Tomographical description of tennis-loaded radius: reciprocal relation between bone size and volumetric BMD

Inter-arm bone mass and size asymmetries in children tennis players are maturity status specific: a 9-month study on the effects of training time across pubertal change and somatic growth

PURPOSE

Bone growth with exercise is best assessed by tennis-induced inter-arm asymmetries. Yet, the effects of training and maturation across puberty were unclear. This study explored arm bone growth across 9 months of training in 46 tennis players 7-14 years (25 boys, 21 girls).

METHODS

Bone mineral content (BMC) and bone area (BA) were measured from DXA scans. Pubertal status was assessed by Tanner stage (TS) and somatic growth by maturity offset (MO). Children were grouped as pre- (TS I-I), early (TS I-II), and mid/late pubertal (TS II-III).

RESULTS

Training time (TT) change in the three groups was 160-170, 190-230, and 200-220 h, respectively. Bone asymmetries were large in all groups (d > 0.8, P < 0.001): 5-18 g (9-21%) and 9-17 g (17-23%) in girls and boys, respectively, for BMC, and 5-15 cm2 (6-13%) and 9-15 cm2 (12-15%) in girls and boys (10-13%), respectively, for BA. BMC and BA change asymmetry peaked at pre-puberty in girls (56%, 46%) and at early puberty in boys (57%, 43%). Asymmetry gains varied with baseline asymmetry (41%) and change in TT (38%) and TS (17%) in BMC, and with baseline asymmetry (58%) and change in MO (17%) and TS (12%) in BA.

CONCLUSION

All bone asymmetries were substantial. Tennis-induced bone gains were higher at pre- to early puberty in girls and at early to mid/late puberty in boys. Training enhanced mostly bone mass and maturity status enhanced mostly bone size; sex was not bone-change modeling impactful. Implications are discussed considering certain limitations.

Bone Microarchitecture and Strength Adaptation to Physical Activity: A Within-Subject Controlled HRpQCT Study

PURPOSE

Physical activity benefits bone mass and cortical bone size. The current study assessed the impact of chronic (≥10 yr) physical activity on trabecular microarchitectural properties and microfinite element analyses of estimated bone strength.

METHODS

Female collegiate-level tennis players (n = 15; age = 20.3 ± 0.9 yr) were used as a within-subject controlled model of chronic unilateral upper-extremity physical activity. Racquet-to-nonracquet arm differences at the distal radius and radial diaphysis were assessed using high-resolution peripheral quantitative computed tomography. The distal tibia and the tibial diaphysis in both legs were also assessed, and cross-country runners (n = 15; age = 20.8 ± 1.2 yr) included as controls.

RESULTS

The distal radius of the racquet arm had 11.8% (95% confidence interval [CI] = 7.9% to 15.7%) greater trabecular bone volume/tissue volume, with trabeculae that were greater in number, thickness, connectivity, and proximity to each other than that in the nonracquet arm (all P < 0.01). Combined with enhanced cortical bone properties, the microarchitectural advantages at the distal radius contributed a 18.7% (95% CI = 13.0% to 24.4%) racquet-to-nonracquet arm difference in predicted load before failure. At the radial diaphysis, predicted load to failure was 9.6% (95% CI = 6.7% to 12.6%) greater in the racquet versus nonracquet arm. There were fewer and smaller side-to-side differences at the distal tibia; however, the tibial diaphysis in the leg opposite the racquet arm was larger with a thicker cortex and had 4.4% (95% CI = 1.7% to 7.1%) greater strength than the contralateral leg.

CONCLUSION

Chronically elevated physical activity enhances trabecular microarchitecture and microfinite element estimated strength, furthering observations from short-term longitudinal studies. The data also demonstrate that tennis players exhibit crossed symmetry wherein the leg opposite the racquet arm possesses enhanced tibial properties compared with in the contralateral leg.

Skeletal Health and Associated Injury Risk in Collegiate Female Rowers

Baker, BS, Buchanan, SR, and Bemben, DA. Skeletal health and associated injury risk in collegiate female rowers. J Strength Cond Res XX(X): 000-000, 2020-Rowing has been associated with low bone mass and stress fractures. The aim of this study was to compare bone density, geometry, and skeletal asymmetries between competitive female rowers and matched controls and within rowers based on reported injury status, allowing for the calculation of practical injury risk prediction equations. Rowers (n = 24) and controls (n = 24) completed total body, lumbar spine, and and dual femur and radii dual energy x-ray absorptiometry and peripheral quantitative computed tomography scans. One-way analyses of covariance were performed between rowers and controls, and one-way analyses of variance were performed between rowers based on reported rib injury status (injured [n = 11]; injury-free [n = 13]). Logistic regression was used to create prediction models of rowers' injury status. Significance was set at p ≤ 0.05. Rowers were taller, had greater lean mass, less fat mass, and mostly equivalent skeletal measures compared to controls, which were within normal ranges (p < 0.048). Injury-free rowers consumed over 500 mg·d more calcium and were less symmetrical at the 4% tibiae and hips (p < 0.015). The strongest predictive regression model of reported rib injury in rowers comprised calcium intake and the symmetry index of hip strength index (R = 0.833; p < 0.001). A more practical model including daily calcium intake and total bone specific physical activity (PA) scores can be used to correctly predict injury status 75% of the time (R = 0.750; p = 0.022). This is the first study to provide practitioners an injury prediction model for competitive rowers, reiterating the importance of proper nutrition and auxiliary PA focusing on balanced movement patterns.

Study of human radius construction systematics: evaluation by DXA in dry bone

This study has been undertaken in order to describe the bone mass distribution of the dry human radius via dual x-ray absorptiometry (DXA) with a Norland XR-800 densitometer machine. A sample of 39 dry radius bones was used. Two projections were made: antero-posterior and lateral, and five regions of interest were selected. The bone densities and the bone mineral contents of the various regions of the radius in the two projections were compared using Student's t tests for paired samples, with statistically significant differences being found in all of the values, except in the proximal extremity (P Ext). The area of greatest bone mineral content (BMC) was the medial diaphysis (M Diaph), followed by the distal extremity (D Ext), with the lowest value being found in the proximal extremity (P Ext). As for bone mineral density (BMD), a great symmetry is observed if we take the mean point of the longitudinal axis as a reference, with it being distributed from highest to lowest from the central part to the extremities. A correlation study of the BMD and BMC values between the segments themselves and with the total, in both positions, provides us with a high correlation (p ≤ 0.01), with the highest correlation value being found for the proximal diaphysis (P Diaph) region, indicating the heterogeneous nature of the distribution of the radius bone mass. Bone densitometry via DXA is useful in order to establish an overview of the structural construction of the human radius.

Longitudinal effects of swimming on bone in adolescents: a pQCT and DXA study

The aims of the present study were, firstly, to evaluate areal bone mineral density (aBMD), bone strength and structure during a swimming season and compare them to those of normo-active controls (CG), and secondly to ascertain whether practising an additional weight-bearing sport other than swimming might improve bone. Twenty-three swimmers who only swam (SWI-PURE; 14 males, 9 females), 11 swimmers who combined swimming with an additional weight-bearing sport (SWI-SPORT; 8 males, 3 females) and 28 controls (CG; 16 males, 12 females) participated in the present study. aBMD was assessed with dual energy X-ray (DXA). Bone mass, area, structure and strength of the non-dominant tibia and radius were measured with peripheral quantitative computed tomography (pQCT). Measurements were performed at the beginning of the swimming season and 8 months later. The only difference among groups for DXA and pQCT variables was found for arm aBMD, which was higher in the SWI-SPORT than in the CG group at both pre- and post-evaluation. Group by time interactions (GxT) were found for trochanter aBMD when comparing SWI-SPORT to CG and SWI-SPORT to SWI-PURE, favouring in both cases SWI-SPORT. No GxT were found for the radius. For the tibia, GxT were found between SWI-SPORT and CG and between SWI-PURE and CG, in both cases favouring the swimmers. A season of swimming does not confer any additional benefits to aBMD, but may confer minor benefits to structure and mass. Complementing swimming with a weight-bearing activity is beneficial to bone.

Neonatal leptin treatment reverses the bone-suppressive effects of maternal undernutrition in adult rat offspring

Alterations in the early life environment, including maternal undernutrition (UN) during pregnancy, can lead to increased risk of metabolic and cardiovascular disorders in offspring. Leptin treatment of neonates born to UN rats reverses the programmed metabolic phenotype, but the possible benefits of this treatment on bone tissue have not been defined. We describe for the first time the effects of neonatal leptin treatment on bone in adult offspring following maternal UN. Offspring from either UN or ad libitum-fed (AD) rats were treated with either saline or leptin (2.5 µg/ g.d on postnatal days (D)3–13) and were fed either a chow or high fat (HF) diet from weaning until study completion at D170. Analysis of micro-tomographic data of the left femur showed highly significant effects of UN on cortical and trabecular bone tissue indices, contributing to inferior microstructure and bone strength, almost all of which were reversed by early leptin life treatment. The HF fat diet negatively affected trabecular bone tissue, but the effects of only trabecular separation and number were reversed by leptin treatment. The negative effects of maternal UN on skeletal health in adult offspring might be prevented or attenuated by various interventions including leptin. Establishment of a minimal efficacious leptin dose warrants further study.

Calculation of muscle forces during normal gait under consideration of femoral bending moments

This paper introduces a new approach for computing lower extremity muscle forces by incorporating equations that consider "bone structure" and "prevention of bending by load reduction" into existing optimization algorithms. Lower extremity muscle and joint forces, during normal gait, were calculated and compared using two different optimization approaches. We added constraint equations that prevent femoral bending loads to an existing approach that considers "minimal total muscular force". Gait parameters such as kinematics, ground reaction forces, and surface electromyographic activation patterns were examined using standardized gait analysis. A subject-specific anatomic model of the lower extremities, obtained from magnetic resonance images of a healthy male, was used for the simulations. Finite element analysis was used to calculate femoral loads. The conventional method of calculating muscle forces leads to higher rates of femoral bending and structural stress than the new approach. Adding equations with structural subject-specific parameters in our new approach resulted in reduced femoral stress patterns. These findings show that our new approach improves the accuracy of femoral stress and strain simulations. Structural overloads caused by bending can be avoided during inverse calculation of muscle forces.

Bone structure of adolescent swimmers; a peripheral quantitative computed tomography (pQCT) study

OBJECTIVES

The aims of the present study were: (1) to characterize vBMD, bone structure and strength with peripheral quantitative computerized tomography (pQCT) in adolescent swimmers and compare it to normo-active controls (CG); and (2) to evaluate the possible interaction that weight-bearing sports might have on swimmers bone.

DESIGN

Cross-sectional.

METHODS

The non-dominant radius and tibia of 79 (32 females) swimmers and 49 (22 females) CG (both 11-18 years old) were evaluated at proximal and distal sites with a pQCT scanner. Values of total, trabecular and cortical volumetric bone mineral density (vBMD) were obtained from each scan. Cortical thickness, endosteal and periosteal circumferences were also measured and bone strength indexes were calculated. Analyses of covariance were used to compare variables between groups adjusting for age, tanner stage and bone length. Three different analyses were performed according to present and past sport participation in addition to swimming in order to determine differences among swimmers who had performed or were performing other sports (OTHER-SP) (10 females/17 males) and swimmers who had not performed other sports (NO-OTHER-SP) (22 females/22 males). Both of these groups were compared to each other and to a CG (22 females/27 males).

RESULTS

No differences were found between swimmers and CG for bone strength indexes, structure or vBMD (independently of the compared sample).

CONCLUSIONS

These results indicate that swimmers present similar bone strength and structure than CG who did not present high physical activity levels.

Effects of age and starting age upon side asymmetry in the arms of veteran tennis players: a cross-sectional study

While tennis playing results in large bone strength benefits in the racquet arm of young players, the effects of tennis playing in old players have not been investigated. Large side asymmetries in bone strength were found in veteran players, which were more pronounced in men, younger players and childhood starters.

INTRODUCTION

Regular tennis results in large racquet arm bone and muscle strength advantages; however, these effects have not been studied in old players. The non-racquet arm can act as an internal control for the exercising racquet arm without confounding factors, e.g. genotype. Therefore, veteran tennis player side asymmetries were examined to investigate age, sex and starting age effects on bone exercise benefits.

METHODS

Peripheral quantitative computed tomography (pQCT) scans were taken at the radius, ulna and humerus mid-shaft and distal radius in both arms of 88 tennis players (51 males, 37 females; mean age 63.8 ± 11.8 years). Thirty-two players began playing in adulthood, thereby termed 'old starters'; players were otherwise termed 'young starters'.

RESULTS

Muscle size and bone strength were greater in the racquet arm; notably, distal radius bone mineral content (BMC) was 13 ± 10% higher and humeral bone area 23 ± 12% larger (both P < 0.001). Epiphyseal BMC asymmetry was not affected by age (P = 0.863) or sex (P = 0.954), but diaphyseal asymmetries were less pronounced in older players and women, particularly in the humerus where BMC, area and moment of resistance asymmetries were 28-34 % less in women (P < 0.01). Bone area and periosteal circumference asymmetries were smaller in old starters (all P < 0.01); most notably, no distal radius asymmetry was found in this group (0.4 ± 3.4%).

CONCLUSIONS

Tennis participation is associated with large side asymmetries in muscle and bone strength in old age. Larger relative side asymmetries in men, younger players and young starters suggest a greater potential for exercise benefits to bone in these groups.

Is bone tissue really affected by swimming? A systematic review

Background

Swimming, a sport practiced in hypogravity, has sometimes been associated with decreased bone mass.

Aim

This systematic review aims to summarize and update present knowledge about the effects of swimming on bone mass, structure and metabolism in order to ascertain the effects of this sport on bone tissue.

Methods

A literature search was conducted up to April 2013. A total of 64 studies focusing on swimmers bone mass, structure and metabolism met the inclusion criteria and were included in the review.

Results

It has been generally observed that swimmers present lower bone mineral density than athletes who practise high impact sports and similar values when compared to sedentary controls. However, swimmers have a higher bone turnover than controls resulting in a different structure which in turn results in higher resistance to fracture indexes. Nevertheless, swimming may become highly beneficial regarding bone mass in later stages of life.

Conclusion

Swimming does not seem to negatively affect bone mass, although it may not be one of the best sports to be practised in order to increase this parameter, due to the hypogravity and lack of impact characteristic of this sport. Most of the studies included in this review showed similar bone mineral density values in swimmers and sedentary controls. However, swimmers present a higher bone turnover than sedentary controls that may result in a stronger structure and consequently in a stronger bone.

The Lichfield bone study: the skeletal response to exercise in healthy young men

The skeletal response to short-term exercise training remains poorly described. We thus studied the lower limb skeletal response of 723 Caucasian male army recruits to a 12-wk training regime. Femoral bone volume was assessed using magnetic resonance imaging, bone ultrastructure by quantitative ultrasound (QUS), and bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA) of the hip. Left hip BMD increased with training (mean ± SD: 0.85 ± 3.24, 2.93 ± 4.85, and 1.89 ± 2.85% for femoral neck, Ward's area, and total hip, respectively; all P < 0.001). Left calcaneal broadband ultrasound attenuation rose 3.57 ± 0.5% (P < 0.001), and left and right femoral cortical volume by 1.09 ± 4.05 and 0.71 ± 4.05%, respectively (P = 0.0001 and 0.003), largely through the rise in periosteal volume (0.78 ± 3.14 and 0.59 ± 2.58% for right and left, respectively, P < 0.001) with endosteal volumes unchanged. Before training, DXA and QUS measures were independent of limb dominance. However, the dominant femur had higher periosteal (25,991.49 vs. 2,5572 mm(3), P < 0.001), endosteal (6,063.33 vs. 5,983.12 mm(3), P = 0.001), and cortical volumes (19,928 vs. 19,589.56 mm(3), P = 0.001). Changes in DXA, QUS, and magnetic resonance imaging measures were independent of limb dominance. We show, for the first time, that short-term exercise training in young men is associated not only with a rise in human femoral BMD, but also in femoral bone volume, the latter largely through a periosteal response.

The effect of previous conditioning exercise on diaphyseal and metaphyseal bone to imposition and withdrawal of training in young Thoroughbred horses

This study recorded the response to training of the diaphysis of the proximal phalangeal bone and the third metacarpal bone (Mc3) and the Mc3 proximal metaphysis. Nineteen 2- and 3-year old horses in training were exposed either to spontaneous exercise at pasture (PASTEX group) or additional imposed exercise (CONDEX group) from a very young age. Quantitative computed tomography scans were analysed for bone mineral content, size, bone mineral density, periosteal and endosteal circumference, cortical thickness and an estimate of bone strength. The bones of the CONDEX horses were bigger and stronger than those of the PASTEX horses at the start of the observation period, and these differences were maintained after adjusting for training workload. Increase in the bone strength index was through size and not density increase. Density increased during training and decreased during paddock rest between the two training campaigns, during which time bone strength continued to increase because of the slow growth that was still occurring. The greatest variance in the response to the training exercise of diaphyseal bone mineral content, bone strength index or cortical thickness was associated with the cumulative workload index at the gallop, although statistically significant unexplained variances remained. There were no differences in bone response to training, with the exception of the endosteal circumference at 55% of the Mc3 length from the carpometacarpal joint space between CONDEX and PASTEX, which indicated that young horses may be able to be exercised slightly more vigorously than currently accepted.

Effects of repetitive loading on the growth-induced changes in bone mass and cortical bone geometry: a 12-month study in pre/peri- and postmenarcheal tennis players

Pre- and early puberty may be the most opportune time to strengthen the female skeleton, but there are few longitudinal data to support this claim. Competitive female premenarcheal (pre/peri, n = 13) and postmenarcheal (post, n = 32) tennis players aged 10 to 17 years were followed over 12 months. The osteogenic response to loading was studied by comparing the playing and nonplaying humeri for dual-energy X-ray absorptiometry (DXA) bone mineral content (BMC) and magnetic resonance imaging (MRI) total bone area (ToA), medullary area (MedA), cortical area (CoA), and muscle area (MCSA) at the humerus. Over 12 months, growth-induced gains (nonplaying arm) in BMC, ToA, and CoA were greater in pre/peri (10% to 19%, p < .001) than in post (3% to 5%, p < .05 to .001) players. At baseline, BMC, ToA, CoA, and MCSA were 8% to 18% greater in the playing versus nonplaying arms in pre/peri and post players (all p < .001); MedA was smaller in the playing versus nonplaying arms in post only players (p < .05). When comparing the annual gains in the playing arm relative to changes in the nonplaying arm, the increases in ToA and CoA were greater in pre/peri than post players (all p < .05). The smaller the side-to-side differences in BMC and CoA at baseline, the larger the exercise benefits at 12 months (r = -0.39 to -0.48, p < .01). The exercise-induced change in MCSA was predictive of the exercise benefits in BMC in pre/peri players only (p < .05). In conclusion, both pre/peri- and postmenarcheal tennis players showed significant exercise-induced skeletal benefits within a year, with greater benefits in cortical bone geometry in pre/perimenarcheal girls.

Distal radius geometry and skeletal strength indices after peripubertal artistic gymnastics

Development of optimal skeletal strength should decrease adult bone fragility. Nongymnasts (NON): were compared with girls exposed to gymnastics during growth (EX/GYM: ), using peripheral quantitative computed tomography (pQCT) to evaluate postmenarcheal bone geometry, density, and strength. Pre- and perimenarcheal gymnastic loading yields advantages in indices of postmenarcheal bone geometry and skeletal strength.

INTRODUCTION

Two prior studies using pQCT have reported bone density and size advantages in Tanner I/II gymnasts, but none describe gymnasts' bone properties later in adolescence. The current study used pQCT to evaluate whether girls exposed to gymnastics during late childhood growth and perimenarcheal growth exhibited greater indices of distal radius geometry, density, and skeletal strength.

METHODS

Postmenarcheal subjects underwent 4% and 33% distal radius pQCT scans, yielding: 1) vBMD and cross-sectional areas (CSA) (total bone, compartments); 2) polar strength-strain index; 3) index of structural strength in axial compression. Output was compared for EX/GYM: vs. NON: , adjusting for gynecological age and stature (maturity and body size), reporting means, standard errors, and significance.

RESULTS

Sixteen postmenarcheal EX/GYM: (age 16.7 years; gynecological age 3.4 years) and 13 NON: (age 16.2 years; gynecological age 3.6 years) were evaluated. At both diaphysis and metaphysis, EX/GYM: exhibited greater CSA and bone strength indices than NON; EX/GYM: exhibited 79% larger intramedullary CSA than NON: (p < 0.05). EX/GYM: had significantly higher 4% trabecular vBMD; differences were not detected for 4% total vBMD and 33% cortical vBMD.

CONCLUSIONS

Following pre-/perimenarcheal gymnastic exposure, relative to nongymnasts, postmenarcheal EX/GYM: demonstrated greater indices of distal radius geometry and skeletal strength (metaphysis and diaphysis) with greater metaphyseal trabecular vBMD; larger intramedullary cavity size was particularly striking.

Mild exercise early in life produces changes in bone size and strength but not density in proximal phalangeal, third metacarpal and third carpal bones of foals

Exercise or lack of it in early life affects chondro-osseous development. Two groups of horses were used to investigate the effects of age and exercise regimen on bone parameters of diaphyseal, metaphyseal, epiphyseal and cuboidal bones of the distal limb of Thoroughbreds. One group had exercised only spontaneously from an early age at pasture (PASTEX group), while the other group of horses were exposed to a 30% greater workload through additional defined exercise (CONDEX). Longitudinal data from peripheral quantitative computed tomography (pQCT) were obtained from eight scan sites of the left forelimb (proximal phalangeal (P(p); 1 site), third metacarpal (Mc3; six sites) and third carpal (C(3); one site) bones) of 32 Thoroughbred foals scanned five times from ∼3 weeks to 17 months of age. The primary outcome measures were bone mineral content (BMC), bone area (BA), and periosteal circumference (Peri C) in diaphyseal bone, with cortical thickness (CortTh), volumetric bone mineral density (BMD(v)) and a bone strength index (SSI) also being analysed. At the P(p) site within the model there was a significant effect (P=0.00-0.025) of conditioning exercise increasing bone parameters, except endosteal circumference (Endo C) and BMD(v). The BMC, BA, and SSI of P(p) were significantly greater in the CONDEX than PASTEX groups at 12 and 17 months (P=0.015-0.042) and CortTh at 17 months (P=0.033). At the M55 site of Mc3 BMC, BA and SSI (P=0.02-0.04), and at the M33 site, SSI (P=0.05) were higher in the CONDEX than PASTEX group. The adaptive responses, consistent with diaphyseal strengthening, were more marked in the diaphysis of P(p) than Mc3. In the Mc3, metaphysis, trabecular BMD(v) was less in the CONDEX than PASTEX group, associated with greater bone mineral accretion in the outer cortical-sub-cortical bone in the CONDEX group. There were no significant between-group differences in any epiphyseal or cuboidal bone parameter. Although the early imposed exercise regimen was not intensive, it had significant effects on diaphyseal bone strength, through change in size but not bone density.

Upper limb bone mineral density and body composition measured by peripheral quantitative computed tomography in right-handed adults: the role of the dominance effect

BACKGROUND

To investigate the impact on bone and muscle of pathological conditions involving only one of the upper limbs, it is important to know the physiological differences due to the dominance effect.

AIM

To evaluate any physiological differences between dominant and non-dominant upper limbs in terms of bone mineral density (BMD), muscle mass, and muscle density at different levels.

SUBJECTS AND METHODS

The study considered 60 right-handed healthy adults, 30 men and 30 women. Cortical BMD, muscle area, and muscle density were investigated by pQCT-XCT-3000 Stratec at the proximal radius, trabecular and total BMD at the distal radius, and trabecular and cortical BMD at the second phalanx of the third finger. Hand grip strength was also measured.

RESULTS

No significant differences in BMD were found between the dominant and non-dominant upper limbs at any of the sites considered, in men or women. Muscle density was also similar on the two sides, whereas muscle area at the proximal radius was significantly lower on the non-dominant side in both men [4177.5+/-475.1 vs 4009.3+/-552.7 mm2; Delta%: 4.1%; 95% confidence interval (CI) 1.7%-6.5%] and women (2903.9+/-470.9 vs 2720.3+/-411.7 mm2; Delta%: 6.1%; 95%CI 4.3%-7.9%). Hand grip strength proved greater on the right side in both men (48.5+/-8.8 vs 45.2+/-8.7 kg; Delta% 7.1; p<0.001) and women (29.1+/-4.3 vs 27.0+/-5.1 kg; Delta% 7.1; p<0.001).

CONCLUSION

The dominance effect does not seem to influence trabecular or cortical BMD at any of the sites in the upper limb. Muscle density is not modified by dominance, while muscle area is reduced on the non-dominant side and this should be borne in mind when the effect of pathological conditions on the body composition of a single forearm is investigated.

Cross-sectional analysis of long bones, occupational activities and long-distance trade of the Classic Maya from Xcambó--archaeological and osteological evidence

Xcambó is a Classic period Maya site (250-700 AD) situated on the northern coast of Yucatan, Mexico. Archaeological evidence suggests that the site began as a salt production center but adopted a more administrative role as a commercial port in the Late Classic period. Economic growth, depending on its magnitude, could have affected the daily occupations of Xcambó's inhabitants. However, this is difficult to infer from the archaeological record. The aim of this study was to directly evaluate this possibility through skeletal analysis. Since diaphyseal robusticity and shape are predominantly influenced by mechanical loading history, long bone cross-sections can be used to access activity patterns. To this end, humeri and femora of 47 male and 35 female adult specimens from two Xcambó population samples were scrutinized. Our analysis satisfies general archaeological expectations and provides additional information on the population's physical response to economic growth. Decreasing robusticity and femoral anterior-posterior rigidity indicate an overall decrease in physical workload and mobility, concomitant with the site's increasing administrative function. We also observed a significant decrease in sexual dimorphism, possibly attributable to the differential response of male and female physical work spheres during socioeconomic change. In general, our findings suggest even nonsubsistence based socioeconomic change can significantly affect the bone structure of a population, rendering activity analysis an important aspect of the reconstruction of living conditions of past populations.

Improved peripheral cortical bone geometry after surgical treatment of primary hyperparathyroidism in postmenopausal women

CONTEXT

Cortical bone geometry is one of the most important components of bone strength. Excess endogenous PTH or intermittent PTH administration affects cortical bone geometry; however, the changes in cortical bone geometry in patients with primary hyperparathyroidism (pHPT) after parathyroidectomy (PTX) remain unknown.

OBJECTIVE

The present study was performed to examine the longitudinal effects of treating endogenous PTH excess on cortical bone geometry in postmenopausal patients with pHPT by using peripheral quantitative computed tomography.

PATIENTS

Twenty postmenopausal pHPT patients and 30 postmenopausal control subjects matched for age participated in this study.

MAIN OUTCOME MEASURES

Volumetric bone mineral density (vBMD), cortical bone geometric parameters, polar strength strain index, and polar cross-sectional moment of inertia were measured using peripheral quantitative computed tomography at the radius during the year after PTX.

RESULTS

After 1 yr, total and cortical vBMD significantly increased after PTX in the pHPT group (2.9 and 1.6%, respectively), whereas they significantly decreased in the control group (-2.1 and -1.3%, respectively). Significant decreases in cortical thickness and area were observed in the control group (-3.0 and -2.5%, respectively). In contrast, the pHPT group showed increases in cortical thickness and area (8.5 and 7.6%, respectively) as well as polar strength strain index 1 year after PTX.

CONCLUSION

The present longitudinal study showed significant beneficial changes in volumetric BMD, cortical bone geometry, and bone strength index after PTX in postmenopausal women with pHPT.

Health benefits of tennis

The aim of the study was to explore the role of tennis in the promotion of health and prevention of disease. The focus was on risk factors and diseases related to a sedentary lifestyle, including low fitness levels, obesity, hyperlipidaemia, hypertension, diabetes mellitus, cardiovascular disease, and osteoporosis. A literature search was undertaken to retrieve relevant articles. Structured computer searches of PubMed, Embase, and CINAHL were undertaken, along with hand searching of key journals and reference lists to locate relevant studies published up to March 2007. These had to be cohort studies (of either cross sectional or longitudinal design), case-control studies, or experimental studies. Twenty four studies were identified that dealt with physical fitness of tennis players, including 17 on intensity of play and 16 on maximum oxygen uptake; 17 investigated the relation between tennis and (risk factors for) cardiovascular disease; and 22 examined the effect of tennis on bone health. People who choose to play tennis appear to have significant health benefits, including improved aerobic fitness, a lower body fat percentage, a more favourable lipid profile, reduced risk for developing cardiovascular disease, and improved bone health.

Side differences in the bone density of the distal radius and calcaneus in Koreans aged 4-86 years

Although bone mineral density (BMD) measurements of peripheral bone have been widely used due to practical and economic factors, a consensus does not exist as to whether the dominant or nondominant side is preferable for diagnosing osteoporosis and predicting fracture risk. Thus, we evaluated BMD differences of the distal radius and calcaneus between dominant and nondominant sides in the Korean population. Data were collected from 1794 subjects (979 females and 815 males) aged 4-86 yr, who were not taking any medication that affected bone metabolism or had a history of fracture. All subjects completed a questionnaire, and anthropometric and BMD measurements were taken. BMD values at the distal radii and calcanei were measured by dual-energy X-ray absorptiometry using a Lunar instrument. Significant correlations were observed between the dominant and nondominant distal radii (r=0.92; p<0.0001) and calcanei (r=0.94; p<0.0001). A side difference for the distal radius was not observed, whereas a significant side difference for the calcaneus was detected (p<0.05). Our findings provide information for recommending a sampling site upon measuring the distal radius and calcaneus during clinical or community-based studies.

Short-term and long-term site-specific effects of tennis playing on trabecular and cortical bone at the distal radius

Mechanical loading during growth magnifies the normal increase in bone diameter occurring in long bone shafts, but the response to loading in long bone ends remains unclear. The aim of the study was to investigate the effects of tennis playing during growth at the distal radius, comparing the bone response at trabecular and cortical skeletal sites. The influence of training duration was examined by studying bone response in short-term (children) and long-term (young adults) perspectives. Bone area, bone mineral content (BMC), and bone mineral density (BMD) of the radius were measured by DXA in 28 young (11.6 +/- 1.4 years old) and 47 adult tennis players (22.3 +/- 2.7 years old), and 70 age-matched controls (12 children, 58 adults) at three sites: the ultradistal region (trabecular), the mid-distal region, and the third-distal region (cortical). At the ultradistal radius, young and adult tennis players displayed similar side-to-side differences, the asymmetry in BMC reaching 16.3% and 13.8%, respectively (P < 0.0001). At the mid- and third-distal radius, the asymmetry was much greater in adults than in children (P < 0.0001) for all the bone parameters (mid-distal radius, +6.6% versus +15.6%; third-distal radius, +6.9% versus +13.3%, for BMC). Epiphyseal bone enduring longitudinal growth showed a great capacity to respond to mechanical loading in children. Prolonging tennis playing into adulthood was associated with further increase in bone mineralization at diaphyseal skeletal sites. These findings illustrate the benefits of practicing impact-loading sports during growth and maintaining physical activity into adulthood to enhance bone mass accrual and prevent fractures later in life.

Effects of age, grip strength and smoking on forearm volumetric bone mineral density and bone geometry by peripheral quantitative computed tomography: comparisons between female and male

Peripheral quantitative computed tomography (pQCT) is useful to measure volumetric bone mineral density (vBMD) distinguishing trabecular from cortical bones as well as quantity of bone geometry. In the present study, we examined the effects of age, grip strength and smoking on vBMD, bone geometry and bone strength index (polar strength strain index (SSIp)), and then compared with the differences between female and male by employing pQCT in Japanese 252 female and 230 male subjects. Age was negatively correlated with vBMD, cortical area (Ct.Ar) and cortical thickness (Ct.Th) as well as SSIp in both sexes, and the correlation coefficients were higher in female, compared with those in male. Although age was correlated with endocortical circumferences (En.Le) in both sexes, periosteal circumferences (Ex.Le) were correlated with age only in male. Volumetric BMD, Ct.Ar, Ct.Th and SSIp were significantly lower in the group with vertebral fractures, although En.Le and Ex.Le were similar between subjects with and without vertebral fractures. Grip strength was positively correlated with vBMD, Ct.Ar, Ct.Th as well as SSIp. The extent of correlation was much higher in female, compared with that in male. Ct.vBMD, Ct.Ar, Ct.Th and SSIp, but not trabecular vBMD, were significantly lower in the group with high Brinkman index (number of cigarettes smoked per day) x (duration of smoking (years)) in female. These parameters were not significantly different between groups with high and low Brinkman index in male. In conclusion, the present study demonstrated that age, grip strength and smoking affected forearm vBMD, bone geometry and bone strength index by pQCT. These effects were greater in female, compared with those in male.

Bone status in elite male runners

The aim of our study was to compare long distance runners to body mass index (BMI)- and age-matched healthy controls with respect to bone parameters at all relevant loaded and nonloaded skeletal sites. Furthermore, we assessed the effect of running volume on bone parameters. Twenty elite male runners (21.1 km<1:15 h; volume >75 km/week/year) participated in the study (RG), 11 age- and BMI-matched male subjects (28+/-5 years) served as nontraining controls (CG). Subjects with any medication or illness affecting bone metabolism or with a family history of osteoporosis were not included. Bone parameters at various sites (total body, lumbar spine, femoral neck/hip, calcaneus) were measured by dual energy X-ray (DXA), quantitative computed tomography and quantitative ultrasound. Body composition was assessed via DXA and bioimpedance analysis; nutritional parameters were determined by 5-day dietary protocols. Training variables were assessed by questionnaires. Compared with nontraining controls runners had significantly higher BMD at all loaded sites (calcaneus, lower limbs, femoral neck, pelvis, and trabecular lumbar spine). BMD at nonloaded sites (ribs, upper limbs, and skull) was slightly but not significantly higher in the runners. We observed a low (r=0.30), nonsignificant association between training volume (km/week/year) and trabecular BMD of the femoral neck, which disappeared after adjusting for age, BMI, and body fat in this group of highly trained male runners. The effect of long distance running per se on bone parameters is not deleterious.

Calcium and Exercise Affect the Growing Skeleton

Adequate dietary calcium and bone-stimulating exercise during growth are known to affect skeletal development, but the combined effects of dietary calcium and osteogenic exercise have received scant attention. Animal research has showed a compensatory effect of impact loading on calcium-deprived bones, while various human studies have suggested compensatory, additive, or possibly synergistic effects in certain skeletal locations. Current evidence suggests that the best strategy for strong bones by the end of childhood may be either high-impact exercise with a moderate or greater calcium intake or a combination of moderate-impact exercise and adequate calcium during growth.

Bone geometry in response to long-term tennis playing and its relationship with muscle volume: a quantitative magnetic resonance imaging study in tennis players

The benefit of impact-loading activity for bone strength depends on whether the additional bone mineral content (BMC) accrued at loaded sites is due to an increased bone size, volumetric bone mineral density (vBMD) or both. Using magnetic resonance imaging (MRI) and dual energy X-ray absorptiometry (DXA), the aim of this study was to characterize the geometric changes of the dominant radius in response to long-term tennis playing and to assess the influence of muscle forces on bone tissue by investigating the muscle-bone relationship. Twenty tennis players (10 men and 10 women, mean age: 23.1+/-4.7 years, with 14.3+/-3.4 years of playing) were recruited. The total bone volume, cortical volume, sub-cortical volume and muscle volume were measured at both distal radii by MRI. BMC was assessed by DXA and was divided by the total bone volume to derive vBMD. Grip strength was evaluated with a dynamometer. Significant side-to-side differences (P<0.0001) were found in muscle volume (+9.7%), grip strength (+13.3%), BMC (+13.5%), total bone volume (+10.3%) and sub-cortical volume (+20.6%), but not in cortical volume (+2.6%, ns). The asymmetry in total bone volume explained 75% of the variance in BMC asymmetry (P<0.0001). vBMD was slightly higher on the dominant side (+3.3%, P<0.05). Grip strength and muscle volume correlated with all bone variables (except vBMD) on both sides (r=0.48-0.86, P<0.05-0.0001) but the asymmetries in muscle parameters did not correlate with those in bone parameters. After adjustment for muscle volume or grip strength, BMC was still greater on the dominant side. This study showed that the greater BMC induced by long-term tennis playing at the dominant radius was associated to a marked increase in bone size and a slight improvement in volumetric BMD, thereby improving bone strength. In addition to the muscle contractions, other mechanical stimuli seemed to exert a direct effect on bone tissue, contributing to the specific bone response to tennis playing.

Bone mineral density differences between adolescent dancers and non-exercising adolescent females

STUDY OBJECTIVE

To compare the bone mineral density (BMD) of the axial and appendicular skeleton between regularly exercising collegiate dancers and age matched non-exercising young females between the age of 17 and 19 to assess the impact of weight-bearing exercises and menstrual status on BMD.

DESIGN

Prospective observational cohort.

SETTING

Sports clinic in a collegiate school of dance and a hospital-based adolescent clinic.

PARTICIPANTS

The adolescent dancers consisted of full-time collegiate dance students from a tertiary Performing Arts Institute (n = 35). The non-exercising controls consisted of eumenorrhoeic patients of the same age presenting to the Adolescent Clinic (n = 35).

INTERVENTIONS

All subjects had a full hormonal profile, bio-impedance estimation of body fat, and dual energy X-ray absorptiometry and quantitative peripheral CT scans (pQCT) to determine bone density.

MAIN OUTCOME MEASURES

Comparison of the mean bone mineral density in the axial and appendicular skeleton between the two groups.

RESULTS

The incidence of oligo/amenorrhoea in the dancers was 20%. The lumbar spine BMD (1.006 g/cm(2) vs. 0.938, P = 0.048) and hip BMD (neck of femur 0.978 g/cm(2) vs. 0.838, P < 0.001; Ward's triangle 0.816 g/cm(2) vs. 0.720, P = 0.003; trochanter 0.777 g/cm(2) vs. 0.682; P < 0.001) were significantly higher in the eumenorrhoeic dancers as compared to controls. The radial BMD as measured by pQCT did not differ between the two groups, but the core trabecular tibial BMD was also higher in the dancers (321 mg/cm(3) vs. 286, P = 0.006). When only oligo/amenorrhoeic dancers (n = 7) were compared with the controls, the same differences in BMD values were no longer observed.

CONCLUSION

Young women undergoing regular intensive weight-bearing exercises as in the collegiate dancers here studied have higher BMD in the axial and appendicular skeleton as compared to non-exercising females of the same age if they remain eumenorrhoeic during their training. This advantage was apparently lost when they developed oligo/amenorrhoea.

Femoral neck structure in adult female athletes subjected to different loading modalities

Loading modality is a strong external determinant of structure and concomitant strength of the femoral neck. Particularly effective seem to be loadings, which arise from high impacts or impacts from atypical loading directions.

INTRODUCTION

Physical loading plays an important role, not only in the process of bone modeling and remodeling, but also in shaping a mechanically appropriate bone structure. This study aimed at testing the hypothesis that the type of loading partly determines the femoral neck structure.

MATERIALS AND METHODS

A total of 255 premenopausal female athletes representing volleyball, hurdling, squash-playing, soccer, speed skating, step aerobics, weight-lifting, orienteering, cross-country skiing, cycling, and swimming and their 30 nonathletic counterparts were measured with DXA. Besides the conventional areal BMD (aBMD) of the femoral neck, the hip structure analysis (HSA) was used to estimate the cross-sectional area (CSA), subperiosteal width (W), and section modulus (Z, an index of bone strength) at the narrowest section of the femoral neck. Also, training history, muscle strength, and calcium intake were assessed. The above-mentioned sports were classified according to the type of loading they apparently produce at the hip region; that is, high-impact loading (volleyball, hurdling), odd-impact loading (squash-playing, soccer, speed-skating, step aerobics), high-magnitude loading (weightlifting), low-impact loading (orienteering, cross-country skiing), and nonimpact loading (swimming, cycling).

RESULTS

High-impact and odd-impact loading sports were associated with the highest age-, weight-, and height-adjusted aBMD (23% and 29% higher values compared to nonathletic referents), CSA (22% and 27%), and Z (22% and 26%). In contrast, repetitive, nonimpact loading sports were not associated with any clear benefit in any bone value compared with the referents. The W at the narrowest femoral neck section was similar in all groups. Body height and weight accounted virtually for one-half of the variation in Z, whereas the type of loading predicted 13% of the total variation of this variable-clearly more than the 2% attributable to isometric leg extension strength. Both high-impact and odd-impact loading modalities were associated with a large benefit in Z, corresponding to >1 SD in the reference group, whereas repetitive, low-impact loading showed a benefit that was only one-half of that. Surprisingly, high-magnitude loading (weightlifting) was not associated with a statistically significant increase in Z.

CONCLUSION

We conclude that mechanical loading and its modality are strong external determinants of structure and concomitant strength of the femoral neck. Particularly effective seem to be loadings, which arise from high impacts or impacts from atypical loading directions.

The clinical significance of serum osteocalcin and N-terminal propeptide of type I collagen in predialysis patients with chronic renal failure

Several new serum markers for bone metabolism have recently become available and are being applied to clinical practice. Their clinical usefulness in predialysis patients with chronic renal failure (CRF), however, has not yet been determined. Serum levels of three bone formation markers-bone alkaline phosphatase (BAP), osteocalcin (OC), and N-terminal propeptide of type I collagen (PINP)-and three bone resorption markers-type I collagen cross-linked N-telopeptide (NTx), deoxypyridinoline (DPD), and pyridinoline (PYD)-were measured simultaneously in 85 predialysis CRF patients (serum creatinine 3.5 +/- 1.9 mg/dl, 61.0 +/- 10.9 years old, 54 males and 31 females, 36 diabetics and 49 nondiabetics) to examine the relationships between these markers and bone mineral density (BMD) of the distal radius, as measured by peripheral quantitative computed tomography (pQCT). Trabecular BMD, which is strongly affected by bone metabolism, was significantly negatively correlated with each of the bone formation markers (r=-0.341, p=0.0016, for OC; r=-0.314, p=0.0036, for PINP; r=-0.238, p=0.0315, for BAP), but there was no significant correlation between BMD and any of the bone resorption markers. In multivariate regression analyses (adjusted by age, sex, presence of diabetes, glomerular filtration rate, intact parathyroid hormone, calcium, phosphate, and 1,25-dihydroxyvitamin D), OC and PINP were significantly associated with a decrease in BMD, but BAP was not. In conclusion, we demonstrated that in predialysis CRF patients, BMD of the distal radius, particularly of trabecular bone, is associated with serum OC and PINP levels. OC and PINP are suggested to be possible parameters for the clinical evaluation of the effect of bone metabolism on BMD.

Loading and bone fragility

Data from retrospective and prospective observational and case-control studies suggest that activity is associated with reduced fracture risk, but consistently replicated bias may be responsible for this desired endpoint. Exercise during growth is likely to build a larger and stronger skeleton. However, cessation of exercise may erode the benefits. Modeling changes produced by exercise during growth may be permanent; remodeling changes may not be. Exercise during adulthood produces small increments in BMD or may prevent bone loss. Absence of evidence is not evidence of absence of effect, but the null hypothesis that exercise has no effect on fracture rates in old age cannot be rejected by any published data. Proof requires demonstration of a reduction in spine and hip fractures in well-designed and well-executed prospective randomized studies; none exists. Blinded studies cannot be done, but open trials can and should be done.

Relationship between the duration of paralysis and bone structure: a pQCT study of spinal cord injured individuals

The aim of the present study was to describe bone loss of the separate compartments of trabecular and cortical bone, as well as changes in bone geometry of a large number of spinal cord injured (SCI) individuals. Eighty-nine motor complete spinal cord injured men (24 tetraplegics and 65 paraplegics) with a duration of paralysis of between 2 months and 50 years were included in the study. Distal epiphyses and midshafts of the femur, tibia, and radius were measured by peripheral quantitative computed tomography. The same measurements were performed in a reference group of 21 healthy able-bodied men of the same age range. In the femur and tibia, bone mass, total and trabecular bone mineral density (BMDtot and BMDtrab, respectively) of the epiphyses, as well as bone mass and cortical cross-sectional area of the diaphyses, showed an exponential decrease with time after injury in the spinal cord injured subjects. The decreasing bone parameters reached new steady states after 3-8 years, depending on the parameter. Bone mass loss in the epiphyses was approximately 50% in the femur and 60% in the tibia, while the shafts lost only approximately 35% in the femur and 25% in the tibia. In the epiphyses, bone mass was lost by reducing BMD, while in the shaft bone mass was lost by reducing cortical wall thickness, a process achieved by endosteal resorption advancing at a rate of about 0.25 mm/year within the first 5-7 years after injury. Except for a slight transient decrease in cortical BMD of the femoral and tibial shaft during the first 5 years after the spinal cord lesion, cortical BMD of the spinal cord injured subjects was found to be at reference values. Bone parameters of the radial epiphysis in paraplegic subjects showed no deficits compared to the reference group. Furthermore, a trend for an increased radial shaft diameter suggests periosteal apposition as a consequence of increased loading of the arms.

Cortical and trabecular bone at the forearm show different adaptation patterns in response to tennis playing

Bone responds to impact-loading activity by increasing its size and/or density. The aim of this study was to compare the magnitude and modality of the bone response between cortical and trabecular bone in the forearms of tennis players. Bone area, bone mineral content (BMC), and bone mineral density (BMD) of the ulna and radius were measured by dual-energy X-ray absorptiometry (DXA) in 57 players (24.5 +/- 5.7 yr old), at three sites: the ultradistal region (50% trabecular bone), the mid-distal regions, and third-distal (mainly cortical bone). At the ultradistal radius, the side-to-side difference in BMD was larger than in bone area (8.4 +/- 5.2% and 4.9 +/- 4.0%, respectively, p < 0.01). In the cortical sites, the asymmetry was lower (p < 0.01) in BMD than in bone area (mid-distal radius: 4.0 +/- 4.3% vs 11.7 +/- 6.8%; third-distal radius: 5.0 +/- 4.8% vs 8.4 +/- 6.2%). The asymmetry in bone area explained 33% of the variance of the asymmetry in BMC at the ultradistal radius, 66% at the mid-distal radius, and 53% at the third-distal radius. The ulna displayed similar results. Cortical and trabecular bone seem to respond differently to mechanical loading. The first one mainly increases its size, whereas the second one preferentially increases its density.

Femoral neck response to exercise and subsequent deconditioning in young and adult rats

Aged bones have been considered to have reduced capacity to respond to changes in incident loading. By subjecting young and adult rats to increased loading and subsequent deconditioning, we observed quantitatively similar adaptive responses of bone in these two groups, but young skeletons adapted primarily through geometric changes and adult bones through increased volumetric density. Loss of the exercise-induced bone benefits did not depend on age.

INTRODUCTION

Aging has been shown to decrease the sensitivity of the mechanosensory cells of bones to loading-induced stimuli, presumably resulting in not only reduced capacity but also different adaptive mechanism of the aged skeleton to altered loading, as well as poorer capacity to preserve exercise-induced bone benefits.

MATERIALS AND METHODS

Fifty young (5-week-old) and 50 adult (33-week-old) male rats were randomized into control and exercise (+deconditioning) groups. After a 14-week progressively intensified running program, one-half of the exercised rats (both young and adult) were killed, and the remaining rats underwent subsequent 14-week period of deconditioning (free cage activity). A comprehensive analysis of the femoral neck was performed using peripheral quantitative computed tomography and mechanical testing.

RESULTS

In comparison with the controls, both young and adult exercised rats had significant increases in almost all measured parameters: +25% (p < 0.001) and +10% (not significant [NS]) in the cross-sectional area; +28% (p < 0.001) and +18% (p < 0.001) in bone mineral content; +11% (p < 0.05) and +23% (p < 0.001) in bone mineral density; and +30% (p < 0.01) and +28% (p < 0.01) in the breaking load, respectively. The skeletal responses were not statistically different between the young and adult rats. After the 14-week period of deconditioning, the corresponding exercised-to-controls differences were +17% (p < 0.05) and +10% (NS), +18% (p < 0.05) and +13% (p < 0.05), +2% (NS) and +2% (NS), and +11% (NS) and +6% (NS), respectively. Again, the response differences were not significant between the age groups.

CONCLUSION

Quantitatively, the capacity of the young and adult skeleton to adapt to increased loading was similar, but the adaptive mechanisms appeared different: growing bones seemed to primarily display geometric changes (increase in bone size), whereas the adult skeleton responded mainly through an increase in density. Despite this apparent difference in the adaptive mechanism, aging did not modulate the ability of the skeleton to preserve the exercise-induced bone gain, because the bone loss was similar in the young and adult rats after cessation of training.

Effects of physical training on cortical bone at midtibia assessed by peripheral QCT

Effects of long-term exercise on volumetric bone mineral density (vBMD), bone mineral content, bone geometric properties, and the strength indexes of bone were examined in a cross-sectional study of athletes and controls. Tibias of 25 jumpers (13 women), 30 swimmers (15 women), and 25 controls (15 women), aged 18-23 yr, were scanned at midsite by using peripheral quantitative computed tomography. The cortical vBMD of female athletes was lower than that of the controls (2.00 +/- 0.05, 1.90 +/- 0.08, and 1.92 +/- 0.12 g/cm3, respectively, for controls, swimmers, and jumpers). On the other hand, periosteal areas of male jumpers and female athletes were greater than that of controls (460 +/- 50, 483 +/- 46, and 512 +/- 55 mm2, respectively, for male controls, swimmers, and jumpers, and 283 +/- 52, 341 +/- 73, and 378 +/- 75 mm2, respectively, for female controls, swimmers, and jumpers). The endocortical area of female swimmers was greater than that of controls (103 +/- 29, 148 +/- 52, and 135 +/- 54 mm2, respectively, for controls, swimmers, and jumpers). The polar moment of inertia and strength strain index of male jumpers and female athletes were significantly greater than those of controls, except for the difference in strength strain index between male jumpers and controls. We conclude that the improvement of mechanical properties of young adult bone in response to long-term exercise is related to geometric adaptation and not to vBMD.

The Erlangen Fitness Osteoporosis Prevention Study: a controlled exercise trial in early postmenopausal women with low bone density-first-year results

OBJECTIVE

To investigate the effect of a 2-year vigorous, combined high-impact, strength, and endurance training program on bone mineral density (BMD) determined by dual-energy x-ray absorptiometry (DXA), quantitative computed tomography (QCT), and ultrasound in early postmenopausal women with osteopenia.

DESIGN

Nonrandomized controlled trial, reporting 1-year data.

SETTING

Community.

PARTICIPANTS

Early postmenopausal (1-8y postmenopausal) osteopenic women (DXA T score at lumbar spine or total hip between -1 and -2.5 standard deviations). The exercise group (n=59; mean age, 55.1+/-3.4y) and control group (n=41; mean age, 55.9+/-3.1y) were recruited from community registers.

INTERVENTION

Fourteen months of exercise training, with 2 joint sessions and 2 additional home training sessions. Exercise and control groups were supplemented individually with calcium and cholecalciferol up to 1500mg of calcium and 500IU of vitamin D per day.

MAIN OUTCOMES MEASURES

BMD at the lumbar spine and total hip measured by DXA, isometric maximum strength, and maximal oxygen consumption (VO2max) during a stepwise running test to exhaustion.

RESULTS

Bone density increased significantly at the lumbar spine for the exercise group (1.3%, P<.001) and decreased in the control group (-1.2%, P<.01). Differences at the total hip (-0.3%, not significant vs -0.8%, P<.05) and the femoral neck (-0.8%, P<.05 vs -1.8%, P<.001) were nonsignificant. Changes in isometric maximum strength were significant for each region (grip strength, trunk flexors and extensors, hip flexors, leg adductors and abductors, arm flexors and extensors) in the exercise group (11%-39%) compared with nonrelevant changes (-1.1% to 3.9%) in the control group. Between-group differences were significant (P<.01-.001) for all strength parameters. VO2max increased significantly by 11% (P<.001) in the exercise group but decreased in the control group by 4% (P<.05) while showing significant between-group differences.

CONCLUSION

High-intensity exercise training can have a positive influence on bone density in early postmenopausal osteopenic women.

Effect of long-term impact-loading on mass, size, and estimated strength of humerus and radius of female racquet-sports players: a peripheral quantitative computed tomography study between young and old starters and controls

Bone characteristics of the humeral shaft and distal radius were measured from 64 female tennis and squash players and their 27 age-, height-, and weight-matched controls with peripheral quantitative tomography (pQCT) and dual energy X-ray absorptiometry (DXA). The players were divided into two groups according to the starting age of their tennis or squash training (either before or after menarche) to examine the possible differences in the loading-induced changes in bone structure and volumetric density. The following pQCT variables were used: bone mineral content, total cross-sectional area of bone (TotA), cross-sectional area of the marrow cavity (CavA) and that of the cortical bone (CoA), cortical wall thickness (CWT), volumetric density of the cortical bone (CoD) and trabecular bone (TrD), and torsional bone strength index for the shaft (BSIt) and compressional bone strength index for the bone end (BSIc). These bone strength indices were compared with the DXA-derived areal bone mineral density (aBMD) to assess how well the latter represents the effect of mechanical loading on apparent bone strength. At the humeral shaft, the loaded arm's greater bone mineral content (an average 19% side-to-side difference in young starters and 9% in old starters), was caused by an enlarged cortex (CoA; side-to-side differences 20% and 9%, respectively). The loaded humerus seemed to have grown periosteally (the CavA did not differ between the sites), leading to 26% and 11% side-to-side BSIt differences in the young and old starters, respectively. CoD was equal between the arms (-1% difference in both player groups). The side-to-side differences in the young starters' bone mineral content, CoA, TotA, CWT, and BSIt were 8-22% higher than those of the controls and 8-14% higher than those of the old starters. Old starters' bone mineral content, CoA, and BSIt side-to-side differences were 6-7% greater than those in the controls. The DXA-derived side-to-side aBMD difference was 7% greater in young starters compared with that of the old starters and 14% compared with that in controls, whereas the difference between old starters and controls was 6%, in favor of the former. All these between-group differences were statistically significant. At the distal radius, the player groups differed significantly from controls in the side-to-side bone mineral content, TrD, and aBMD differences only: the young starters' bone mineral content difference was 9% greater, TrD and aBMD differences were 5% greater than those in the controls, and the old starters' TrD and aBMD differences were both 7% greater than those in the controls. In summary, in both of the female player groups, the structural adaptation of the humeral shaft to long-term loading seemed to be achieved through periosteal enlargement of the bone cortex, although this adaptation was clearly better in the young starters. Exercise-induced cortical enlargement was not so clear at the distal radius (a trabecular bone site), and the study suggested that at long bone ends, the trabecular density could be a modifiable factor to built a stronger bone structure. Conventional DXA-based aBMD measurement detected the intergroup differences in the exercise-induced bone gains, although, because it measured two dimensions of bone only, it seemed to underestimate the effect of exercise on the apparent bone strength, especially if the playing had been started during the growing years.

Osteoblastic cells have refractory periods for fluid-flow-induced intracellular calcium oscillations for short bouts of flow and display multiple low-magnitude oscillations during long-term flow

Partitioning a daily mechanical stimulus into discrete loading bouts enhances bone formation in rat tibiae (J. Bone Mineral Res. 15(8) (2000) 1596). We hypothesized that a refractory period exists in primary rat osteoblastic cells, during which fluid-flow-induced [Ca(2+)](i) oscillations are insensitive to additional short bouts (2 min) of fluid flow. Because the frequency of [Ca(2+)](i) oscillations is believed to be important for regulating cellular activity and long-term fluid flow alters gene expression in bone cells, we also hypothesized that long-term (15 min) oscillating fluid flow produces multiple [Ca(2+)](i) oscillations in osteoblastic cells. Primary osteoblastic cells from rat long bones were exposed to 2 min of oscillating fluid flow that produced shear stresses of 2 Pa at 2 Hz. After a rest period of 5, 30, 60, 300, 600, 900, 1800, or 2700 s, the cells were exposed to a second 2-min bout of flow. A 600 s rest period was required to recover the percentage of cells responding to fluid flow and a 900 s rest period was required to recover the [Ca(2+)](i) oscillation magnitude. The magnitude and shape of the two [Ca(2+)](i) oscillations were strikingly similar for individual cells after a 900 s rest period. During 15 min of continuous oscillating flow, some individual cells displayed between 1 and 9 oscillations subsequent to the initial [Ca(2+)](i) oscillation. However, only 54% of the cells that responded initially displayed subsequent [Ca(2+)](i) oscillations during long-term flow and the magnitude of the subsequent oscillations was only 28% of the initial response.

Effect of long-term impact-loading on mass, size, and estimated strength of humerus and radius of female racquet-sports players: a peripheral quantitative computed tomography study between young and old starters and controls

Bone characteristics of the humeral shaft and distal radius were measured from 64 female tennis and squash players and their 27 age-, height-, and weight-matched controls with peripheral quantitative tomography (pQCT) and DXA. The players were divided into two groups according to the starting age of their tennis or squash training (either before or after menarche) to examine the possible differences in the loading-induced changes in bone structure and volumetric density. The used pQCT variables were bone mineral content (BMC), total cross-sectional area (TotA) of bone, cross-sectional area of the marrow cavity (CavA) and that of the cortical bone (CoA), cortical wall thickness (CWT), volumetric density of the cortical bone (CoD) and trabecular bone (TrD), and torsional bone strength index (BSIt) for the shaft, and compressional bone strength index (BSIc) for the bone end. These bone strength indices were compared with the DXA-derived areal bone mineral density (aBMD) to assess how well the latter represents the effect of mechanical loading on apparent bone strength. At the humeral shaft, the loaded arm's greater BMC (an average 19% side-to-side difference in young starters and 9% in old starters) was caused by an enlarged cortex (CoA; side-to-side differences 20% and 9%, respectively). The loaded humerus seemed to have grown periosteally (the CavA did not differ between the sites) leading to 26% and 11% side-to-side BSIt difference in the young and old starters, respectively. CoD was equal between the arms (-1% difference in both player groups). The side-to-side differences in the young starters' BMC, CoA, TotA, CWT, and BSIt were 8-22% higher than those of the controls and 8-14% higher than those of the old starters. Old starters' BMC, CoA, and BSIt side-to-side differences were 6-7% greater than those in the controls. The DXA-derived side-to-side aBMD difference was 7% greater in young starters compared with that of the old starters and 14% compared with that in controls, whereas the difference between old starters and controls was 6%, in favor of the former. All these between-group differences were statistically significant. At the distal radius, the player groups differed significantly from controls in the side-to-side BMC, TrD, and aBMD differences only; the young starters' BMC difference was 9% greater, TrD and aBMD differences were 5% greater than those in the controls, and the old starters' TrD and aBMD differences were both 7% greater than those in the controls. In summary, in both of the female player groups the structural adaptation of the humeral shaft to long-term loading seemed to be achievedthrough periosteal enlargement of the bone cortex although this adaptation was clearly better in the young starters. Exercise-induced cortical enlargement was not so clear at the distal radius (a trabecular bone site), and the study suggested that at long bone ends also the TrD could be a modifiable factor to build a stronger bone structure. The conventional DXA-based aBMD measurement detected the intergroup differences in the exercise-induced bone gains, although, measuring two dimensions of bone only, it seemed to underestimate the effect of exercise on the apparent bone strength, especially if the playing had been started during the growing years.

Potential role of vitamin D receptor gene polymorphism in determining bone phenotype in young male athletes

The genetic difference among individuals partly explains variance in adaptive response to exercise through gene-environment interaction. The aim of this cross-sectional study was to evaluate the role of the vitamin D receptor (VDR) gene polymorphism, which locates at the translation initiation site, in the adaptations of bone to long-term impact loading. The VDR genotypes, as detected by endonuclease Fok I, and bone phenotypes of the lumbar spine and femoral neck were examined in 44 highly trained young male athletes and 44 age-matched nonathletic controls. As a whole, the athletes had a significantly higher bone mineral content resulting from a combination of increased volume and density at both sites than the controls. When the athletes were compared with the controls within each VDR genotype, however, the increased spinal volume was found only in the athletes with the FF but not in those with the Ff genotype("F" for the absence of the endonuclease Fok I restriction site and "f" for its presence). Differences in bone mineral content in the lumbar spine and femoral neck between the controls and the athletes were greater in subjects with FF than those with Ff. Our results suggest a gene-environment interaction in that the bone phenotypes in individuals with FF adapt to impact loading by producing stronger bone structure than those with the Ff do.

Paradoxical adaptation of mature radius to unilateral use in tennis playing

The positive effects of physical activity on human bone mass have been well documented in many cross-sectional studies comparing athletes with sedentary controls as well as in longitudinal follow-up. By applying peripheral quantitative computed tomography (pQCT), which has the advantage of measuring volumetric bone mineral density (BMD) and the ability to distinguish among trabecular and cortical components, it was demonstrated that cortical BMD of the dominant arm was not greater than that of the nondominant arm. Cortical drift toward the periosteal direction and an increase in cortical thickness resulted in an improvement of mechanical characteristics of the playing arm's midradius. An improvement in the mechanical properties of young adult bone in response to long-term exercise was therefore related to geometric adaptation, but not to an increase in BMD. The manner in which the recruitment and function of bone cells are coordinated differs between the growing and the nongrowing skeleton. In the former, modeling is the dominant mode, and in the latter it is remodeling. In the present study, the side-to-side difference of 92 middle-aged female tennis players who initiated training after bone had matured was analyzed by pQCT. The side-to-side difference detected suggested a paradoxical adaptation of the mature radius to unilateral use during tennis playing, and that tennis playing after bone had matured did not stimulate cortical drift in the periosteal direction, unlike that seen in young subjects. Unexpectedly, the cross-sectional areas (periosteal and endocortical area) of the radius were smaller in the dominant arm than in the nondominant arm in the middle-aged female players. The findings suggest that unilateral use of the arm after the third decade of life suppresses age-related changes in bone geometry.

Associations of calcium intake and physical activity with bone density and size in premenopausal and postmenopausal women: a peripheral quantitative computed tomography study

The purpose of this cross-sectional study was to examine the impact of long-term physical activity (PA) and calcium intake on non-weight-bearing radius and weight-bearing tibia. Altogether, 218 healthy, nonsmoking women, [92 premenopausal women, mean age, 32.6 years (SD, 2.2 years), and 126 postmenopausal women, mean age, 67.3 years (SD, 2.0 years)] participated. The subjects were divided according to their habitual levels of physical activity (PA+ or PA-) and calcium intake (Ca+ or Ca-). The distal end and shaft regions of the radius and tibia were evaluated with peripheral quantitative tomography (pQCT). For the shaft regions, bone mineral content (BMC), cortical cross-sectional area (CoA), cortical density (CoD), and bone strength index, that is, 1-11.9% of the density-weighted section modulus (BSI) were determined. For the distal ends, BMC, total cross-sectional area (ToA), trabecular density (TrD), and BSI were determined. The BMC at the distal radius in the young PA+ group was 6.6% (95% CI, 1- to 11.9%) lower than that of the PA- group. A similar nonsignificant trend was found for the radial shaft. The radial shaft showed a mechanically more competent structure among the older subjects with a BSI 8.5% (95% CI, 1.8-15.6%) higher in the older PA+ group than in the older PA- group. The associations between calcium intake and the radial bone characteristics were systematically positive in both age groups. PA seemed to benefit the distal tibia. In the younger age group the TrD was 6.9% (95% CI, 1.8-12.4%) higher in the PA+ group, and in the elderly the BMC was 5% (95% CI, 0.3-9.9%) higher in the PA+ group than in the PA- group. Note that in the younger age group the ToA was 5.1% (95% CI, 0-9.1%) smaller in the PA+ group than in the PA- group, and in the older age group the ToA was 4.2% (95% CI, -0.3-8.9%) greater in the PA+ group than in the PA- group. The association of PA and bone characteristics at the tibial shaft was positive in both age groups (statistically significant for the older subjects). The tibial shaft BSI of the older PA+ group was 8.6% (95% CI, 2.6-14.9%) better than that of the old PA- group. There was no association between calcium intake and the tibial bone characteristics in either age group. In conclusion, high calcium intake was positively associated with a mechanically competent structure in the radius among both younger and older women, whereas the influence of PA did not become apparent until older ages. PA seemed to benefit particularly the weight-bearing tibia, whereas calcium intake was not associated with the tibia.

Lateralized mineral content and density in distal forearm bones in right-handed men and women: relation of structure to function

To test whether handedness has an asymmetric effect on distal forearm bone mineral content (BMC) and bone mineral density (BMD), and whether there is an effect of sex on these variables, the mean BMCs and BMDs in bilateral distal forearms were compared in right-handed men and women. It was expected that the BMC and BMD would be higher on the right than the left side in right-handers. The present results were consistent with this working hypothesis. Namely, the right-BMCs were found to be significantly higher than left-BMCs for all regions of the bones studied. There were no sex differences either for the right-left BMCs or for the right-left BMDs. The results indicated that i) the relation of structure to function would also be valid outside the brain, ii) the mean BMCs, but not BMDs, were significantly higher in the right than the left arm at different distal forearm regions, and iii) there were no significant sex differences in the distal-forearm BMCs and BMDs.

Determination of bone size of hip, spine, and wrist in human pedigrees by genetic and lifestyle factors

Osteoporosis is a major public health problem defined as a loss of bone strength, of which bone size is an important determinant. Compared with extensive studies on bone mass, studies on the importance of factors determining variation in bone size are relatively few. In particular, the significance of genetic factors is largely unknown. In 49 pedigrees with 703 subjects bone sizes of the hip, spine, and wrist were measured by dual X-ray absorptiometry. We evaluated the contribution of genetic factors in determining variation in bone size of the hip, spine, and wrist while studying age, sex, weight, height, exercise, smoking, alcohol consumption, and the interaction among these factors as covariates for their effects on bone size. We found that, on average, males have larger bone sizes. Male bone sizes at the spine and hip increased with age; however, the effect of age in our female subjects was nonsignificant. Height invariably affected bone size at all the sites studied. Alcohol consumption and exercise generally had significant effects in increasing bone size at the spine and/or hip in both males and females. After adjusting for sex, age, weight, height, lifestyle factors, and the significant interactions among these factors, heritabilities (+/-SE) were, respectively, 0.48 (0.09), 0.64 (0.08), and 0.60 (0.09) for bone size at the hip, spine, and wrist.

Flow-induced calcium oscillations in rat osteoblasts are age, loading frequency, and shear stress dependent

Bone adaptation to mechanical loading is dependent on age and the frequency and magnitude of loading. It is believed that load-induced fluid flow in the porous spaces of bone is an important signal that influences bone cell metabolism and bone adaptation. We used fluid flow-induced shear stress as a mechanical stimulus to study intracellular calcium (Ca) signaling in rat osteoblastic cells (ROB) isolated from young, mature, and old animals. Fluid flow produced higher magnitude and more abundant [Ca(2+)](i) oscillations than spontaneous oscillations, suggesting that flow-induced Ca signaling encodes a different cellular message than spontaneous oscillations. ROB from old rats showed less basal [Ca(2+)](i) activity and were less responsive to fluid flow. Cells were more responsive to 0.2 Hz than to 1 or 2 Hz and to 2 Pa than to 1 Pa. These data suggest that the frequency and magnitude of mechanical loading may be encoded by the percentage of cells displaying [Ca(2+)](i) oscillations but that the ability to transduce this information may be altered with age.