Winning the battle against childhood physical inactivity: the key to bone strength?

The Effect of Primary School-Based Physical Education Programs: A Systematic Review of Randomized Controlled Trials

The present article aimed to systematically summarize primary school-based intervention programs and their effects evaluated through randomized-controlled trial design. A systematic review of relevant articles was carried out using 4 electronic databases. From a total of 193 studies initially found, 30 were included in the qualitative synthesis. Main results: (1) Intensive interval training or jump/strength exercises may positively influence physical fitness, promoting challenging task, psychological needs, and guided styles to a greater extent; (2) Games that demand more cognitive function seem more beneficial than those based on repetitive aerobic exertion to improve fundamental motor skills; (3) The jumping/strength exercises may cause benefits in bone area and bone mineral density, while flexibility and balance may reduce the risk of muscle injury; and (4) Programming a greater dose of moderate-to-vigorous physical activity seems to be related to positive effects in core executive function and academic performance. Additionally, providing information and involving the social environment may enhance the positive effects.

The Roles of RANK/RANKL/OPG in Cardiac, Skeletal, and Smooth Muscles in Health and Disease

Although their physiology and functions are very different, bones, skeletal and smooth muscles, as well as the heart have the same embryonic origin. Skeletal muscles and bones interact with each other to enable breathing, kinesis, and the maintenance of posture. Often, muscle and bone tissues degenerate synchronously under various conditions such as cancers, space travel, aging, prolonged bed rest, and neuromuscular diseases. In addition, bone tissue, skeletal and smooth muscles, and the heart share common signaling pathways. The RANK/RANKL/OPG pathway, which is essential for bone homeostasis, is also implicated in various physiological processes such as sarcopenia, atherosclerosis, and cardiovascular diseases. Several studies have reported bone-skeletal muscle crosstalk through the RANK/RANKL/OPG pathway. This review will summarize the current evidence indicating that the RANK/RANKL/OPG pathway is involved in muscle function. First, we will briefly discuss the role this pathway plays in bone homeostasis. Then, we will present results from various sources indicating that it plays a physiopathological role in skeletal, smooth muscle, and cardiac functions. Understanding how the RANK/RANKL/OPG pathway interferes in several physiological disorders may lead to new therapeutic approaches aimed at protecting bones and other tissues with a single treatment.

Targeting the Muscle-Bone Unit: Filling Two Needs with One Deed in the Treatment of Duchenne Muscular Dystrophy

PURPOSE OF REVIEW

In Duchenne muscular dystrophy (DMD), the progressive skeletal and cardiac muscle dysfunction and degeneration is accompanied by low bone mineral density and bone fragility. Glucocorticoids, which remain the standard of care for patients with DMD, increase the risk of developing osteoporosis. The scope of this review emphasizes the mutual cohesion and common signaling pathways between bone and skeletal muscle in DMD.

RECENT FINDINGS

The muscle-bone interactions involve bone-derived osteokines, muscle-derived myokines, and dual-origin cytokines that trigger common signaling pathways leading to fibrosis, inflammation, or protein synthesis/degradation. In particular, the triad RANK/RANKL/OPG including receptor activator of NF-kB (RANK), its ligand (RANKL), along with osteoprotegerin (OPG), regulates bone matrix modeling and remodeling pathways and contributes to muscle pathophysiology in DMD. This review discusses the importance of the muscle-bone unit in DMD and covers recent research aimed at determining the muscle-bone interactions that may eventually lead to the development of multifunctional and effective drugs for treating muscle and bone disorders regardless of the underlying genetic mutations in DMD.

Dietary Calcium Intake and Adherence to the Mediterranean Diet in Spanish Children: The ANIVA Study

The aim of this study was to evaluate the relationship of dietary calcium intake with anthropometric measures, physical activity and adherence to the Mediterranean diet (MedDiet) in 1176 Spanish children aged 6-9 years. Data were obtained from "Antropometría y Nutrición Infantil de Valencia" (ANIVA), a cross-sectional study of a representative sample. Dietary calcium intake assessed from three-day food records was compared to recommended daily intakes in Spain. Anthropometric measures (weight and height) were measured according to international standards and adherence to the MedDiet was evaluated using the Mediterranean Diet Quality Index (KIDMED) test. For the total sample of children, 25.8% had inadequate calcium intake, a significantly higher prevalence in girls (p = 0.006) and inadequate calcium intake was associated with lower height z-score (p = 0.001) for both sexes. In girls, there was an inverse relationship between calcium intake and body mass index (p = 0.001) and waist/hip ratio (p = 0.018). Boys presented a polarization in physical activity, reporting a greater level of both physical and sedentary activity in comparison with girls (p = 0.001). Children with poor adherence to MedDiet, even if they consume two yogurts or cheese (40 g) daily, adjusted by gender, age, total energy intake, physical activity and father's level of education, are at risk of inadequate total calcium intake (odds ratio adjusted [ORa]: 3.36, 95% confidence interval [CI]: 1.13-9.94, p = 0.001). The intake of these dairy products was insufficient to cover calcium intake recommendations in this age group (6-9 years). It is important to prioritize health strategies that promote the MedDiet and to increase calcium intake in this age group.

Differences in bone mineral density between normal-weight children and children with overweight and obesity: a systematic review and meta-analysis

OBJECTIVE

This study examines the differences in bone mineral density between normal-weight children and children with overweight or obesity.

METHODS

A systematic review and meta-analysis of observational studies (published up to 22 June 2016) on the differences in bone mineral density between normal-weight children and overweight and obese children was performed. Results were pooled when possible and mean differences (MDs) were calculated between normal-weight and overweight and normal-weight and obese children for bone content and density measures at different body sites.

RESULTS

Twenty-seven studies, with a total of 5,958 children, were included. There was moderate and high quality of evidence that overweight (MD 213 g; 95% confidence interval [CI] 166, 261) and obese children (MD 329 g; 95%CI [229, 430]) have a significantly higher whole body bone mineral content than normal-weight children. Similar results were found for whole body bone mineral density. Sensitivity analysis showed that the association was stronger in girls.

CONCLUSIONS

Overweight and obese children have a significantly higher bone mineral density compared with normal-weight children. Because there was only one study included with a longitudinal design, the long-term impact of childhood overweight and obesity on bone health at adulthood is not clear.

Developing CT based computational models of pediatric femurs

The mechanisms of fracture in infants and toddlers are not well understood. There have been very few studies on the mechanical properties of pediatric bones and their responses under fracture loading. A better understanding of fracture mechanisms in children will help elucidate both accidental and non-accidental injuries, as well as bone fragility diseases. The aim of this study is to develop in silico femoral models from CT scans to provide detailed quantitative information regarding the geometry and mechanical response of the femur, with the long term potential of investigating injury mechanisms. Fifteen anonymized QCT scans (aged 0-3 years) were collected and used to create personalized computational models of femurs. The elastic modulus of femur was illustrated at various ages. The models were also subjected to a series of four point bending simulations taking into account a range of loads perpendicular to the femoral shaft. The results showed that mid-shaft cross-section at birth appeared circular, but the diameter in the anteroposterior axis gradually increased with age. The density, and by implication modulus of elasticity at the mid-shaft became more differentiated with growth. Pediatric cortical bone with density close to the peak values found in adults was attained a few weeks after birth. The method is able to capture quantitative variations in geometries, material properties and mechanical responses, and has confirmed the rapid development of bone during the first few years of life using in silico models.

Influence of physical activity on bone strength in children and adolescents: a systematic review and narrative synthesis

A preponderance of evidence from systematic reviews supports the effectiveness of weight-bearing exercises on bone mass accrual, especially during the growing years. However, only one systematic review (limited to randomized controlled trials) examined the role of physical activity (PA) on bone strength. Thus, our systematic review extended the scope of the previous review by including all PA intervention and observational studies, including organized sports participation studies, with child or adolescent bone strength as the main outcome. We also sought to discern the skeletal elements (eg, mass, structure, density) that accompanied significant bone strength changes. Our electronic-database, forward, and reference searches yielded 14 intervention and 23 observational studies that met our inclusion criteria. We used the Effective Public Health Practice Project (EPHPP) tool to assess the quality of studies. Due to heterogeneity across studies, we adopted a narrative synthesis for our analysis and found that bone strength adaptations to PA were related to maturity level, sex, and study quality. Three (of five) weight-bearing PA intervention studies with a strong rating reported significantly greater gains in bone strength for the intervention group (3% to 4%) compared with only three significant (of nine) moderate intervention studies. Changes in bone structure (eg, bone cross-sectional area, cortical thickness, alone or in combination) rather than bone mass most often accompanied significant bone strength outcomes. Prepuberty and peripuberty may be the most opportune time for boys and girls to enhance bone strength through PA, although this finding is tempered by the few available studies in more mature groups. Despite the central role that muscle plays in bones' response to loading, few studies discerned the specific contribution of muscle function (or surrogates) to bone strength. Although not the focus of the current review, this seems an important consideration for future studies.

Does physical activity in adolescence have site-specific and sex-specific benefits on young adult bone size, content, and estimated strength?

The long-term benefits of habitual physical activity during adolescence on adult bone structure and strength are poorly understood. We investigated whether physically active adolescents had greater bone size, density, content, and estimated bone strength in young adulthood when compared to their peers who were inactive during adolescence. Peripheral quantitative computed tomography (pQCT) was used to measure the tibia and radius of 122 (73 females) participants (age mean ± SD, 29.3 ± 2.3 years) of the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS). Total bone area (ToA), cortical density (CoD), cortical area (CoA), cortical content (CoC), and estimated bone strength in torsion (SSIp ) and muscle area (MuA) were measured at the diaphyses (66% tibia and 65% radius). Total density (ToD), trabecular density (TrD), trabecular content (TrC), and estimated bone strength in compression (BSIc ) were measured at the distal ends (4%). Participants were grouped by their adolescent physical activity (PA) levels (inactive, average, and active) based on mean PA Z-scores obtained from serial questionnaire assessments completed during adolescence. We compared adult bone outcomes across adolescent PA groups in each sex using analysis of covariance followed by post hoc pairwise comparisons with Bonferroni adjustments. When adjusted for adult height, MuA, and PA, adult males who were more physically active than their peers in adolescence had 13% greater adjusted torsional bone strength (SSIp , p < 0.05) and 10% greater adjusted ToA (p < 0.05) at the tibia diaphysis. Females who were more active in adolescence had 10% larger adjusted CoA (p < 0.05), 12% greater adjusted CoC (p < 0.05) at the tibia diaphysis, and 3% greater adjusted TrC (p < 0.05) at the distal tibia when compared to their inactive peers. Benefits to tibia bone size, content, and strength in those who were more active during adolescence seemed to persist into young adulthood, with greater ToA and SSIp in males, and greater CoA, CoC, and TrC in females.

Dystrophin and utrophin "double knockout" dystrophic mice exhibit a spectrum of degenerative musculoskeletal abnormalities

Duchenne muscular dystrophy (DMD) is a degenerative muscle disorder characterized by the lack of dystrophin expression at the sarcolemma of muscle fibers. In addition, DMD patients acquire osteopenia, fragility fractures, and scoliosis indicating that a deficiency in skeletal homeostasis coexists but little is known about the effects of DMD on bone and other connective tissues within the musculoskeletal system. Recent evidence has emerged implicating adult stem cell dysfunction in DMD myopathogenesis. Given the common mesenchymal origin of muscle and bone, we sought to investigate bone and other musculoskeletal tissues in a DMD mouse model. Here, we report that dystrophin-utrophin double knockout (dko) mice exhibit a spectrum of degenerative changes, outside skeletal muscle, in bone, articular cartilage, and intervertebral discs, in addition to reduced lifespan, muscle degeneration, spinal deformity, and cardiomyopathy previously reported. We also report these mice to have a reduced capacity for bone healing and exhibit spontaneous heterotopic ossification in the hind limb muscles. Therefore, we propose the dko mouse as a model for premature musculoskeletal aging and posit that a similar phenomenon may occur in patients with DMD.

Forum on aging and skeletal health: summary of the proceedings of an ASBMR workshop

With the aging of the population, the scope of the problem of age-related bone loss and osteoporosis will continue to increase. As such, it is critical to obtain a better understanding of the factors determining the acquisition and loss of bone mass from childhood to senescence. While there have been significant advances in recent years in our understanding of both the basic biology of aging and a clinical definition of age-related frailty, few of these concepts in aging research have been evaluated adequately for their relevance and application to skeletal aging or fracture prevention. The March 2011 Forum on Aging and Skeletal Health, sponsored by the NIH and ASBMR, sought to bring together leaders in aging and bone research to enhance communications among diverse fields of study so as to accelerate the pace of scientific advances needed to reduce the burden of osteoporotic fractures. This report summarizes the major concepts presented at that meeting and in each area identifies key questions to help set the agenda for future research in skeletal aging.

Non-pharmacological management of osteoporosis: a consensus of the Belgian Bone Club

This consensus article reviews the various aspects of the non-pharmacological management of osteoporosis, including the effects of nutriments, physical exercise, lifestyle, fall prevention, and hip protectors. Vertebroplasty is also briefly reviewed. Non-pharmacological management of osteoporosis is a broad concept. It must be viewed as an essential part of the prevention of fractures from childhood through adulthood and the old age. The topic also includes surgical procedures for the treatment of peripheral and vertebral fractures and the post-fracture rehabilitation. The present document is the result of a consensus, based on a systematic review and a critical appraisal of the literature. Diets deficient in calcium, proteins or vitamin D impair skeletal integrity. The effect of other nutriments is less clear, although an excessive consumption of sodium, caffeine, or fibres exerts negative effects on calcium balance. The deleterious effects of tobacco, excessive alcohol consumption and a low BMI are well accepted. Physical activity is of primary importance to reach optimal peak bone mass but, if numerous studies have shown the beneficial effects of various types of exercise on bone mass, fracture data as an endpoint are scanty. Fall prevention strategies are especially efficient in the community setting, but less evidence is available about their effectiveness in preventing fall-related injuries and fractures. The efficacy of hip protectors remains controversial. This is also true for vertebroplasty and kyphoplasty. Several randomized controlled studies had reported a short-term advantage of vertebroplasty over medical treatment for pain relief, but these findings have been questioned by recent sham-controlled randomized clinical studies.

Effect of a general school-based physical activity intervention on bone mineral content and density: a cluster-randomized controlled trial

BACKGROUND

Specific physical loading leads to enhanced bone development during childhood. A general physical activity program mimicking a real-life situation was successful at increasing general physical health in children. Yet, it is not clear whether it can equally increase bone mineral mass. We performed a cluster-randomized controlled trial in children of both gender and different pubertal stages to determine whether a school-based physical activity (PA) program during one school-year influences bone mineral content (BMC) and density (BMD), irrespective of gender.

METHODS

Twenty-eight 1st and 5th grade (6-7 and 11-12 year-old) classes were cluster randomized to an intervention (INT, 16 classes, n=297) and control (CON; 12 classes, n=205) group. The intervention consisted of a multi-component PA intervention including daily physical education with at least 10 min of jumping or strength training exercises of various intensities. Measurements included anthropometry, and BMC and BMD of total body, femoral neck, total hip and lumbar spine using dual-energy X-ray absorptiometry (DXA). PA was assessed by accelerometers and Tanner stages by questionnaires. Analyses were performed by a regression model adjusted for gender, baseline height and weight, baseline PA, post-intervention pubertal stage, baseline BMC, and cluster.

RESULTS

275 (72%) of 380 children who initially agreed to have DXA measurements had also post-intervention DXA and PA data. Mean age of prepubertal and pubertal children at baseline was 8.7±2.1 and 11.1±0.6 years, respectively. Compared to CON, children in INT showed statistically significant increases in BMC of total body, femoral neck, and lumbar spine by 5.5%, 5.4% and 4.7% (all p<0.05), respectively, and BMD of total body and lumbar spine by 8.4% and 7.3% (both p<0.01), respectively. There was no gender *group, but a pubertal stage *group interaction consistently favoring prepubertal children.

CONCLUSION

A general school-based PA intervention can increase bone health in elementary school children of both genders, particularly before puberty.

Low bone density and bone metabolism alterations in Duchenne muscular dystrophy: response to calcium and vitamin D treatment

Boys with Duchenne muscular dystrophy often have reduced bone mass and increased fracture risk. In this prospective study on 33 patients, calcifediol (25-OH vitamin D(3)) plus adjustment of dietary calcium to the recommended dose reduced bone resorption, corrected vitamin D deficiency, and increased bone mass in about two-thirds of cases.

INTRODUCTION

Low BMC and BMD and bone metabolism alterations are frequent in boys with Duchenne muscular dystrophy (DMD), especially now that long-term glucocorticosteroid (GC) treatment is the standard of care. This prospective study was designed to evaluate the effects of a first-line treatment (25-OH vitamin D(3) [calcifediol] plus adjustment of dietary calcium to the recommended daily dose) on bone.

METHODS

Thirty-three children with DMD on GC treatment were followed for 3 years: one of observation and two of treatment.

MAIN OUTCOME

spine and total body BMC and BMD increase; secondary outcome: changes in bone turnover markers (C-terminal [CTx] and N-terminal [NTx] telopeptides of procollagen type I; osteocalcin [OC]).

RESULTS

During the observation year, BMC and BMD decreased in all patients. At baseline and after 12 months, serum CTx and urinary NTx were higher than normal; OC and parathyroid hormone at the upper limit of normal; 25-OH vitamin D(3) significantly lower than normal. After 2 years of calcifediol and calcium-rich diet, BMC and BMD significantly increased in over 65% of patients, and bone metabolism parameters and turnover markers normalized in most patients (78.8%). During the observation year, there were four fractures in four patients, while during the 2 years of treatment there were two fractures in two patients.

CONCLUSIONS

Calcifediol plus adequate dietary calcium intake seems to be an effective first-line approach that controls bone turnover, corrects vitamin D deficiency, and increases BMC and BMD in most patients with DMD. Lack of response seems related to persistently high bone turnover.

Clinical report—bone densitometry in children and adolescents

Concern for bone fragility in children and adolescents has led to increased interest in bone densitometry. Pediatric patients with genetic and acquired chronic diseases, immobility, and inadequate nutrition may fail to achieve the expected gains in bone size, mass, and strength, which leaves them vulnerable to fracture. In older adults, bone densitometry has been shown to predict fracture risk and reflect response to therapy. The role of densitometry in the management of children at risk of bone fragility is less certain. This clinical report summarizes the current knowledge about bone densitometry in the pediatric population, including indications for its use, interpretation of results, and its risks and costs. This report emphasizes consensus statements generated at the 2007 Pediatric Position Development Conference of the International Society of Clinical Densitometry by an international panel of bone experts. Some of these recommendations are evidence-based, and others reflect expert opinion, because the available data are inadequate. The statements from this and other expert panels have provided general guidance to the pediatrician, but decisions about ordering and interpreting bone densitometry still require clinical judgment. Ongoing studies will help to better define the indications and best methods for assessing bone strength in children and the clinical factors that contribute to fracture risk.

Secular trends in muscular fitness among Finnish adolescents

AIM

To investigate secular change over time in health-related muscular fitness and how leisure time physical activity (LTPA), sport club participation, and body mass index are associated with muscular fitness in adolescents.

METHODS

Two cross-sectional samples of Finnish 13-16-year-old adolescents were studied in 1976 (n = 643; 312 boys and 331 girls) and in 2001 (n = 579; 308 boys and 271 girls). Muscular fitness index was calculated as the sum of age- and sex-specific z-scores of four tests measuring muscular fitness and agility. Height and weight were also measured. Self-reported weekly frequency of LTPA of at least 30-min duration and regularity of participation in organised sport were obtained by questionnaire. Identical methods were used in 1976 and 2001.

RESULTS

Muscular fitness index was higher in 2001 than in 1976 in both boys (by 0.77 points, p = 0.008, effect size d = 0.17, small difference) and girls (1.01 points, p = 0.004, d = 0.20, small difference). Sport club participation, body mass index, and participation in LTPA together explained more of the muscular fitness index variance in 2001 than in 1976 in both boys (coefficient of determination from 0.10 to 0.24) and girls (from 0.25 to 0.40).

CONCLUSIONS

The muscular fitness of 13-16-year old adolescents slightly improved over time. Organised LTPA showed a stronger association with muscular fitness in 2001 than in 1976. Due to increased polarisation in fitness, in health promotion more attention should be paid on adolescents' health-related fitness and its association to LTPA.

Familial resemblance of bone mineral density in children with inflammatory bowel disease

BACKGROUND AND AIM

Low bone mineral density (BMD) has recently been recognized as a potential health problem in children with inflammatory bowel disease (IBD). Our aim was to investigate the familial resemblance of BMD in pediatric patients with IBD.

PATIENTS AND METHODS

In this population-based study from western Sweden, we assessed 144 children with IBD, 83 with ulcerative colitis, 45 with Crohn disease, 16 with indeterminate colitis, and their parents (136 mothers and 130 fathers) with dual-energy X-ray absorptiometry (DEXA). After adjustment for sex, age, weight, height, and parental IBD, we correlated the BMD of the patients to the BMD of their mothers, fathers, and the midparent value ([mother's BMD + father's BMD]/2) at different skeletal sites and calculated the Pearson correlation coefficient (r) to evaluate the extent of familial resemblance.

RESULTS

The BMD of the children with IBD was clearly related to the BMD of their parents. The strongest correlation was found in the femoral neck with r = 0.55 (P < 0.001, 95% CI 0.41-0.66) between BMD of the children and the midparent value. The group of children with IBD had an odds ratio of 5.96 for decreased BMD (lumbar spine z score < -1 standard deviation) given that decreased BMD was diagnosed in both parents.

CONCLUSIONS

We conclude that BMD in children and adolescents with IBD is significantly related to that of their parents. In a clinical setting, it may be helpful to assess the parents of children with IBD with DEXA to interpret the children's DEXA measurements.

Bone mineral accrual across growth in a mixed-ethnic group of children: are Asian children disadvantaged from an early age?

We investigated the contribution of ethnicity, physical activity, body composition, and calcium intake to bone accrual across 7 years of growth. We assessed 80 Caucasian and 74 Asian boys and 81 Caucasian and 64 Asian girls at baseline and retained 155 children across all 7 years. Ethnicity, physical activity, and calcium intake were assessed by questionnaire; fat mass, lean mass, and bone mineral content (BMC) of the whole body (WB), lumbar spine (LS), total proximal femur (PF(TOT)), and femoral neck (FN) were measured using DXA (Hologic QDR 4500). We aligned children on peak height velocity and utilized multilevel modeling to assess bone mineral accrual. Height and lean mass accounted for 51.8% and 44.1% of BMC accrual in children. There was a significant difference in physical activity, calcium intake, and lean mass between Asians and Caucasian boys and girls at baseline and conclusion (p < 0.05). In boys, physical activity and ethnicity significantly predicted BMC accrual at the FN. In girls, Asians had significantly lower PF(TOT) and FN BMC. Calcium was a significant predictor of WB BMC accrual in boys and girls. In conclusion, our findings highlight the importance of accounting for ethnicity in pediatric studies. Physical activity, dietary calcium, and lean mass positively influence bone accrual and are lower in Asian compared to Caucasian children from a very young age.

A longitudinal study of the relationship of physical activity to bone mineral accrual from adolescence to young adulthood

Physical activity in adolescence is beneficial for increasing bone mineral accrual; however, it's unclear whether these benefits persist into adulthood. This prospective 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 questionnaire 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.