Former college artistic gymnasts maintain higher BMD: a nine-year follow-up

Introduction If higher bone gains acquired from weight-bearing sports during growth persist into old age, the residual benefits could delay or even prevent osteoporotic fractures. The purpose of this study was to determine if the higher areal bone mineral density (aBMD) observed 15 years after competitive training and competition in former female college artistic gymnasts (GYM) compared with controls (CON) is maintained nine years later in this same cohort approaching menopause. In this 9-year follow-up, aBMD changes were also compared between GYM (n=16; aged 45.3±3.3 years) and CON (n=13; aged 45.4±3.8 years).Methods Total body, lumbar spine, proximal femur, femoral neck, leg, and arm aBMD were assessed at baseline and follow-up using dual-energy X-ray absorptiometry (DXA), (Hologic QDR-1000W). GYM had higher aBMD at all sites at follow-up (P<0.05; η ²>0.14).Results While there were no significant differences between groups for percent changes in aBMD at the total body, lumbar spine, total proximal femur, femoral neck, and arm, the change in leg aBMD was significantly different between GYM and CON (P=0.05; η ²=0.14).Conclusions Former female college artistic gymnasts maintained significantly higher aBMD than controls 24 years after retirement from gymnastics training and competition. This study provides greater insight into the effects of past athletic participation on skeletal health in women approaching menopause.Funding sources: The University of Georgia College of Family and Consumer Sciences.     

Bone density,body composition and menstrual history of sedentary female former gymnasts,aged 20–32 years

Few studies have examined the effects of retirement from sports involving regular, high impact and weight bearing activity on bone mass. This cross-sectional study compared total body and regional areal bone mineral density (aBMD, g/cm²) within female former gymnasts and women who had never participated in structured sport or exercise, and explored relations between aBMD of these former gymnasts and their duration of retirement. Eighteen sedentary female former gymnasts (GYM) and 18 sedentary controls (CON) were recruited. GYM displayed a broad range of duration of retirement (3–12 years) and a wide age range (20–32 years). GYM and CON were paired individually to match for age, body mass and stature. GYM had commenced training at least 3 years pre-menarche and had trained post-menarche for 2 or more years. They had trained continuously for 5–12 years and had retired between age 14 and 22 years. Measurements of aBMD and body composition were made using dual energy X-ray absorptiometry (DXA). Group mean values of physical and skeletal characteristics were compared using paired t-tests. Linear regression was used to explore possible relations of aBMD within GYM to duration of retirement. GYM displayed a higher aBMD than CON at all measurement sites, which ranged in magnitude from 6% for the total body (P=0.004), to 11% for the total femur (P=0.006). Elevations of aBMD within GYM equated to T-scores ranging from +0.8 (arms) to +1.7 (legs). There were no differences in body composition or age of menarche between groups, although 11 of 18 GYM reported a history of irregular menses. There was no significant decline of aBMD with increasing duration of retirement in GYM. The results suggested that an elevated bone mass in female former gymnasts was retained during early adulthood, in spite of a cessation of training for up to 12 years.     

女性年龄相关的腰椎骨量与骨骼大小的关系及对诊断骨质疏松的影响

目的探讨腰椎骨量(面积骨密度和体积骨密度)与年龄和骨骼骨面积(BA)大小之间的关系,及腰椎骨骼大小对评价骨量和诊断骨质疏松(OP)的影响。方法采用QDR-4500A型扇形束双能X线吸收法骨密度仪,测量5585例年龄5～96岁的女性正位腰椎BA、骨矿含量(BMC)、面积骨密度(aBMD)及估算体积骨密度(vBMD)。结果腰椎aBMD和vBMD的峰值BMD(x珋±s)分别为0.9884±0.1064g/cm2和0.1310±0.0128g/cm3。在所有年龄阶段aBMD随年龄的变化率显著大于vBMD。腰椎BA与BMC、aBMD和vBMD均呈显著正相关,其中BA与BMC的相关系数最大(r=0.706,P=0.000),与aBMD的相关系数次之(r=0.394,P=0.000),与vBMD的相关系数最小(r=0.141,P=0.000)。年龄≥40岁(平均52.7±9.58岁)的受试者(n=4012)腰椎BA按四分位数分成Q1、Q2、Q3和Q4组,4个组之间的BA、BMC和aBMD的平均值均有显著性差异。采用aBMD诊断OP,4个组的OP检出率分别为Q1=33.6%、Q2=17.9%、Q3=13.3%和Q4=8.39%,呈显著性梯次降低;与总体组比较,Q1组的患病风险增加126%,Q2、Q3和Q4组的患病风险分别降低3%、31%和59%。采用vBMD诊断OP,4个组的OP检出率分别为Q1=27.4%、Q2=18.3%、Q3=15.9%和Q4=14.0%,其梯次差异显著低于aBMD;与总体组比较,Q1组的患病风险增加62%,Q2、Q3和Q4组的患病风险分别降低4%、19%和30%。Q1组aBMD的OP检出率显著高于vBMD,Q4组aBMD的OP检出率显著低于vBMD。在椎体最小的Q1组,aBMD(OR=2.26)的患病风险比vBMD(OR=1.62)大约高64%,在椎体最大的Q4组,aBMD(OR=0.41)的患病风险比vBMD(OR=0.70)大约低29%。结论该研究揭示腰椎vBMD并不能完全消除骨骼大小对评价骨量和诊断OP的影响。在腰椎椎体较小的受试者,aBMD诊断OP的敏感性高于vBMD;在椎体较大的受试者,vBMD诊断OP的敏感性则高于aBMD。     

Correcting Fan-Beam Magnification in Clinical Densitometry Scans of Growing Subjects

As children grow, body and limb girths increase. For serial densitometric measurements, growth increases the distance between the bone region of interest and X-ray source over time, thereby increasing fan-beam magnification. To isolate bone accrual from magnification error in growing subjects, we developed a correction method based on waist girth, a common anthropometric measure. This correction was applied to dual-energy X-ray absorptiometry output obtained in a cohort of premenarcheal gymnasts and nongymnasts. After correcting for magnification, results for projected area and bone mineral content (BMC) increased by 0.4–1.1% at the lumbar spine and 8–16% at the femoral neck, decreasing areal bone mineral density (aBMD) by 0.4–2.3% at both sites. The effects of magnification correction were similar in magnitude to BMC and aBMD gains previously reported in longitudinal studies of normoactive children. Because of body size differences, the effect of correction for BMC and aBMD was 10–20% greater in nongymnasts than in gymnasts, which increased the observed aBMD differential between gymnasts and nongymnasts. Fan-beam magnification distorts true changes in bone mineral measures in growing premenarcheal girls and, therefore, may obscure additional activity-related changes during growth. Our correction technique may enhance detection of skeletal adaptation, particularly in pediatric populations.     

Bone mineral content and density of the lumbar spine of infants and toddlers: Influence of age,sex, race,growth, and human milk feeding

Little is known about factors that affect bone mass and density of infants and toddlers and the means to assess their bone health owing to challenges in studying this population. The objectives of this study were to describe age, sex, race, growth, and human milk feeding effects on bone mineral content (BMC) and areal density (aBMD) of the lumbar spine, and determine precision of BMC and aBMD measurements. We conducted a cross‐sectional study of 307 healthy participants (63 black), ages 1 to 36 months. BMC and aBMD of the lumbar spine were measured by dual‐energy X‐ray absorptiometry. Duplicate scans were obtained on 76 participants for precision determination. Age‐specific Z‐scores for aBMD, weight, and length (BMDZ, WAZ, LAZ) were calculated. Information on human milk feeding duration was ascertained by questionnaire. Between ages 1 and 36 months, lumbar spine BMC increased about fivefold and aBMD increased twofold (p < 0.0001). BMC was greater (5.8%) in males than in females (p = 0.001), but there was no difference in aBMD (p = 0.37). There was no difference in BMC or aBMD between whites and blacks (p ≥ 0.16). WAZ and LAZ were positively associated with BMDZ (r = 0.34 and 0.24, p < 0.001). Duration of human milk feeding was negatively associated with BMDZ in infants <12 months of age (r = ?0.42, p < 0.001). Precision of BMC and aBMD measurements was good, 2.20% and 1.84%, respectively. Dramatic increases in BMC and aBMD of the lumbar spine occur in the first 36 months of life. We provide age‐specific values for aBMD of healthy infants and toddlers that can be used to evaluate bone deficits. Future studies are needed to identify the age when sex and race differences in aBMD occur, and how best to account for delayed or accelerated growth in the context of bone health assessment of infants and toddlers. © 2013 American Society for Bone and Mineral Research     

Bone mineral accrual in 4‐ to 10‐year‐old precompetitive,recreational gymnasts: A 4‐year longitudinal study

Competitive female gymnasts have greater bone mineral measures than nongymnasts. However, less is known about the effect of recreational and/or precompetitive gymnastics participation on bone development. The purpose of this study was to investigate whether the differences previously reported in the skeleton of competitive female gymnasts are also demonstrated in young children with a current or past participation history in recreational or precompetitive gymnastics. One hundred and sixty‐three children (30 gymnasts, 61 ex‐gymnasts, and 72 nongymnasts) between 4 and 6 years of age were recruited and measured annually for 4 years (not all participants were measured at every occasion). Total‐body (TB), lumbar spine (LS), and femoral neck (FN) bone mineral content (BMC) were measured by dual‐energy X‐ray absorptiometry (DXA). Multilevel random‐effects models were constructed and used to predict differences in TB, LS, and FN BMC between groups while controlling for differences in body size, physical activity, and diet. Gymnasts had 3% more TB and 7% more FN BMC than children participating in other recreational sports at year 4 (p < .05). No differences were found at the LS between groups, and there were no differences between ex‐gymnasts' and nongymnasts' bone parameters (p > .05). These findings suggest that recreational and precompetitive gymnastics participation is associated with greater BMC. This is important because beginner gymnastics skills are attainable by most children and do not require a high level of training. Low‐level gymnastics skills can be implemented easily into school physical education programs, potentially affecting skeletal health. © 2011 American Society for Bone and Mineral Research.     

Romosozumab improves lumbar spine bone mass and bone strength parameters relative to alendronate in postmenopausal women: results from the Active-Controlled Fracture Study in Postmenopausal Women With Osteoporosis at High Risk (ARCH) trial

The Active-Controlled Fracture Study in Postmenopausal Women With Osteoporosis at High Risk (ARCH) trial (NCT01631214; https://clinicaltrials.gov/ct2/show/NCT01631214 ) showed that romosozumab for 1 year followed by alendronate led to larger areal bone mineral density (aBMD) gains and superior fracture risk reduction versus alendronate alone. aBMD correlates with bone strength but does not capture all determinants of bone strength that might be differentially affected by various osteoporosis therapeutic agents. We therefore used quantitative computed tomography (QCT) and finite element analysis (FEA) to assess changes in lumbar spine volumetric bone mineral density (vBMD), bone volume, bone mineral content (BMC), and bone strength with romosozumab versus alendronate in a subset of ARCH patients. In ARCH, 4093 postmenopausal women with severe osteoporosis received monthly romosozumab 210 mg sc or weekly oral alendronate 70 mg for 12 months, followed by open-label weekly oral alendronate 70 mg for ≥12 months. Of these, 90 (49 romosozumab, 41 alendronate) enrolled in the QCT/FEA imaging substudy. QCT scans at baseline and at months 6, 12, and 24 were assessed to determine changes in integral (total), cortical, and trabecular lumbar spine vBMD and corresponding bone strength by FEA. Additional outcomes assessed include changes in aBMD, bone volume, and BMC. Romosozumab caused greater gains in lumbar spine integral, cortical, and trabecular vBMD and BMC than alendronate at months 6 and 12, with the greater gains maintained upon transition to alendronate through month 24. These improvements were accompanied by significantly greater increases in FEA bone strength (p < 0.001 at all time points). Most newly formed bone was accrued in the cortical compartment, with romosozumab showing larger absolute BMC gains than alendronate (p < 0.001 at all time points). In conclusion, romosozumab significantly improved bone mass and bone strength parameters at the lumbar spine compared with alendronate. These results are consistent with greater vertebral fracture risk reduction observed with romosozumab versus alendronate in ARCH and provide insights into structural determinants of this differential treatment effect. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).     

Site-specific,adult bone benefits attributed to loading during youth: A preliminary longitudinal analysis

We examined site-specific bone development in relation to childhood and adolescent artistic gymnastics exposure, comparing up to 10 years of prospectively acquired longitudinal data in 44 subjects, including 31 non-gymnasts (NON) and 13 gymnasts (GYM) who participated in gymnastics from pre-menarche to ≥ 1.9 years post-menarche. Subjects underwent annual regional and whole-body DXA scans; indices of bone geometry and strength were calculated. Anthropometrics, physical activity, and maturity were assessed annually, coincident with DXA scans. Non-linear mixed effect models centered growth in bone outcomes at menarche and adjusted for menarcheal age, height, and non-bone fat-free mass to evaluate GYM-NON differences. A POST-QUIT variable assessed the withdrawal effect of quitting gymnastics. Curves for bone area, mass (BMC), and strength indices were higher in GYM than NON at both distal radius metaphysis and diaphysis (p < 0.0001). At the femoral neck, greater GYM BMC (p < 0.01), narrower GYM endosteal diameter (p < 0.02), and similar periosteal width (p = 0.09) yielded GYM advantages in narrow neck cortical thickness and buckling ratio (both p < 0.001; lower BR indicates lower fracture risk). Lumbar spine and sub-head BMC were greater in GYM than NON (p < 0.036). Following gymnastics cessation, GYM slopes increased for distal radius diaphysis parameters (p ≤ 0.01) and for narrow neck BR (p = 0.02). At the distal radius metaphysis, GYM BMC and compressive strength slopes decreased, as did slopes for lumbar spine BMC, femoral neck BMC, and narrow neck cortical thickness (p < 0.02). In conclusion, advantages in bone mass, geometry, and strength at multiple skeletal sites were noted across growth and into young adulthood in girls who participated in gymnastics loading to at least 1.9 years post-menarche. Following gymnastics cessation, advantages at cortical bone sites improved or stabilized, while advantages at corticocancellous sites stabilized or diminished. Additional longitudinal observation is necessary to determine whether residual loading benefits enhance lifelong skeletal strength.     

Higher premenarcheal bone mass in elite gymnasts is maintained into young adulthood after long‐term retirement from sport: A 14‐year follow‐up

Sports that impact‐load the skeleton during childhood and adolescence increase determinants of bone strength such as bone mineral content and density; however, it is unclear if this benefit is maintained after retirement from the sport. The purpose of this study was to assess whether the previously reported higher bone mass in a group of premenarcheal gymnasts was still apparent 10 years after the cessation of participation and withdrawal of the gymnastics loading stimulus. In 1995, 30 gymnasts 8 to 15 years of age were measured and compared with 30 age‐matched nongymnasts. Twenty‐five former gymnasts and 22 nongymnasts were measured again 14 years later (2009 to 2010). Gymnasts had been retired from gymnastics training and competition for an average of 10 years. Total body (TB), lumbar spine (LS), and femoral neck (FN) bone mineral content (BMC) was assessed at both measurement occasions by dual‐energy X‐ray absorptiometry (DXA). Multivariate analysis of covariance (MANCOVA) was used to compare former gymnasts' and nongymnasts' BMC while controlling for differences in body size and maturation (covariates: age, height, weight, and years from menarche [1995] or age at menarche [2009 to 2010]). Premenarcheal gymnasts (measured in 1995) had significantly greater size‐adjusted TB, LS, and FN BMC (p < 0.05) (15%, 17%, and 12%, respectively) than nongymnasts. Ten years after retirement, gymnasts had maintained similar size‐adjusted TB, LS, and FN BMC differences (p < 0.05) (13%, 19%, and 13%, respectively) when compared with nongymnasts. Bone mass benefits in premenarcheal gymnasts were still apparent even after long‐term (10 years) removal of the gymnastics loading stimulus. © 2012 American Society for Bone and Mineral Research     

Effects of skeletal size of the lumbar spine on areal bone density,volumetric bone density,and the diagnosis of osteoporosis in postmenopausal women in China

To understand the effects of skeletal size of the lumbar spine on areal bone mineral density (aBMD), volumetric bone mineral density (vBMD), and the diagnosis of osteoporosis in postmenopausal women, we measured the projected bone area, bone mineral content (BMC), aBMD, and vBMD at the anteroposterior and lateral lumbar spines in a population of 1081 postmenopausal Chinese women, 42 to 86 years of age. The results indicated that, at the anteroposterior and lateral lumbar spine, there were significant positive correlations between bone area and both BMC (r = 0.606; P = 0.000 and r = 0.610; P = 0.000) and aBMD (r = 0.270; P = 0.000 and r = 0.182; P = 0.000), but not vBMD (r = –0.055; P = 0.000 and r = 0.000; P = 0.929). When bone area at the anteroposterior spine changed by ±1 SD, the BMC, aBMD, and vBMD correspondingly changed by 28.2%, 10.1%, and 1.69% on the basis of their respective means. When a variation of ±1 SD was observed in bone area at the lateral spine, BMC and aBMD, correspondingly changed by 25.9% and 6.18% on the basis of their respective means, while vBMD indicated no change. Through comparisons among large-, intermediate-, and small-bone area groups, significant differences were found in the means of subjects heights, weights, BMC, and vBMD at the anteroposterior and lateral lumbar spines, as well as in the detection rates of osteoporosis by aBMD (P = 0.000). Detection rates of osteoporosis by aBMD at the anteroposterior spine and by aBMD at the lateral spine, and by vBMD were 44.1%, 55.5%, and 49.7%, respectively, in the total population; 31.4%, 41.7%, and 53.7%, respectively, in the large-bone area group; 43.3%, 55.9%, and 50.5%, respectively, in the intermediate-bone area group; and 61.7%, 70.0%, and 42.5%, respectively, in the small-bone area group. No significant differences were found in the detection rates of osteoporosis by vBMD among the groups. The results of multiple linear regression revealed that the major factors influencing skeletal size and aBMD of the lumbar spine were height and weight. Therefore, in menopausal women of the same ethnic group and age, the skeletal size of the lumbar spine would have significant influence upon aBMD and the diagnosis of osteoporosis, i.e., the larger the spinal size, the greater the aBMD and the lower the osteoporosis detection rate, while, conversely, the smaller the skeletal size, the smaller the aBMD and the higher the osteoporosis detection rate. When we use aBMD of the lumbar spine to diagnose osteoporosis in a population with different body sizes, we need to take this body size difference into account. When we use vBMD to diagnose osteoporosis, the effect of body size on BMD will diminish.     

Trabecular bone microarchitecture in female collegiate gymnasts

SUMMARY: Using high-resolution magnetic resonance imaging, we observed more developed trabecular bone microarchitecture in the proximal tibia of female collegiate gymnasts vs. matched controls. This suggests that high-load physical activity may have a positive effect on the trabecular microarchitecture in weight-bearing bone. INTRODUCTION: Participation in physical activities that overload the skeleton, such as artistic gymnastics, is associated with increased areal bone mineral density (aBMD); however, the status of trabecular microarchitecture in the weight-bearing bone of gymnasts is unknown. METHODS: Eight female collegiate artistic gymnasts and eight controls matched for age, height, body mass, gender and race were recruited for the study. Apparent trabecular bone volume to total volume (appBV/TV), trabecular number (appTb.N), thickness (appTb.Th) and trabecular separation (appTb.Sp) were determined using high resolution magnetic resonance imaging. Areal bone mineral density, bone mineral content (BMC) and bone area in the proximal tibia were determined using dual-energy X-ray absorptiometry. Group differences were determined using t-tests. The magnitude of group differences was expressed using Cohen's d (d). RESULTS: Gymnasts had higher appBV/TV (13.6%, d = 1.22) and appTb.N (8.4%, d = 1.45), and lower appTb.Sp (13.7%, d = 1.33) than controls (p < 0.05). Gymnasts had higher aBMD and BMC in the proximal tibia, although the differences were smaller in magnitude (d = 0.75 and 0.74, respectively) and not statistically significant (p > 0.05). CONCLUSION: The findings suggest that high-load physical activity, such as performed during gymnastics training, may enhance the trabecular microarchitecture of weight-bearing bone.     

Frame size, ethnicity, lifestyle, and biologic contributors to areal and volumetric lumbar spine bone mineral density in Indian/Pakistani and American Caucasian premenopausal women.

Published data on the spinal bone mineral density (BMD) of premenopausal women originating from the Indian subcontinent (Indian/Pakistani) are few. We compared anteroposterior (AP) and lateral areal BMD (aBMD) using dual X-ray absorptiometry and calculated volumetric BMD (vBMD) in Indian/Pakistani (n = 47) vs American (n = 47) women with dissimilar statures and skeletal sizes. To account for differences, we "adjusted" lumbar aBMD separately for vertebral size (aBMD/the square root of the projected area), height (aBMD/height), and hip skeletal width (aBMD/hip width). We "corrected" bone mineral content (BMC), aBMD, and vBMD for frame size, collectively using height, hip width, and vertebral size. Unadjusted mean aBMD values for AP lumbar (L1-L4, p = 0.0086; L3-L4, p = 0.044) spine were higher in Americans than Indians/Pakistanis,whereas lateral vBMD (p = 0.56) or aBMD (p = 0.060) values were not different. After adjusting for height, hip width, or vertebral size, or correcting for frame size, differences in aBMD disappeared. Regression analyses indicated that the best measures to correct for frame size were: vertebral area for BMC, hip width for aBMD, and vertebral width for lateral vBMD. Height was not significant in any model. In correcting for frame size, we accounted for 73-85% of the variability in BMC, 22-28% in aBMD, and 27% in lateral vBMD. After frame size was corrected, we accounted for 34% of the variability in AP BMC and aBMD, in contrast with 6-9% in the lateral models. Five significant biologic and lifestyle factors remained in AP models; only body weight remained for lateral spine. Upon accounting for frame size using regression, much variability in BMD, aBMD, and vBMD was explained by lifestyle and biologic factors, not by ethnicity.     

Catch up in bone acquisition in young adult men with late normal puberty

The aim of this study was to investigate the development of bone mineral density (BMD) and bone mineral content (BMC) in relation to peak height velocity (PHV), and to investigate whether late normal puberty was associated with remaining low BMD and BMC in early adulthood in men. In total, 501 men (mean ± SD, 18.9 ± 0.5 years of age at baseline) were included in this 5‐year longitudinal study. Areal BMD (aBMD) and BMC, volumetric BMD (vBMD) and cortical bone size were measured using dual‐energy X‐ray absorptiometry (DXA) and pQCT. Detailed growth and weight charts were used to calculate age at PHV, an objective assessment of pubertal timing. Age at PHV was a strong positive predictor of the increase in aBMD and BMC of the total body (R² aBMD 11.7%; BMC 4.3%), radius (R² aBMD 23.5%; BMC 22.3%), and lumbar spine (R² aBMD 11.9%; BMC 10.5%) between 19 and 24 years (p < 0.001). Subjects were divided into three groups according to age at PHV (early, middle, and late). Men with late puberty gained markedly more in aBMD and BMC at the total body, radius, and lumbar spine, and lost less at the femoral neck (p < 0.001) than men with early puberty. At age 24 years, no significant differences in aBMD or BMC of the lumbar spine, femoral neck, or total body were observed, whereas a deficit of 4.2% in radius aBMD, but not in BMC, was seen for men with late versus early puberty (p < 0.001). pQCT measurements of the radius at follow‐up demonstrated no significant differences in bone size, whereas cortical and trabecular vBMD were 0.7% (p < 0.001) and 4.8% (p < 0.05) lower in men with late versus early puberty. In conclusion, our results demonstrate that late puberty in males was associated with a substantial catch up in aBMD and BMC in young adulthood, leaving no deficits of the lumbar spine, femoral neck, or total body at age 24 years. © 2012 American Society for Bone and Mineral Research.     

Jumping improves hip and lumbar spine bone mass in prepubescent children: a randomized controlled trial.

Physical activity during childhood is advocated as one strategy for enhancing peak bone mass (bone mineral content [BMC]) as a means to reduce osteoporosis-related fractures. Thus, we investigated the effects of high-intensity jumping on hip and lumbar spine bone mass in children. Eighty-nine prepubescent children between the ages of 5.9 and 9.8 years were randomized into a jumping (n = 25 boys and n = 20 girls) or control group (n = 26 boys and n = 18 girls). Both groups participated in the 7-month exercise intervention during the school day three times per week. The jumping group performed 100, two-footed jumps off 61-cm boxes each session, while the control group performed nonimpact stretching exercises. BMC (g), bone area (BA; cm2), and bone mineral density (BMD; g/cm2) of the left proximal femoral neck and lumbar spine (L1-L4) were assessed by dual-energy X-ray absorptiometry (DXA; Hologic QDR/4500-A). Peak ground reaction forces were calculated across 100, two-footed jumps from a 61-cm box. In addition, anthropometric characteristics (height, weight, and body fat), physical activity, and dietary calcium intake were assessed. At baseline there were no differences between groups for anthropometric characteristics, dietary calcium intake, or bone variables. After 7 months, jumpers and controls had similar increases in height, weight, and body fat. Using repeated measures analysis of covariance (ANCOVA; covariates, initial age and bone values, and changes in height and weight) for BMC, the primary outcome variable, jumpers had significantly greater 7-month changes at the femoral neck and lumbar spine than controls (4.5% and 3.1%, respectively). In repeated measures ANCOVA of secondary outcomes (BMD and BA), BMD at the lumbar spine was significantly greater in jumpers than in controls (2.0%) and approached statistical significance at the femoral neck (1.4%; p = 0.085). For BA, jumpers had significantly greater increases at the femoral neck area than controls (2.9%) but were not different at the spine. Our data indicate that jumping at ground reaction forces of eight times body weight is a safe, effective, and simple method of improving bone mass at the hip and spine in children. This program could be easily incorporated into physical education classes.     

Dose Related Association of Impact Activity and Bone Mineral Density in Pre-pubertal Girls

Impact activity is an important contributor to bone accrual. Children engaging in such activity have been shown to have greater bone mineral density (BMD) than their peers. This cross-sectional study was designed to quantify the association between BMD and impact activity in pre-pubescent girls, specifically examining for a dose-dependent relationship. Fifty 7-11-year-old Caucasian female gymnasts were grouped by hours of gymnastics participation during a 6-month period: LOW, 1-8 hours/week (hrs/wk); HIGH, >8 hrs/wk. They were compared with 20 controls, with height, weight, age, and Tanner stage averages matched to the gymnasts. Total body, forearm, hip, lumbar spine BMD, and body composition were measured by dual energy X-ray absorptiometry (DXA). Strength was measured by one repetition maximum testing, calcium intake was quantified by questionnaire, and physical activity was measured by questionnaire and activity monitors. Total and regional BMD were greater in the HIGH group than the controls (P<0.05). Furthermore, both total and forearm BMD were greater in the HIGH group than in the LOW group, and greater in the LOW group than in the controls (P<0.05). Simple regression analysis between hrs/wk of gymnastics activity versus total and regional BMD (using maturation-adjusted Z scores) yielded a positive slope for each site. R2 was greatest for hip BMD (R2 = 0.25), and least for lumbar spine (R2 = 0.10) (P<0.0001). In conclusion, in this group of pre-pubescent girls, we observed a dose-dependent relationship between BMD and hrs/wk of impact activity; even moderate doses of impact activity were associated with increased BMD.     

Maturity and activity-related differences in bone mineral density: Tanner I vs. II and gymnasts vs. non-gymnasts

This study tests the hypotheses that (1) Tanner I and Tanner II girls comprise distinct maturational cohorts, exhibiting BMD differences that are not explained by age and body size alone; and (2) within these distinct maturational cohorts, BMD is higher in gymnasts than non-gymnasts, independent of age and body size. Premenarcheal artistic gymnasts (n=28) and non-gymnasts (n=28) were evaluated. Fan-beam DXA measured areal BMD (aBMD) at the forearm, femoral neck, and lumbar spine; fat free mass (FFM) was derived from whole-body scans. Height, weight, physical activity and calcium intake were assessed. Group means were compared using ANOVA; ANCOVA was used to adjust for age, height and FFM. For all 3 sites and both maturity levels, gymnasts had higher aBMD than non-gymnasts, independent of age and body size (7.2-20.8%, p<0.04). After adjustment for age, height and FFM, Tanner II gymnasts demonstrated lower aBMD than Tanner I gymnasts at the femoral neck (7.6%, p<0.05); no other maturity group comparisons yielded statistically significant differences independent of age and body size. In conclusion, for both Tanner groups, the osteogenic role of impact activity is evident at all three sites. Trends in Tanner group differences in aBMD were specific to gymnast and non-gymnast activity groups and therefore were not generalizable to all subjects. Overall, aBMD correlations and ANCOVA results differ by activity group, maturity level and site. These results highlight the need to consider both maturity and activity status in studies assessing bone accrual.     

Assessment of Bone Density by DXA in Poorly Controlled Children With β-Thalassemia: Correction for Hepatic Iron Overload by Manual Analysis

Introduction: Beta thalassemia major (BTM) is characterized by anemia and iron overload, especially with inadequate chelation therapy. Dual energy x-ray absorptiometry software (DXA) may misanalyse bone measurements due to iron deposition in organs such as the liver. Our objective was to study difference between the posterior-anterior spine measurements of bone mineral content (BMC), area (BA) and density (BMD) in poorly chelated beta thalassemia patients with and without inclusion of the liver in the DXA analysis. Methods: We studied hemoglobin and serum ferritin concentrations in 208 patients with BTM (children n = 177, young adults n = 31). Posteroanterior spine measurements BMC, BA and areal BMD were performed using a GE iDXA. Using the tissue point typing feature (EnCore software, version 16), analysis was carried out including and excluding (manually) the iron overloaded liver. Machine generated Z-scores of L1-L4 BMD were used for analysis. Results: The mean age of the study group was 12.9 ± 5.4 yr. Mean hemoglobin and serum ferritin concentrations were 8.0 ± 1.7 g/dl and 2256.9 ± 1978.0 ng/ml, respectively. The mean BMC, BA, and aBMD at the lumbar spine were 23.2 ± 11.4 g, 29.9 ± 8.5 cm² and 0.736 ± 0.173 g/cm² respectively with inclusion of liver that is standard machine analysis. After the liver was excluded from the analysis, the mean BMC, BA, and aBMD were 23.9 ± 11.6 g, 30.0 ± 8.6 cm² and 0.757 ±0.173 g/cm^2, respectively and the BMC and aBMD were significantly greater (p < 0.05). Mean BMD Z-score was −1.5 ± 1.2, which significantly (p < 0.05) improved to −1.3 ± 1.2 after exclusion of the liver from the analysis. Conclusion: In poorly chelated patients with thalassemia, inclusion of the iron-overloaded liver in the tissue analysis may exaggerate the deficit in bone parameters. Iron overloaded tissues need to be manually excluded during analysis of the PA spine.     

Bone mineral response to a 7-month randomized controlled, school-based jumping intervention in 121 prepubertal boys: associations with ethnicity and body mass index.

We examined the effects of a 7-month jumping intervention (10 minutes, 3 times per week) on bone mineral gain in prepubertal Asian and white boys (10.3+/-0.6 years, 36.0+/-9.2 kg) at 14 schools randomized to control (n = 60) and intervention (n = 61) groups. Intervention and control groups had similar mean baseline and change in height, weight, lean mass and fat mass, baseline areal bone mineral density (aBMD; g/cm2), bone mineral content (BMC; g; dual-energy X-ray absorptiometry [DXA], QDR 4500W), and similar average physical activity and calcium intakes. Over 7 months, the intervention group gained more total body (TB) BMC (1.6%,p < 0.01) and proximal femur (PF) aBMD (1%, p < 0.05) than the control group after adjusting for age, baseline weight, change in height, and loaded physical activity. We also investigated the 41 Asian and 50 white boys (10.2+/-0.6 years and 31.9+/-4.4 kg) who were below the 75th percentile (19.4 kg/m2) of the cohort mean for baseline body mass index (BMI). Boys in the intervention group gained significantly more TB and lumbar spine (LS) BMC, PF aBMD, and trochanteric (TR) aBMD (+ approximately2%) than boys in the control group (adjusted for baseline weight, final Tanner stage, change in height, and loaded physical activity). Bone changes were similar between Asians and whites. Finally, we compared the boys in the control group (n = 16) and the boys in the intervention group (n = 14) whose baseline BMI fell in the highest quartile (10.5+/-0.6 years and 49.1+/-8.2 kg). Seven-month bone changes (adjusted as aforementioned) were similar in the control and intervention groups. In summary, jumping exercise augmented bone mineral accrual at several regions equally in prepubertal Asian and white boys of average or low BMI, and intervention effects on bone mineral were undetectable in high BMI prepubertal boys.     

A Longitudinal Study of Bone Mineral Accrual during Growth in Competitive Premenarcheal Rhythmic Gymnasts

The purpose of this investigation was to study whether prolonged competitive rhythmic gymnastics training influenced bone mineral accrual in premenarcheal girls. Eighty-nine girls (45 rhythmic gymnasts [RG] and 44 untrained controls [UC]) between 7 and 9 years of age were recruited and measured annually for four years (not all participants were measured at every occasion). Dual energy x-ray absorptiometry was used to assess the development of whole body (WB), femoral neck (FN) and lumbar spine (LS) bone mineral content (BMC). In addition, body composition, blood adipokine and jumping performance characteristics were obtained. For longitudinal analyses, hierarchical mixed-effects models were constructed to predict differences in the development of WB, FN and LS BMC between RG and UC groups, while accounting for differences in body composition, blood adipokine and jumping performance values. It appeared that from 8 years of age, RG had lower (p < 0.05) fat mass and leptin values, and higher (p < 0.05) jumping performance measures in comparison with UC girls. Hierarchical mixed-effects models demonstrated that RG had 71.9 ± 12.0, 0.23 ± 0.11 and 1.39 ± 0.42 g more (p < 0.05) WB, FN and LS BMC, respectively, in comparison with UC girls. In addition, WB, FN and LS BMC increased more (p < 0.05) between 7 to 12 years of age in RG girls in comparison with UC. In conclusion, these findings suggest that the prolonged exposure to competitive rhythmic gymnastics trainings in premenarcheal girls is associated with greater bone mineral accrual despite lower body fat mass and leptin values.Key points

• Study examined long-term association between the exposure to competitive rhythmic gymnastics training and bone mineral accrual at the whole body, femoral neck and lumbar spine sites of the skeleton in premenarcheal rhythmic gymnasts.
• Prolonged exposure to competitive rhythmic gymnastics training before menarche provides skeletal benefits to bone mineral accrual at all measured skeletal sites despite lowered body fat mass and leptin values.

Key words: Rhythmic gymnastics, premenarcheal girls, bone mineral content, longitudinal development, adipokines, fat mass     

Dual X-ray absorptiometry (DXA) of the lumbar spine in a clinical paediatric setting: does the method of size-adjustment matter?

Dual X-ray absorptiometry (DXA) is increasingly used in a clinical setting to evaluate bone mass in children. Areal Bone Mineral Density (aBMD) measurements are known to be influenced by body size, but there is no consensus on the optimal way to deal with this for individual patients. AIM: To compare parameters of bone mass with varying degrees of size correction and to determine the effect on the categorisation of patients as normal or abnormal. SUBJECTS AND METHODS: Healthy children (n = 78) and 4 groups of patients (n = 194) underwent DXA scans of the lumbar spine (L2-4, GE Lunar Prodigy). Five measures of bone mass were derived, all adjusted for age and sex: aBMD, BMAD (BMC/BA (1.5)), BMCh (BMC/height3), BMCa (BMC adjusted for BA), BMCt (BMC adjusted for BA and height). SD scores were calculated for each parameter for patients using data from healthy controls. RESULTS: Compared to healthy children, all patient groups had significantly reduced BMD SD scores (P < 0.001). Mean BMAD, BMCa and BMCt SD scores were significantly lower in only 2/4 patient groups, whilst BMCh SD scores were low only in one group. BMCt showed no advantage over BMCa. The proportion of patients with SD scores <-2 was 27% for aBMD but between 10-13% for BMAD, BMCh and BMCa. CONCLUSIONS: All size-corrected parameters of bone mass performed similarly and classified significantly fewer patients as abnormal than did aBMD. The use of one of these parameters should reduce the number of patients diagnosed inappropriately with 'low bone mass'. However, without validation against an outcome measure or 'gold standard' of bone density or structure, it is not possible to determine which parameter is most correct.