning and end of the third , fourth and fifth grade s. Fitness was measured with heart rate response to a bench-stepping task.%BF and bone density were measured with dual-energy x-ray absorptiometry . The intervention included 40 min of academic enrichment activities , during which healthy snacks were provided , and 80 min of moderate-to-vigorous PA ( MVPA ) . RESULTS Data analyses were performed on 206 youths who remained in the same schools for the 3-year period , who were measured at all six time points and , for the intervention group , who attended at least 40 % of the sessions in each of the 3 years . The group by time interactions were significant for fitness ( p < 0.01 ) and % BF ( p < 0.05 ) . Children in intervention schools improved in fitness and % BF during the school years and returned to levels similar to those in control schools during the summers . Over the six measurement points , the intervention group increased more than the control group in bone density ( p < 0.01 ) , fat-free soft tissue ( p < 0.01 ) , weight ( p < 0.01 ) , height ( p < 0.01 ) , and body mass index ( p < 0.05 ) . CONCLUSIONS An after-school program focusing on MVPA had a beneficial effect on fitness and body composition . During the summers , the beneficial effect of the previous year 's participation on fitness and % BF was lost . This highlights the importance of year-round programs to promote healthy growth in youths BACKGROUND The aim of this study was to investigate stability of physical activity  from childhood and adolescence to adulthood in multiple age cohorts , and analyze how well adult physical activity can be predicted by various physical activity variables measured in childhood and adolescence . METHODS The data were drawn from the Cardiovascular Risk in Young Finns Study . The study was started in 1980 , when cohorts of r and omly sample d boys and girls aged 3 , 6 , 9 , 12 , 15 , and 18 years ( total of 2309 subjects ) were examined for the first time . The measurements were repeated in 1983 , 1986 , 1989 , 1992 , and 2001 . In 2001 , the subjects ( n = 1563 , 68 % ) were aged 24 , 27 , 30 , 33 , 36 , and 39 years , respectively .  Physical activity  was measured by means of a short self-report question naire that was administered individually in connection with a medical examination . On the basis of a question naire , a physical activity index ( PAI ) was calculated . There were no significant differences in the 1980 PAI between participants and dropouts in 2001 . RESULTS Spearmans rank order correlation coefficients for the 21-year tracking period varied from 0.33 to 0.44 in males , and from 0.14 to 0.26 in females . At shorter time intervals the correlation was higher . On average , the tracking correlation was lower in females than in males . Persistent physical activity , defined as a score in the most active third of the PAI in two or three consecutive measurements , increased the odds that an individual would be active in adulthood . Odds ratios for 3-year continuous activity versus continuous inactivity varied from 4.30 to 7.10 in males and 2.90 to 5.60 in females . The corresponding odds ratios for 6-year persistence were 8.70 to 10.80 and 5.90 to 9.40 . CONCLUSIONS It was concluded that a high level of physical activity at ages 9 to 18 , especially when continuous , significantly predicted a high level of adult physical activity . Although the correlations were low or moderate , we consider it important that school-age physical activity appears to influence adult physical activity , and through it , the public health of the general population Exercise during growth has a positive influence on bone mineral accrual , yet little is known about how bone geometry and strength adapt to loading during growth . Our primary objective was to compare changes in proximal femur bone geometry and strength between 31 prepubertal ( Tanner Stage 1 ) boys who participated in a school-based , high-impact circuit intervention ( 12 min , three times a week ) for 20 months and 33 maturity-matched controls . Our secondary objective was to compare changes in total body ( TB ) , proximal femur ( PF ) , and lumbar spine ( LS ) bone mineral content ( BMC ) and bone area ( BA ) in these groups . We assessed geometric variables and bone strength at the narrow neck ( NN ) , intertrochanteric ( TR ) region , and femoral shaft regions by applying the Hip Structure Analysis program to proximal femur dual energy X-ray absorptiometry scans ( DXA , Hologic QDR 4500 ) . Further , we assessed total body , lumbar spine , and proximal femur BMC and BA by DXA and derived total body lean mass and fat mass from total body scans . Intervention ( 10.2 + /- 0.5 years ) and control boys ( 10.1 + /- 0.5 years ) had similar baseline height ( 140.8 vs. 141.3 cm ) and weight ( 36.9 vs. 35.4 kg ) , and average 20-month physical activity scores ( Physical Activity Question naire for Children , PAQ-C ) and calcium intakes ( 861 vs. 852 mg/day , food frequency question naire ) . Twenty-month height and weight changes were not significantly different between groups ; lean mass changed more ( P < 0.05 ) in intervention boys ( 22.8 % ) than control boys ( 18.6 % ) . At the NN region , intervention boys had greater bone expansion on both the periosteal ( + 2.6 % , P = 0.1 ) and endosteal ( + 2.7 % , P = 0.2 ) surfaces , result ing in significantly greater changes in section modulus ( bone bending strength ) ( + 7.5 % , P = 0.02 , ANCOVA , adjusting for height change , final Tanner Stage , and baseline bone values ) . Changes at the intertrochanteric and femoral shaft regions were not significantly different between groups . Femoral neck ( FN ) BMC changes were significantly greater in intervention boys ( + 4.3 % , P < 0.01 ) ; changes in BA and BMC for other regions were not significantly different between groups . In summary , a school-based , high-impact exercise intervention implemented three times a week for 12 min is an effective strategy for site-specific gains in bone strength at the narrow neck region of the proximal femur The POWER PE study was an 8-mo , r and omized , controlled , school-based exercise intervention design ed to apply known principles of effective bone loading to practical opportunities to improve life-long musculoskeletal outcomes . A total of 99 adolescents ( 46 boys and 53 girls ) with a mean age of 13.8 + /- 0.4 yr ( peri- to postpubertal ) volunteered to participate . Intervention subjects performed 10 min of jumping activity in place of regular physical education ( PE ) warm up . Control subjects performed usual PE warm-up activities .  Bone mass ( DXA and QUS ) was assessed at baseline and follow-up along with anthropometry , maturity , muscle power , and estimates of physical activity and dietary calcium . Geometric properties ( such as femoral neck [ FN ] moment of inertia ) were calculated from DXA measures . Boys in the intervention group experienced improvements in calcaneal broadb and ultrasound attenuation ( BUA ) ( + 5.0 % ) and fat mass ( -10.5 % ) , whereas controls did not ( + 1.4 % and -0.8 % , respectively ) . Girls in the intervention group improved FN BMC ( + 13.9 % ) and lumbar spine ( LS ) BMAD ( + 5.2 % ) more than controls ( + 4.9 % and + 1.5 % , respectively ) . Between-group comparisons of change showed intervention effects only for whole body ( WB ) BMC ( + 10.6 % versus + 6.3 % ) for boys . Boys in the intervention group gained more lean tissue mass , trochanter ( TR ) BMC , LS BMC , and WB BMC and lost more fat mass than girls in the intervention group ( p < 0.05 ) . Ten minutes of jumping activity twice a week for 8 mo during adolescence seems to improve bone accrual in a sex-specific manner . Boys increased WB bone mass and BUA , and reduced fat mass , whereas girls improved bone mass at the hip and spine OBJECTIVE Childhood weight-bearing physical activity is recognized as an important determinant of peak bone mass , and physical activity intervention may represent a feasible strategy for primary prevention of osteoporosis . Previous school-based exercise interventions have all been of < 10 months in duration . We implemented a high-impact , circuit-based , jumping intervention ( 10 minutes , 3 times a week ) over 2 school years and compared changes in bone mineral content ( BMC ) over 20 months ( 2 school years ) in 9.9 + /- 0.6-year-old intervention girls ( N = 32 ) and controls ( 10.3 + /- 0.4 years , N = 43 ) . METHODS We measured BMC for the total body , lumbar spine , proximal femur ( and femoral neck and trochanteric subregions ) , and lean and fat mass by dual-energy radiograph absorptiometry ( Hologic QDR 4500 ) , and height , sitting height , leg length , and weight at baseline and 20 months . We assessed Tanner stage , general physical activity , and calcium intake by question naire . RESULTS Girls were Tanner breast stage 1 to 3 at baseline . There were no significant differences in baseline or 20-month change in body size or composition , average physical activity , or calcium intake between groups . There were substantially greater gains in lumbar spine ( 41.7 % vs 38.0 % ) and femoral neck ( 24.8 % vs 20.2 % ) BMC in intervention than in control girls ( P < .05 , analysis of covariance ; covariates were baseline BMC and height , change in height , physical activity , and final Tanner stage ) . CONCLUSION Three brief sessions of high-impact exercise per week implemented over 2 consecutive years within the elementary school curriculum elicited a substantial bone mineral accrual advantage in pubertal girls Background Vitamin D insufficiency in children may have long-term skeletal consequences as vitamin D affects calcium absorption , bone mineralization and bone mass attainment . Methodology /Principal Findings This school-based study investigated vitamin D status and its association with vitamin D intake and bone health in 195 Finnish children and adolescents ( age range 7–19 years ) . Clinical characteristics , physical activity and dietary vitamin D intake were evaluated . Blood and urine sample s were collected for serum 25-hydroxyvitamin D ( 25-OHD ) and other parameters of calcium home 
    Output:
    
Beneficial effects of school-based , bone-targeted exercise were observed for bone and fat , but not for lean mass .
Considerable study heterogeneity may have obscured effects on lean mass .
The effects observed for bone and fat support the pursuit of brief , jumping-focused interventions to reduce fat as well as enhance musculoskeletal tissue in school age children