***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: Treatment with teriparatide ( rDNA origin ) injection [ teriparatide , recombinant human parathyroid hormone ( 1 - 34 ) [ rhPTH(1 - 34 ) ] ] reduces the risk of vertebral and nonvertebral fragility fractures and increases cancellous bone mineral density in postmenopausal women with osteoporosis , but its effects on cortical bone are less well established . This cross-sectional study assessed parameters of cortical bone quality by peripheral quantitative computed tomography ( pQCT ) in the nondominant distal radius of 101 postmenopausal women with osteoporosis who were r and omly allocated to once-daily , self-administered subcutaneous injections of placebo  ( n = 35 ) or teriparatide 20 microg ( n = 38 ) or 40 microg ( n = 28 ) . We obtained measurements of moments of inertia , bone circumferences , bone mineral content , and bone area after a median of 18 months of treatment . The results were adjusted for age , height , and weight . Compared with placebo , patients treated with teriparatide 40 microg had significantly higher total bone mineral content , total and cortical bone areas , periosteal and endocortical circumferences , and axial and polar cross-sectional moments of inertia . Total bone mineral content , total and cortical bone areas , periosteal circumference , and polar cross-sectional moment of inertia were also significantly higher in the patients treated with teriparatide 20 microg compared with placebo . There were no differences in total bone mineral density , cortical thickness , cortical bone mineral density , or cortical bone mineral content among groups . In summary , once-daily administration of teriparatide induced beneficial changes in the structural architecture of the distal radial diaphysis consistent with increased mechanical strength without adverse effects on total bone mineral density or cortical bone mineral content During adolescence , skeletal integrity of girls is largely dependent on menstrual function and impact exercise , yet currently there is limited research regarding the interaction between menstrual status and type of mechanical loading associated with various high school sports . Our purpose was to examine associations of menstrual status , type of mechanical loading , and bone mineral density ( BMD ) in female high school athletes participating in high/odd impact or repetitive/non-impact sport . Participants were 161 female high school athletes ( 15.7+/-1.3 years ; 165.3+/-6.9 cm ; 59.4+/-8.7 kg ) representing high/odd impact ( n=93 , including soccer , softball , volleyball , tennis , lacrosse , and track sprinters and jumpers ) , or repetitive/non-impact sports ( n=68 , including swimmers , cross-country and track distance runners who participated in events > or=800 m ) .  Areal BMD was measured by DXA at the spine ( L1-L4 ) , proximal femur , and total body . Menstrual status was determined by self-report . Athletes with primary , secondary or oligomenorrhea were combined into a single group ( oligo/amenorrheic ) and compared to eumenorrheic athletes . Analysis of covariance ( ANCOVA ) with Bonferroni post hoc comparisons adjusted for age , BMI , and gynecological age were used to compare BMD of athletes in combined mechanical loading and menstrual status groups . We found significantly greater total hip ( p=0.04 ) and trochanter ( p=0.02 ) BMD ( g cm(-2 ) ) among eumenorrheic high/odd impact compared to eumenorrheic repetitive/non-impact athletes , and greater spine ( p=0.01 ) and trochanter ( p=0.04 ) BMD among high/odd impact eumenorrheic athletes compared to repetitive/non-impact oligo/amenorrheic athletes . Chi-squared analysis of BMD Z-scores adjusted for gynecological age showed a significantly greater percentage of repetitive/non-impact athletes ( 33.9 % ) compared to high/odd impact athletes ( 11.8 % ) with low spine BMD for their age ( BMD Z-score < or=-1 SD ) ( p=0.001 ) , indicating that a high percentage of female high school athletes participating in repetitive loading sports , and especially those with oligo/amenorrhea , may not be accruing bone at the expected rate . Female adolescent athletes should be evaluated periodically and advised of the possible negative effects of oligo/amenorrhea on bone health PURPOSE The aim of this study was to investigate and to compare the effect of a 12-wk period of whole-body vibration training and resistance training on human knee-extensor strength . METHODS Sixty-seven untrained females ( 21.4 + /- 1.8 yr ) participated in the study . The whole-body vibration group ( WBV , N = 18 ) and the placebo group ( PL , N = 19 ) performed static and dynamic knee-extensor exercises on a vibration platform . The acceleration of the vibration platform was between 2.28 g and 5.09 g , whereas only 0.4 g for the PL condition . Vibration ( 35 - 40 Hz ) result ed in increased EMG activity , but the EMG signal remained unchanged in the PL condition . The resistance-training group ( RES , N = 18 ) trained knee extensors by dynamic leg-press and leg-extension exercises ( 10 - 20 RM ) . All training groups exercised 3x wk-1 . The control group ( CO , N = 12 ) did not participate in any training . Pre- and postisometric , dynamic , and ballistic knee-extensor strength were measured by means of a motor-driven dynamometer . Explosive strength was determined by means of a counter-movement jump . RESULTS Isometric and dynamic knee-extensor strength increased significantly ( P < 0.001 ) in both the WBV group ( 16.6 + /- 10.8 % ; 9.0 + /- 3.2 % ) and the RES group ( 14.4 + /- 5.3 % ; 7.0 + /- 6.2 % ) , respectively , whereas the PL and CO group showed no significant ( P > 0.05 ) increase . Counter-movement jump height enhanced significantly ( P < 0.001 ) in the WBV group ( 7.6 + /- 4.3 % ) only . There was no effect of any of the interventions on maximal speed of movement , as measured by means of ballistic tests . CONCLUSIONS WBV , and the reflexive muscle contraction it provokes , has the potential to induce strength gain in knee extensors of previously untrained females to the same extent as resistance training at moderate intensity . It was clearly shown that strength increases after WBV training are not attributable to a placebo effect Observational longitudinal research is particularly useful for assessing etiology and prognosis and for providing evidence for clinical decision making . However , there are no structured reporting requirements for studies of this design to assist authors , editors , and readers . The authors developed and tested a checklist of criteria related to threats to the internal and external validity of observational longitudinal studies . The checklist criteria concerned recruitment , data collection , biases , and data analysis and descriptive issues relevant to study rationale , study population , and generalizability . Two raters independently assessed 49 r and omly selected articles describing stroke research published from 1999 to 2003 in six journals : American Journal of Epidemiology , Journal of Epidemiology and Community Health , Stroke , Annals of Neurology , Archives of Physical Medicine and Rehabilitation , and American Journal of Physical Medicine and Rehabilitation . On average , 17 of the 33 checklist criteria were reported . Criteria describing the study design were better reported than those related to internal validity . No relation was found between study type ( etiologic or prognostic ) or word count and quality of reporting . A flow diagram for summarizing participant flow through a study was developed . Editors and authors should consider using a checklist and flow diagram when reporting on observational longitudinal research 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 High calcium intake combined with physical activity during childhood have been shown to improve bone mass accrual and bone mineral density . Our aim was to study the combined effect of calcium and exercise on  bone gain in children . Two milk-powder products containing either 800 mg of calcium phosphate ( calcium ) or not ( placebo ) were r and omly allocated to 113 healthy premenarchal girls on a daily basis for 1 year . The group was composed of 63 exercise ( 7.2 + /- 4 hours of exercise/week ) and 50 sedentary ( 1.2 + /- 0.8 hours of exercise/week ) children . The final experiment had 4 groups : exercise/calcium ( n = 12 ) , exercise/placebo ( n = 42 ) , sedentary/calcium ( n = 10 ) , and sedentary/placebo ( n = 21 ) . Bone mineral density ( BMD ) at 6 skeletal sites and body composition were determined by DXA . Bone age was calculated and the daily spontaneous calcium intake was assessed by a frequency question naire . All the tests were performed at baseline and 1 year by the same observer . BMD gains were significantly greater in the exercise/calcium group than in other groups at the total body ( increase of 6.3 % , p < 0.05 ) , lumbar spine ( 11 % , p < 0.05 ) , femoral neck ( 8.2 % , p < 0.02 ) , and Ward 's triangle ( 9.3 % , p < 0.01 ) . There was no difference between the other groups . These data suggest that calcium supplementation increases the effect of physical exercise on bone mineral acquisition in the period preceding puberty , and that calcium supplementation without physical activity does not improve the BMD acquisition during this period . Physical exercise that stimulates bone accretion needs a high calcium intake to be completely effective PURPOSE AND METHODS Body weight is the most extensively studied correlate of bone mass and is widely used as a covariate in statistical evaluations of bone mineral parameters .  Lean tissue mass ( LTM ) also correlates with bone mass . We evaluated the correlations linking each of these two parameters with bone mineral content and bone mineral density in 41 prepubertal girls , including ten swimmers , 18 gymnasts and 13 nonathletes .  Lean tissue mass , bone mineral content and bone mineral density were measured using dual-energy X-ray absorptiometry ( Hologic QDR-1000/W ; Hologic Inc. , Waltham , MA , USA ) . Forward stepwise multiple regression was used to evaluate correlations linking bone mineral content or density ( the dependent variables ) to body weight or lean tissue mass ( the independent variables ) . RESULTS Body weight and lean tissue mass showed strong correlations with all bone mineral content and density measurements in the simple linear regression analysis , with lean tissue mass yielding the highest Pearson 's correlation coefficients . In the multiple regression model , lean tissue mass consistently explained the largest proportion of the variance , whereas body weight had little influence or was eliminated from the model . The slopes of the regression lines of bone mineral content or density on body weight were significantly steeper in the subgroup of gymnasts ( P < 0.001 ) , whereas the slopes of the regression lines of bone mineral content or density on lean tissue mass were significantly less steep in the swimmers ( P < 0.05 ) . CONCLUSION Our data indicate that lean tissue mass is a significant predictor of bone mass in prepubertal girls and explains a larger part of the variance of bone mineral content and density than body weight . Use of body weight as a covariate in studies of bone mineral density may lead to erroneous results in prepubertal girls We have prospect ively studied forearm trabecular and cortical bone mineral density gain ( ΔBMD ) in relation to nutrient intake , weight‐bearing physical activity ( WPA ) and daylight exposure ( DE ) in 470 healthy boys and girls aged 8.2‐16.5 years at the baseline . BMD was assessed using single photon absorptiometry ( SPA ) . Cortical ΔBMD peaked at the age of 14.0 ± 0.3 and 16.0 ± 0.3 ( SD ) years in girls and boys , respectively . Girls had achieved adult premenopausal values of trabecular BMD by the age of 15 years and cortical BMD values by the age of 16.5 years . WPA , BMD , body height , height gain , weight , weight gain , dietary polyunsaturated 
    Output:
    
RESULTS It has been generally observed that swimmers present lower bone mineral density than athletes who practise high impact sports and similar values when compared to sedentary controls .
However , swimmers have a higher bone turnover than controls result ing in a different structure which in turn results in higher resistance to fracture indexes .
Nevertheless , swimming may become highly beneficial regarding bone mass in later stages of life .
Swimming does not seem to negatively affect bone mass , although it may not be one of the best sports to be practised in order to increase this parameter , due to the hypogravity and lack of impact characteristic of this sport .
However , swimmers present a higher bone turnover than sedentary controls that may result in a stronger structure and consequently in a stronger bone