Former premenarcheal gymnasts exhibit site‐specific skeletal benefits in adulthood after long‐term retirement

Young female gymnasts have greater bone strength compared to controls; although possibly due to selection into gymnastics, it is thought that their loading activity during growth increases their bone mass, influencing both bone geometry and architecture. If such bone mass and geometric adaptations are maintained, this may potentially decrease the risk of osteoporosis and risk of fracture later in life. However, there is limited evidence of the persisting benefit of gymnastic exercise during growth on adult bone geometric parameters. Therefore, the purpose of this study was to determine whether adult bone geometry, volumetric density, and estimated strength were greater in retired gymnasts compared to controls, 10 years after retirement from the sport. Bone geometric and densitometric parameters, measured by peripheral quantitative computed tomography (pQCT) at the radius and tibia, were compared between 25 retired female gymnasts and 22 controls, age range 22 to 30 years, by multivariate analysis of covariance (covariates: age, height, and muscle cross‐sectional area). Retired gymnasts had significantly greater adjusted total and trabecular area (16%), total and trabecular bone mineral content (BMC) (18% and 22%, respectively), and estimated strength (21%) at the distal radius (p < 0.05) than controls. Adjusted total and cortical area and BMC, medullary area, and estimated strength were also significantly greater (13% to 46%) in retired gymnasts at the 30% and 65% radial shaft sites (p < 0.05). At the distal tibia, retired gymnasts had 12% to 13% greater total and trabecular BMC and volumetric bone mineral density as well as 21% greater estimated strength; total and cortical BMC and estimated strength were also greater at the tibial shaft (8%, 11%, and 10%, respectively) (p < 0.05). Former female gymnasts have significantly better geometric and densitometric properties, as well as estimated strength, at the radius and tibia 10 years after retirement from gymnastics compared to females who did not participate in gymnastics in childhood and adolescence. © 2012 American Society for Bone and Mineral Research.     

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     

Structural Strength Development at the Proximal Femur in 4‐ to 10‐Year‐Old Precompetitive Gymnasts: A 4‐Year Longitudinal Hip Structural Analysis Study

Gymnastics, a high‐impact weight‐bearing physical activity, has been shown to be highly osteogenic. Previously in this cohort, bone mass development (bone mineral content accrual [BMC]) was shown to be positively associated with low‐level (recreational) gymnastics exposure (1 to 2 hours per week); however, BMC is only one single component of bone strength. Bone strength is influenced not only by bone mineralization but also bone geometry, bone architecture, and the imposing loads on the bone. The aim of this study was to investigate whether low‐level gymnastics training influenced the estimated structural geometry development at the proximal femur. A total of 165 children (92 gymnasts and 73 non‐gymnasts) between the ages of 4 and 6 years were recruited into this study and assessed annually for 4 years. During the 4 years, 64 gymnasts withdrew from the sport and were reclassified as ex‐gymnasts. A dual‐energy X‐ray absorptiometry (DXA) image of each child's hip was obtained. Values of cross‐sectional area (CSA), section modulus (Z), and cortical thickness (CT) at the narrow neck (NN), intertrochanter (IT), and shaft (S) were estimated using the hip structural analysis (HSA) program. Multilevel random‐effects models were constructed and used to develop bone structural strength development trajectories (estimate ± SEE). Once the confounders of body size and lifestyle were controlled, it was found that gymnasts had 6% greater NN CSA than non‐gymnasts controls (0.09 ± 0.03 cm², p < 0.05), 7% greater NN Z (0.04 ± 0.01 cm³, p < 0.05), 5% greater IT CSA (0.11 ± 0.04 cm³, p < 0.05), 6% greater IT Z (0.07 ± 0.03 cm³, p < 0.05), and 3% greater S CSA (0.06 ± 0.03 cm³, p < 0.05). These results suggest that early exposure to low‐level gymnastics participation confers benefits related to geometric and bone architecture properties during childhood and, if maintained, may improve bone health in adolescence and adulthood. © 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.     

History of amenorrhoea compromises some of the exercise-induced benefits in cortical and trabecular bone in the peripheral and axial skeleton: A study in retired elite gymnasts

BackgroundFemale gymnasts frequently present with overt signs of hypoestrogenism, such as late menarche or menstrual dysfunction. The objective was to investigate the impact of history of amenorrhoea on the exercise-induced skeletal benefits in bone geometry and volumetric density in retired elite gymnasts.Subjects and methods24 retired artistic gymnasts, aged 17–36 years, who had been training for at least 15 h/week at the peak of their career and had been retired for 3–18 years were recruited. They had not been engaged in more than 2 h/week of regular physical activity since retirement. Former gymnasts who reported history of amenorrhoea (‘AME’, n = 12: either primary or secondary amenorrhoea) were compared with former gymnasts (‘NO-AME’, n = 12) and controls (‘C’, n = 26) who did not report history of amenorrhoea. Bone mineral content (BMC), total bone area (ToA) and total volumetric density (ToD) were measured by pQCT at the radius and tibia (4% and 66%). Trabecular volumetric density (TrD) and bone strength index (BSI) were measured at the 4% sites. Cortical area (CoA), cortical thickness (CoTh), medullary area (MedA), cortical volumetric density (CoD), stress–strain index (SSI) and muscle and fat area were measured at the 66% sites. Spinal BMC, areal BMD and bone mineral apparent density (BMAD) were measured by DXA.ResultsMenarcheal age was delayed in AME when compared to NO-AME (16.4 ± 0.5 years vs. 13.3 ± 0.4 years, p < 0.001). No differences were detected between AME and C for height-adjusted spinal BMC, aBMD and BMAD, TrD and BSI at the distal radius and tibia, CoA at the proximal radius, whereas these parameters were greater in NO-AME than C (p < 0.05–0.005). AME had lower TrD and BSI at the distal radius, and lower spinal BMAD than NO-AME (p < 0.05) but they had greater ToA at the distal radius (p < 0.05).ConclusionGreater spinal BMC, aBMD and BMAD as well as trabecular volumetric density and bone strength in the peripheral skeleton were found in former gymnasts without a history of menstrual dysfunction but not in those who reported either primary or secondary amenorrhoea. History of amenorrhoea may have compromised some of the skeletal benefits associated with high-impact gymnastics training.     

Bone Structure and Volumetric BMD in Overweight Children: A Longitudinal Study

The effect of excess body fat on bone strength accrual is not well understood. Therefore, we assessed bone measures in healthy weight (HW) and overweight (OW) children. Children (9–11 yr) were classified as HW (n = 302) or OW (n = 143) based on body mass index. We assessed total (ToD) and cortical (CoD) volumetric BMD and bone area, estimates of bone strength (bone strength index [BSI]; stress‐strain index [SSIp]), and muscle cross‐sectional area (CSA) at the distal (8%), midshaft (50%), and proximal (66%) tibia by pQCT. We used analysis of covariance to compare bone outcomes at baseline and change over 16 mo. At baseline, all bone measures were significantly greater in OW compared with HW children (+4–15%; p ≤ 0.001), with the exception of CoD at the 50% and 66% sites. Over 16 mo, ToA increased more in the OW children, whereas there was no difference for change in BSI or ToD between groups at the distal tibia. At the tibial midshaft, SSIp was similar between groups at baseline when adjusted for muscle CSA, but low when adjusted for body fat in the OW group. At both sites, bone strength increased more in OW because of a greater increase in bone area. Changes in SSIp were associated with changes in lean mass (r = 0.70, p < 0.001) but not fat mass. In conclusion, although OW children seem to be at an advantage in terms of absolute bone strength, bone strength did not adapt to excess body fat. Rather, bone strength was adapted to the greater muscle area in OW children.     

Muscle Torque Relative to Cross‐Sectional Area and the Functional Muscle‐Bone Unit in Children and Adolescents With Chronic Disease

Measures of muscle mass or size are often used as surrogates of forces acting on bone. However, chronic diseases may be associated with abnormal muscle force relative to muscle size. The muscle‐bone unit was examined in 64 children and adolescents with new‐onset Crohn's disease (CD), 54 with chronic kidney disease (CKD), 51 treated with glucocorticoids for nephrotic syndrome (NS), and 264 healthy controls. Muscle torque was assessed by isometric ankle dynamometry. Calf muscle cross‐sectional area (CSA) and tibia cortical section modulus (Zp) were assessed by quantitative CT. Log‐linear regression was used to determine the relations among muscle CSA, muscle torque, and Zp, adjusted for tibia length, age, Tanner stage, sex, and race. Muscle CSA and muscle torque‐relative‐to‐muscle CSA were significantly lower than controls in advanced CKD (CSA ?8.7%, p = 0.01; torque ?22.9%, p < 0.001) and moderate‐to‐severe CD (CSA ?14.1%, p < 0.001; torque ?7.6%, p = 0.05), but not in NS. Zp was 11.5% lower in advanced CKD (p = 0.005) compared to controls, and this deficit was attenuated to 6.7% (p = 0.05) with adjustment for muscle CSA. With additional adjustment for muscle torque and body weight, Zp was 5.9% lower and the difference with controls was no longer significant (p = 0.09). In participants with moderate‐to‐severe CD, Zp was 6.8% greater than predicted (p = 0.01) given muscle CSA and torque deficits (R² = 0.92), likely due to acute muscle loss in newly‐diagnosed patients. Zp did not differ in NS, compared with controls. In conclusion, muscle torque relative to muscle CSA was significantly lower in CKD and CD, compared with controls, and was independently associated with Zp. Future studies are needed to determine if abnormal muscle strength contributes to progressive bone deficits in chronic disease, independent of muscle area. © 2014 American Society for Bone and Mineral Research.     

Differences in Macro‐ and Microarchitecture of the Appendicular Skeleton in Young Chinese and White Women

To identify the racial differences in macro‐ and microstructure of the distal radius and tibia that may account for the lower fracture rates in Asians than whites, we studied 61 healthy premenopausal Chinese and 111 white women 18–45 yr of age using high‐resolution pQCT (HR‐pQCT). The Chinese were shorter and leaner. Distal radius total cross‐sectional area (CSA) was 14.3% smaller in Chinese because of an 18.0% smaller trabecular area (p < 0.001). Cortical thickness was 8.8% greater in the Chinese, but cortical area was no different. Total volumetric BMD (vBMD) was 10.3% higher in the Chinese because of the 8.8% higher cortical thickness and 2.8% greater cortical density (all p < 0.01). Trabecular vBMD and bone volume/tissue volume (BV/TV) did not differ by race because trabeculae were 7.0% fewer but 10.8% thicker in Chinese than whites (both p < 0.01). Similar results were found at the distal tibia. Lower fracture risk in Chinese women may be partly caused by thicker cortices and trabeculae in a smaller bone‐more bone within the bone than in whites.     

Current Physical Activity Is Independently Associated With Cortical Bone Size and Bone Strength in Elderly Swedish Women

Physical activity is believed to have the greatest effect on the skeleton if exerted early in life, but whether or not possible benefits of physical activity on bone microstructure or geometry remain at old age has not been investigated in women. The aim of this study was to investigate if physical activity during skeletal growth and young adulthood or at old age was associated with cortical geometry and trabecular microarchitecture in weight‐bearing and non–weight‐bearing bone, and areal bone mineral density (aBMD) in elderly women. In this population‐based cross‐sectional study 1013 women, 78.2 ± 1.6 (mean ± SD) years old, were included. Using high‐resolution 3D pQCT (XtremeCT), cortical cross‐sectional area (Ct.CSA), cortical thickness (Ct.Th), cortical periosteal perimeter (Ct.Pm), volumetric cortical bone density (D.Ct), trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) were measured at the distal (14% level) and ultra‐distal tibia and radius, respectively. aBMD was assessed using DXA (Hologic Discovery A) of the spine and hip. A standardized questionnaire was used to collect information about previous exercise and the Physical Activity Scale for the Elderly (PASE) was used for current physical activity. A linear regression model (including levels of exercise during skeletal growth and young adulthood [10 to 30 years of age], PASE score, and covariates) revealed that level of current physical activity was independently associated with Ct.CSA (β = 0.18, p < 0.001) and Ct.Th (β = 0.15, p < 0.001) at the distal tibia, Tb.Th (β = 0.11, p < 0.001) and BV/TV (β = 0.10, p = 0.001) at the ultra‐distal tibia, and total hip aBMD (β = 0.10, p < 0.001). Current physical activity was independently associated with cortical bone size, in terms of thicker cortex but not larger periosteal circumference, and higher bone strength at the distal tibia on elderly women, indicating that physical activity at old age may decrease cortical bone loss in weight‐bearing bone in elderly women. © 2016 American Society for Bone and Mineral Research.     

Percent fat mass is inversely associated with bone mass and hip geometry in rural Chinese adolescents

This study was an attempt to examine the phenotypic, genetic, and environmental correlations between percent fat mass (PFM) and bone parameters, especially hip geometry, among 786 males and 618 females aged 13 to 21 years from a Chinese twin cohort. PFM, bone area (BA), bone mineral content (BMC), cross‐sectional area (CSA), and section modulus (SM) were obtained by dual‐energy X‐ray absorptiometry. Multiple linear regression models were used to assess the PFM‐bone relationships. A structural equation model for twin design was used to estimate genetic/environmental influences on individual phenotype and phenotypic correlations. After controlling for body weight and other pertinent covariates, we observed inverse associations between PFM and bone parameters: Compared with the lowest age‐ and gender‐specific tertile of PFM, males in the highest tertile of PFM had lower measures of whole‐body‐less‐head BA (WB‐BA), lumbar spine BA (L₂–L₄‐BA), total‐hip BA (TH‐BA), total‐hip BMC, CSA, and SM (p < .005 for all, adjusted p < .05). Similar inverse associations were observed in females for all the preceding parameters except WB‐BA and L2–L₄‐BA. These associations did not vary significantly by Tanner stages. In both genders, the estimated heritabilities were 80% to 86% for BMC, 67% to 80% for BA, 74% to 77% for CSA, and 64% for SM. Both shared genetics and environmental factors contributed to the inverse PFM‐bone correlations. We conclude that in this sample of relatively lean Chinese adolescents, at a given body weight, PFM is inversely associated with BA, BMC, and hip geometry in both genders, and such associations are attributed to both shared genetic and environmental factors. © 2010 American Society for Bone and Mineral Research     

Bone geometry and density in the skeleton of pre-pubertal gymnasts and school children

We have studied the differences between the peripheral and axial skeleton of pre-pubertal gymnasts and controls. We hypothesised that compared to controls, gymnasts would have larger and stronger radius and tibia diaphyses with greater bone mineral content and larger cross-sectional muscle area. At the distal metaphyseal sites of the radius and tibia, gymnasts would have greater bone cross-sectional area and total and trabecular volumetric bone mineral density (vBMD). Differences between the lumbar spine, total body and body composition in gymnasts versus controls were also studied. Peripheral quantitative computed tomography (pQCT) was used to measure bone geometry, density and muscle of the peripheral skeleton; dual energy X-ray absorptiometry (DXA) for total body and axial measurements.

Eighty-six pre-pubertal children, 44 gymnasts (mean age 9.0 years, range 5.4–11.9 years) and 42 controls (mean age 8.8 years, range 5.6–11.9 years) were studied. Eighty-four children were Caucasian, one child was mixed race, one Chinese. Data were adjusted for age, sex and height. Differences in the effect size between sexes were also tested.

At the 50% radius diaphysis gymnasts had larger bones (9.2%, p = 0.0054) with greater cortical area (8.2%, p = 0.022) and stress strain index (surrogate measure of bone strength) than controls (13.6%, p = 0.015). The effect size was different between males and females for cortical thickness (p = 0.03). At the 65% tibia diaphysis, gymnasts had greater cortical area (5.3%, p = 0.057) and thickness (6.2%, p = 0.068) than controls; consequently, bone strength was 5.4% higher (p = 0.14). There were no significant differences in cortical volumetric bone mineral density (vBMD) at the radius or tibia diaphysis between the groups. There was a difference in effect size for tibia muscle cross-sectional area between the sexes (p = 0.035). At the distal radius and tibia total and trabecular vBMD was greater (Total: radius 17%, p < 0.0001, tibia: 5.7%, p = 0.0053; trabecular: radius 21%, p < 0.0001, tibia 4.5%, p = 0.11). Bone size was not different in gymnasts compared to controls

Lumbar spine BMC (12.3%, p = 0.0007), areal bone mineral density (aBMD) (9.1%, p = 0.0006) and bone mineral apparent density (BMAD) (7.6%, p = 0.0047) were greater in gymnasts but vertebral size was not significantly different. Likewise, total body BMD (3.5%, p = 0.0057) and BMC (4.78%, p = 0.085) were greater in gymnasts but there were no differences in skeletal size.

These data suggest site-specific differences in how the pre-pubertal skeleton develops in response to the repetitive loading it experiences when participating in regular gymnastics. At diaphyseal sites these differences are predominantly in the bone and muscle geometry and not density. Conversely, at trabecular sites, the differences are increased density rather than geometry.

In conclusion, the present study has demonstrated skeletal differences between gymnasts and controls. These differences appear to be site and sex specific.     

Exercise During Growth and Young Adulthood Is Independently Associated With Cortical Bone Size and Strength in Old Swedish Men

Previous studies have reported an association between exercise during youth and increased areal bone mineral density at old age. The primary aim of this study was to investigate if exercise during growth was independently associated with greater cortical bone size and whole bone strength in weight‐bearing bone in old men. The tibia and radius were measured using both peripheral quantitative computed tomography (pQCT) (XCT‐2000; Stratec) at the diaphysis and high‐resolution pQCT (HR‐pQCT) (XtremeCT; Scanco) at the metaphysis to obtain cortical bone geometry and finite element–derived bone strength in distal tibia and radius, in 597 men, 79.9 ± 3.4 (mean ± SD) years old. A self‐administered questionnaire was used to collect information about previous and current physical activity. In order to determine whether level of exercise during growth and young adulthood or level of current physical activity were independently associated with bone parameters in both tibia and radius, analysis of covariance (ANCOVA) analyses were used. Adjusting for covariates and current physical activity, we found that men in the group with the highest level of exercise early in life (regular exercise at a competitive level) had higher tibial cortical cross‐sectional area (CSA; 6.3%, p < 0.001) and periosteal circumference (PC; 1.6%, p = 0.011) at the diaphysis, and higher estimated bone strength (failure load: 7.5%, p < 0.001; and stiffness: 7.8%, p < 0.001) at the metaphysis than men in the subgroup with the lowest level of exercise during growth and young adulthood. Subjects in the group with the highest level of current physical activity had smaller tibial endosteal circumference (EC; 3.6%, p = 0.012) at the diaphysis than subjects with a lower current physical activity, when adjusting for covariates and level of exercise during growth and young adulthood. These findings indicate that exercise during growth can increase the cortical bone size via periosteal expansion, whereas exercise at old age may decrease endosteal bone loss in weight‐bearing bone in old men. © 2014 American Society for Bone and Mineral Research.     

Motor Competence in Early Childhood Is Positively Associated With Bone Strength in Late Adolescence

The onset of walking in early childhood results in exposure of the lower limb to substantial forces from weight bearing activity that ultimately contribute to adult bone strength. Relationships between gross motor score (GMS), at 18 months and bone outcomes measured at age 17 years were examined in 2327 participants in the Avon Longitudinal Study of Parents and Children (ALSPAC). Higher GMS indicated greater motor competence in weight‐bearing activities. Total hip bone mineral density (BMD) and hip cross‐sectional moment of inertia (CSMI) were assessed from dual‐energy X‐ray absorptiometry (DXA). Bone measures including cortical bone mineral content (BMC), periosteal circumference (PC), cortical thickness (CT), cortical bone area (CBA), cortical BMD (BMD_C) and cross‐sectional moment of inertia (CSMI) were assessed by peripheral quantitative computed tomography (pQCT) at 50% distal‐proximal length. Before adjustment, GMS was associated with hip BMD, CSMI, and tibia BMC, PC, CT, CBA and CSMI (all p < 0.001) but not BMD_C (p > 0.25). Strongest associations (standardized regression coefficients with 95% CI) were between GMS and hip BMD (0.086; 95% CI, 0.067 to 0.105) and tibia BMC (0.105; 95% CI, 0.089 to 0.121). With the exception of hip BMD, larger regression coefficients were observed in males (gender interactions all p < 0.05). Adjustment for lean mass resulted in substantial attenuation of regression coefficients, suggesting associations between impaired motor competence and subsequent bone development are partly mediated by alterations in body composition. In conclusion, impaired motor competence in childhood is associated with lower adolescent bone strength, and may represent a risk factor for subsequent osteoporosis. © 2015 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research (ASBMR).     

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.     

Smoking is associated with impaired bone mass development in young adult men: A 5-year longitudinal study

It has previously been shown that smoking is associated with reduced bone mass and increased fracture risk, but no longitudinal studies have been published investigating altered smoking behavior at the time of bone mass acquisition. The aim of this study was to investigate the development of bone density and geometry according to alterations in smoking behavior in a 5‐year, longitudinal, population‐based study of 833 young men, age 18 to 20 years (baseline). Furthermore, we aimed to examine the cross‐sectional, associations between current smoking and parameters of trabecular microarchitecture of the radius and tibia, using high‐resolution peripheral quantitative computed tomography (HR‐pQCT), in young men aged 23 to 25 years (5‐year follow‐up). Men who had started to smoke since baseline had considerably smaller increases in areal bone mineral density (aBMD) at the total body (mean ± SD, 0.020 ± 0.047 mg/cm² versus 0.043 ± 0.040 mg/cm², p < 0.01) and lumbar spine (0.027 ± 0.062 mg/cm² versus 0.052 ± 0.065 mg/cm², p = 0.04), and substantially greater decreases in aBMD at the total hip (?0.055 ± 0.058 mg/cm² versus ?0.021 ± 0.062 mg/cm², p < 0.01) and femoral neck (?0.077 ± 0.059 mg/cm² versus ?0.042 ± 0.070 mg/cm², p < 0.01) than men who were nonsmokers at both the baseline and follow‐up visits. At the tibia, subjects who had started to smoke had a smaller increment of the cortical cross‐sectional area (CSA) than nonsmokers (8.1 ± 4.3 mm² versus 11.5 ± 8.9 mm², p = 0.03), and a larger decrement of trabecular volumetric BMD (vBMD) than nonsmokers (?13.9 ± 20.5 mg/mm³ versus ?4.1 ± 13.9 mg/mm³, p < 0.001). In the cross‐sectional analysis at follow‐up (23–25 years of age), smokers had significantly lower trabecular vBMD at the tibia (7.0%, p < 0.01) due to reduced trabecular thickness (8.9%, p < 0.001), as assessed using HR‐pQCT, than nonsmokers. In conclusion, this study is the first to report that men who start to smoke in young adulthood have poorer development of their aBMD at clinically important sites such as the spine and hip than nonsmokers, possibly due to augmented loss of trabecular density and impaired growth of cortical cross‐sectional area. © 2012 American Society for Bone and Mineral Research.     

Previous Sport Activity During Childhood and Adolescence Is Associated With Increased Cortical Bone Size in Young Adult Men

Physical activity during growth has been associated with altered cortical bone geometry, but it remains uncertain if the physical activity–induced increments in cortical bone size remain when the level of physical activity is diminished or ceased. The aim of this study was to investigate if physical activity during growth is associated with cortical bone geometry in currently inactive young men. In this study, 1068 men (18.9 ± 0.6 [SD] yr) were included. Cortical bone geometry at the tibia and radius were measured using pQCT. A standardized questionnaire was used to collect information about current and previous sport activity. Subjects who continued to be active (n = 678) and who had been previously active (n = 285) in sports had a wider cortical bone (periosteal circumference [PC], 4.5% and 3.2%, respectively) with increased cross‐sectional area (CSA; 12.5% and 6.9%) of the tibia than the always inactive subjects (n = 82). In the currently inactive men (n = 367), regression analysis (including covariates age, height, weight, calcium intake, smoking, and duration of inactivity) showed that previous sport activity was independently associated with cortical bone size of the tibia (CSA and PC). Amount of previous sport activity explained 7.3% of the total variation in cortical CSA. Subjects, who ceased their sport activity for up to 6.5 yr previously, still had greater cortical PC and CSA of the tibia than always inactive subjects. The results from this study indicate that sport activity during growth confers positive effects on bone geometry even though sport activity is ceased.     

Genetic and Environmental Variances of Bone Microarchitecture and Bone Remodeling Markers: A Twin Study

All genetic and environmental factors contributing to differences in bone structure between individuals mediate their effects through the final common cellular pathway of bone modeling and remodeling. We hypothesized that genetic factors account for most of the population variance of cortical and trabecular microstructure, in particular intracortical porosity and medullary size – void volumes (porosity), which establish the internal bone surface areas or interfaces upon which modeling and remodeling deposit or remove bone to configure bone microarchitecture. Microarchitecture of the distal tibia and distal radius and remodeling markers were measured for 95 monozygotic (MZ) and 66 dizygotic (DZ) white female twin pairs aged 40 to 61 years. Images obtained using high‐resolution peripheral quantitative computed tomography were analyzed using StrAx1.0, a nonthreshold‐based software that quantifies cortical matrix and porosity. Genetic and environmental components of variance were estimated under the assumptions of the classic twin model. The data were consistent with the proportion of variance accounted for by genetic factors being: 72% to 81% (standard errors ～18%) for the distal tibial total, cortical, and medullary cross‐sectional area (CSA); 67% and 61% for total cortical porosity, before and after adjusting for total CSA, respectively; 51% for trabecular volumetric bone mineral density (vBMD; all p < 0.001). For the corresponding distal radius traits, genetic factors accounted for 47% to 68% of the variance (all p ≤ 0.001). Cross‐twin cross‐trait correlations between tibial cortical porosity and medullary CSA were higher for MZ (r_MZ = 0.49) than DZ (r_DZ = 0.27) pairs before (p = 0.024), but not after (p = 0.258), adjusting for total CSA. For the remodeling markers, the data were consistent with genetic factors accounting for 55% to 62% of the variance. We infer that middle‐aged women differ in their bone microarchitecture and remodeling markers more because of differences in their genetic factors than differences in their environment. © 2014 American Society for Bone and Mineral Research.     

Rapid growth produces transient cortical weakness: A risk factor for metaphyseal fractures during puberty

Fractures of the distal radius in children have a similar incidence to that found in postmenopausal women but occur more commonly in boys than in girls. Fractures of the distal tibia are uncommon in children and show no sex specificity. About 90% of lengthening of the radius but only 30% of lengthening of the tibia during puberty occur at the distal growth plate. We speculated that more rapid modeling at the distal radial metaphysis results in a greater dissociation between growth and mineral accrual than observed at the distal tibia. We measured the macro‐ and microarchitecture of the distal radial and tibial metaphysis using high‐resolution peripheral quantitative computed tomography in a cross‐sectional study of 69 healthy boys and 60 healthy girls aged from 5 to 18 years. Bone diameters were larger but total volumetric bone mineral density (vBMD) was lower at the distal radius (not at the distal tibia) by 20% in boys and by 15% in girls at Tanner stage III than in children of the same sex at Tanner stage I (both p < .05). In boys at Tanner stage III, total vBMD was lower because the larger radial total cross‐sectional area (CSA) had a thinner cortex with lower vBMD than in boys at Tanner stage I. In girls at Tanner stage III, the larger total radial CSA was not associated with a difference in cortical thickness or cortical vBMD relative to girls in Tanner stage I. Cortical thickness and density at both sites in both sexes after Tanner stage III were greater than in younger children. Trabecular bone volume fraction (BV/TV) was higher in boys than in girls at both sites and more so after puberty because trabeculae were thicker in more mature boys but not in girls. There was no sex‐ or age‐related differences in trabecular number at either site. We infer that longitudinal growth outpaces mineral accrual in both sexes at the distal radius, where bone grows rapidly. The dissociation produces transitory low cortical thickness and vBMD in boys but not in girls. These structural features in part may account for the site and sex specificity of metaphyseal fractures during growth. © 2010 American Society for Bone and Mineral Research     

Long-term recreational gymnastics, estrogen use, and selected risk factors for osteoporotic fractures.

The purpose of this cross-sectional study was to examine whether long-term participation in recreational gymnastics or folk dancing or estrogen replacement therapy (ERT) is associated with mechanically more competent bones and improved muscular strength and body balance. One hundred and seventeen healthy, female postmenopausal recreational gymnasts (mean age 62.1 [SD 4.7] years) and 116 sedentary controls (mean age 61.5 [4.6] years) were enrolled in the study. Bone mineral content (BMC) of the distal radius, femoral neck, and trochanter were measured with dual-energy X-ray absorptiometry. BMC of the midshaft and distal tibia and trabecular density (TrD) of the distal tibia were measured with peripheral computed quantitative tomography. Maximal isometric strength, muscular power, cardiorespiratory fitness, and body balance of the participants were also assessed. The cardiorespiratory fitness, muscular strength, and dynamic balance of the recreational gymnasts and folk dancers combined were significantly better than those of the controls, the average group difference ranging from 7.5% (95% confidence interval 5.0-9.9%) in dynamic balance to 12.8% (6.6-19. 4%) in dynamic muscular power. ERT was not associated with the fitness indicators, muscular power, or balance, but was significantly associated with the BMC at all the measured bone sites, the mean group difference between estrogen users and nonusers ranging from 6.5% (3.7-9.3%) for the tibial shaft to 11.8% (6.4-17. 0%) for the distal radius. Recreational gymnastics, in turn, was significantly associated with higher BMC at the tibia only, the mean group difference being 3.9% (0.9-6.9%) for the tibial shaft and 7.7% (3.7-11.9%) for the distal tibia. Recreational gymnastics was also associated with higher TrD at the distal tibia (5.2%; 1.2-9.2%), whereas estrogen usage did not show such association. The results indicate that ERT seems especially effective in preventing postmenopausal bone loss, whereas recreational gymnastics and folk dancing improve muscular performance and body balance in addition to increased bone mass and bone size in the tibia. All these factors are essential in prevention of fall-related fractures of the elderly.     

Effects of a Specialist‐Led,School Physical Education Program on Bone Mass,Structure, and Strength in Primary School Children: A 4‐Year Cluster Randomized Controlled Trial

This 4‐year cluster randomized controlled trial of 365 boys and 362 girls (mean age 8.1 ± 0.3 years) from grade 2 in 29 primary schools investigated the effects of a specialist‐taught physical education (PE) program on bone strength and body composition. All children received 150 min/week of common practice (CP) PE from general classroom teachers but in 13 schools 100 min/week of CP PE was replaced by specialized‐led PE (SPE) by teachers who emphasized more vigorous exercise/games combined with static and dynamic postural activities involving muscle strength. Outcome measures assessed in grades 2, 4, and 6 included: total body bone mineral content (BMC), lean mass (LM), and fat mass (FM) by DXA, and radius and tibia (4% and 66% sites) bone structure, volumetric density and strength, and muscle cross‐sectional area (CSA) by pQCT. After 4‐years, gains in total body BMC, FM, and muscle CSA were similar between the groups in both sexes, but girls in the SPE group experienced a greater gain in total body LM (mean 1.0 kg; 95% CI, 0.2 to 1.9 kg). Compared to CP, girls in the SPE group also had greater gains in cortical area (CoA) and cortical thickness (CoTh) at the mid‐tibia (CoA, 5.0% [95% CI, 0.2% to 1.9%]; CoTh, 7.5% [95% CI, 2.4% to 12.6%]) and mid‐radius (CoA, 9.3% [95% CI, 3.5% to 15.1%]; CoTh, 14.4% [95% CI, 6.1% to 22.7%]), whereas SPE boys had a 5.2% (95% CI, 0.4% to 10.0%) greater gain in mid‐tibia CoTh. These benefits were due to reduced endocortical expansion. There were no significant benefits of SPE on total bone area, cortical density or bone strength at the mid‐shaft sites, nor any appreciable effects at the distal skeletal sites. This study indicates that a specialist‐led school‐based PE program improves cortical bone structure, due to reduced endocortical expansion. This finding challenges the notion that periosteal apposition is the predominant response of bone to loading during the prepubertal and early‐pubertal period. © 2015 American Society for Bone and Mineral Research.