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

Development of Upper-Extremity Morphological Asymmetries in Male and Female Elite Youth Tennis Players: A Longitudinal Study

PURPOSE

This 2-year longitudinal study examined the development of upper-extremity bone mineral density (BMD), bone mineral content (BMC), and lean mass (LM) asymmetry magnitudes in male and female youth tennis players.

METHODS

Dominant and nondominant upper-extremity BMD, BMC, and LM values of 49 male and 31 female players were measured yearly using dual X-ray absorptiometry. From these values, asymmetry magnitudes were calculated and expressed as a percentage. Maturity offset was estimated using anthropometric measurements. Linear mixed effect models examined the development of BMD, BMC, and LM asymmetry magnitudes according to players' maturity offset, sex, and training volume.

RESULTS

Adjusted for sex and training volume, a 1-year increment in maturity offset was associated with a significant increase in BMD (1.3% [2.2%]; P < .001) and BMC (0.6% [2.4%]; P = .011) asymmetry magnitudes. Male players displayed significantly higher LM asymmetry magnitudes (Δ3.2% [8.4%]; P = .002) compared with their female counterparts. Training volume was not significantly associated with asymmetry magnitude development.

CONCLUSION

In contrast to LM, male and female youth tennis players' upper-extremity bones are still responsive to mechanical loading with a significant increase in BMD and BMC asymmetry magnitudes according to maturity offset.

Digital wrist tomosynthesis (DWT)-based finite element analysis of ultra-distal radius differentiates patients with and without a history of osteoporotic fracture

Despite effective therapies for those at risk of osteoporotic fracture, low adherence to screening guidelines and limited accuracy of bone mineral density (BMD) in predicting fracture risk preclude identification of those at risk. Because of high adherence to routine mammography, bone health screening at the time of mammography using a digital breast tomosynthesis (DBT) scanner has been suggested as a potential solution. BMD and bone microstructure can be measured from the wrist using a DBT scanner. However, the extent to which biomechanical variables can be derived from digital wrist tomosynthesis (DWT) has not been explored. Accordingly, we measured stiffness from a DWT based finite element (DWT-FE) model of the ultra-distal (UD) radius and ulna, and correlate these to reference microcomputed tomography image based FE (μCT-FE) from five cadaveric forearms. Further, this method is implemented to determine in vivo reproducibility of FE derived stiffness of UD radius and demonstrate the in vivo utility of DWT-FE in bone quality assessment by comparing two groups of postmenopausal women with and without a history of an osteoporotic fracture (Fx; n = 15, NFx; n = 51). Stiffness obtained from DWT and μCT had a strong correlation (R2 = 0.87, p < 0.001). In vivo repeatability error was <5 %. The NFx and Fx groups were not significantly different in DXA derived minimum T-scores (p > 0.3), but stiffness of the UD radius was lower for the Fx group (p < 0.007). Logistic regression models of fracture status with stiffness of the nondominant arm as the predictor were significant (p < 0.01). In conclusion this study demonstrates the feasibility of fracture risk assessment in mammography settings using DWT imaging and FE modeling in vivo. Using this approach, bone and breast screening can be performed in a single visit, with the potential to improve both the prevalence of bone health screening and the accuracy of fracture risk assessment.

Development of upper and lower extremity functional asymmetries in male and female elite youth tennis players: a longitudinal study

BACKGROUND

This longitudinal study aimed to examine the development of both upper and lower extremity functional performances, together with asymmetry magnitudes and directionality in youth tennis players.

METHODS

Dominant and non-dominant physical performance values of 90 players (53 males, 37 females) were determined yearly (with monitoring up to 3 years) using unilateral strength, power, speed and agility tests from which asymmetry magnitude percentages were calculated. Linear mixed effect models examined the development of performance values according to youth players' maturity offset, performance dominance, sex and training volume. Similarly, the development of functional asymmetry magnitudes was examined according to players' maturity offset, sex and training volume. Kappa coefficients (k) examined the consistency in directionality across test occasions.

RESULTS

Regardless of sex, the dominant and non-dominant physical performance values of every test significantly (P<0.05) improved with increasing maturity offset. No sex differences were apparent except for strength and power related tests where male players performed significantly better. Functional asymmetry magnitudes (ranging from 2.0 to 15.9%) did not significantly change with increasing maturity offset (range=-0.3-0.4% per year). Training volume was not significantly associated with the performance values and asymmetry magnitudes. The dominant upper extremity (which holds the tennis racket) consistently displayed the dominant performance value (k value: 1.00) across test occasions, which was not the case at lower extremity level (k value range: -0.28-0.31).

CONCLUSIONS

The functional asymmetry magnitudes did not change significantly with youth tennis players' maturity offset over a 3-year period.

Rehabilitation: Neurogenic Bone Loss after Spinal Cord Injury

Osteoporosis is a common skeletal disorder which can severely limit one's ability to complete daily tasks due to the increased risk of bone fractures, reducing quality of life. Spinal cord injury (SCI) can also result in osteoporosis and sarcopenia. Most individuals experience sarcopenia and osteoporosis due to advancing age; however, individuals with SCI experience more rapid and debilitating levels of muscle and bone loss due to neurogenic factors, musculoskeletal disuse, and cellular/molecular events. Thus, preserving and maintaining bone mass after SCI is crucial to decreasing the risk of fragility and fracture in vulnerable SCI populations. Recent studies have provided an improved understanding of the pathophysiology and risk factors related to musculoskeletal loss after SCI. Pharmacological and non-pharmacological therapies have also provided for the reduction in or elimination of neurogenic bone loss after SCI. This review article will discuss the pathophysiology and risk factors of muscle and bone loss after SCI, including the mechanisms that may lead to muscle and bone loss after SCI. This review will also focus on current and future pharmacological and non-pharmacological therapies for reducing or eliminating neurogenic bone loss following SCI.

Body Composition and Strength Symmetry of Kettlebell Sport Athletes

Kettlebell sport (KBs) is increasingly popular, but very few studies have been focused on this discipline. This research aims to investigate the effects of KBs on body composition, strength symmetry, and segmental body composition symmetry in a sample of Italian elite athletes. Data were collected from a sample of 16 athletes of both sexes (11 men and 5 women; 34.5 ± 9.0 years of age). Anthropometric (height, weight, arm, thigh, calf, and waist circumferences), hand grip strength, and total and segmental bioelectrical variables were taken. Body composition was analysed by using specific bioelectrical impedance vector analysis (BIVA). Paired t-tests and confidence ellipses were applied to analyse bilateral differences. Elite athletes of both sexes showed high values of phase angle, indicative of high body cell mass and quality and proxy of muscle mass. Hand grip strength and body composition were symmetrical, with the only exception of a higher %FM in the right leg (Zsp: t = 3.556; p = 0.003). In conclusion, this study suggests that KBs contributes to muscle mass improvement, body composition, and strength symmetry, especially in the upper body.

The Association Between Chronological Age and Maturity Status on Lower Body Clinical Measurements and Asymmetries in Elite Youth Tennis Players

BACKGROUND

Tennis is one of the most popular sports among youths. At elite levels, a notable increase in injury incidence and a temporary decline in performance may occur when children progress through puberty. However, limited research has explored maturity-associated variations in clinical measurements suggested as predictors of injury and tennis performance in elite youth players. Therefore, the main purpose of this study was to analyze the association between chronological age and maturity status on several measures of neuromuscular capability and physical performance as well as bilateral (interlimb) asymmetries in elite youth tennis players.

HYPOTHESIS

Youth tennis players around peak height velocity (PHV) will show higher growth-related impairments or deficits in measures of neuromuscular capability and physical performance than their less (pre-PHV) and more (post-PHV) mature counterparts irrespective of sex.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 68 male (age, 13.7 ± 1.1 years; height, 162.4 ± 9.4 cm; body mass, 51.4 ± 10.3 kg [Mean values ± SD]) and 60 female (age, 13.6 ± 1.1 years; height, 162.8 ± 7.2 cm; body mass, 52.7 ± 7.5 kg [Mean values ± SD]) elite youth tennis players from 2 different age groups (under 13 [U13] and under 15 [U15]) and maturity status (pre-PHV, around PHV, and post-PHV), were tested during national training camps. Tests included the Y Balance Test, isometric hip abduction and adduction strength, hip ranges of motion (ROMs), and countermovement jump (CMJ) height. Bayesian analysis was used to establish any significant between-group differences.

RESULTS

Only dynamic balance (in boys; Bayesian factor [BF₁₀] = 88.2) and jump height (in both boys and girls; BF₁₀ >100) were significatively associated with chronological age, whereby the U15 group showed lower Y Balance Test reach distances (-6%; standardized effect size δ = 0.62) but higher CMJ height scores (+18%; δ = 0.73) than the U13 group. Although boys jump higher (+11%; δ = 0.62) and were stronger in isometric hip adduction strength (+14%; δ = 0.92) than girls, the latter had greater hip internal ROM values (+15%; δ = 0.75). Furthermore, relevant maturity-associated effects (BF₁₀ = 34.6) were solely observed for the CMJ test in boys, with the most mature players demonstrating higher jump height scores (+12%; δ = 0.93). Finally, a significant percentage (>25%) of tennis players, independent of sex, demonstrated bilateral asymmetries in hip ROM, hip strength, and jump height values.

CONCLUSION

The findings of this study show that in U13 and U15 male and female tennis players, there were neither positive nor negative maturity-associated variations in the clinical measurements analyzed (with the exception of jump height in male players). The high proportion of tennis players showing bilateral asymmetries in dynamic balance, hip ROM, and strength and jump performance highlight the need of future studies to analyze these factors in relation to unilateral tennis-specific adaptations in the musculoskeletal and sensorimotor systems.

CLINICAL RELEVANCE

These results may help to better understand how different clinical measurements are associated with the process of growth and maturation in elite youth tennis players and may aid in the design of specific training interventions during these stages of development.

The Effect of Spinal Asymmetries on Physical Fitness Parameters in Young Elite Soccer Players

The purpose of the study was to examine the effect of spinal asymmetries on specific physical fitness parameters in young elite soccer players. Fifty male soccer players, all members of the under 17 (U17) and 15 (U15) National teams of Cyprus, were initially evaluated for thoracic kyphosis, lumbar lordosis and scoliosis asymmetries. Based on the spinal asymmetries’ initial evaluation, soccer players were categorized into the asymmetry group (AG) and normal group (NG) per spinal asymmetry. Hamstring and lower-back flexibility, countermovement jump (CMJ) and lower body isokinetic maximum force were evaluated between AG and NG. CMJ with arm swing was lower in kyphotic posture AG compared with the NG (AG: 41.70 ± 3.59 cm, NG: 44.40 ± 4.34 cm; p = 0.028). Single leg CMJ was lower in both legs in scoliotic posture AG compared with the NG (right: AG: 17.42 ± 1.86 cm, NG: 19.16 ± 2.42 cm, p = 0.008, left: AG: 17.54 ± 1.33 cm, NG: 19.97 ± 2.91 cm; p = 0.002). Sit-and-reach flexibility was lower in scoliotic posture AG (AG: 20.44 ± 5.76 cm, NG: 24.82 ± 6.83 cm; p = 0.024) and higher in lordotic posture AG (AG: 25.95 ± 6.59 cm, NG: 21.73 ± 6.45 cm; p = 0.04) both compared with the NG. No significant difference was found for quadriceps and hamstrings concentric peak torque between the AG and NG (p > 0.05). The current study revealed that kyphotic and scoliotic posture asymmetries deteriorate neuromuscular explosiveness performance and diminish lower limbs’ flexibility in young International-level soccer players.

Morphological and functional asymmetry in elite youth tennis players compared to sex- and age-matched controls

Besides examining upper and lower limb morphological and functional asymmetry magnitudes, this study examined the relationship between lean mass and functional asymmetry in terms of magnitude and direction in 41 youth tennis players versus 41 controls. Asymmetry magnitude was determined using anthropometric measurements (circumferences, widths), bioelectrical impedance analysis (lean mass) and a test battery (handgrip strength, seated medicine ball throw, plate tapping, single leg countermovement jump, single leg forward hop test, 6 m single leg hop test, 505 change of direction). ANOVAs compared the dominant (overall highest/best value) against the non-dominant (highest/best value of opposing limb) result. Linear regressions explored the relationship between lean mass and functional asymmetry magnitudes. Kappa coefficients examined asymmetry direction consistency between the limb displaying the highest lean mass value and the limb performing dominantly across tests. Significant asymmetry magnitudes (p < 0.05) were found for all upper and lower limb outcome measures. No significant relationship was apparent between lean mass and functional asymmetry magnitude (r-value = -0.283-0.262). Despite finding (almost) perfect consistency in asymmetry direction (k-value = 0.84-1.00) for the upper limb, poor to slight consistency (k-value = -0.03-0.15) was found for the lower limb. Therefore, lean mass and functional asymmetry should be examined independently.

Cellular and molecular pathways controlling muscle size in response to exercise

From the discovery of ATP and motor proteins to synaptic neurotransmitters and growth factor control of cell differentiation, skeletal muscle has provided an extreme model system in which to understand aspects of tissue function. Muscle is one of the few tissues that can undergo both increase and decrease in size during everyday life. Muscle size depends on its contractile activity, but the precise cellular and molecular pathway(s) by which the activity stimulus influences muscle size and strength remain unclear. Four correlates of muscle contraction could, in theory, regulate muscle growth: nerve-derived signals, cytoplasmic calcium dynamics, the rate of ATP consumption and physical force. Here, we summarise the evidence for and against each stimulus and what is known or remains unclear concerning their molecular signal transduction pathways and cellular effects. Skeletal muscle can grow in three ways, by generation of new syncytial fibres, addition of nuclei from muscle stem cells to existing fibres or increase in cytoplasmic volume/nucleus. Evidence suggests the latter two processes contribute to exercise-induced growth. Fibre growth requires increase in sarcolemmal surface area and cytoplasmic volume at different rates. It has long been known that high-force exercise is a particularly effective growth stimulus, but how this stimulus is sensed and drives coordinated growth that is appropriately scaled across organelles remains a mystery.

No Relationship between Lean Mass and Functional Asymmetry in High-Level Female Tennis Players

The relationship between lean mass and functional asymmetry in terms of their magnitude and direction was examined in 22 high-level female tennis players (20.9 ± 3.6 years). Lean mass of both upper and lower extremities was examined using Dual X-ray Absorptiometry. Functional asymmetry was assessed using a battery of field tests (handgrip strength, seated shot-put throw, plate tapping, single leg countermovement jump, single leg forward hop test, 6 m single leg hop test, and 505 change of direction (time and deficit)). Paired sample t-tests compared the dominant (overall highest/best (performance) value) against the non-dominant value (highest/best (performance) value of the opposing extremity). Linear regressions were used to explore the relationship between lean mass and functional asymmetry magnitudes. Kappa coefficients were used to examine the consistency in direction between the extremity displaying the highest lean mass value and the extremity performing dominantly across tests. Significant asymmetry magnitudes (p < 0.05) were found for all upper and lower extremity lean mass and functional values. No relationship was apparent between lean mass and functional asymmetry magnitudes (p-value range = 0.131–0.889). Despite finding perfect consistency in asymmetry direction (k-value = 1.00) for the upper extremity, poor to fair consistency (k-value range = −0.00–0.21) was found for the lower extremity. In conclusion, lean mass and functional asymmetries should be examined independently.

Evaluation of the relationship between history of lower back pain and asymmetrical trunk range of motion

BACKGROUND

Low back pain (LBP) is a common complaint and preventive measures should be considered immediately. In addition, asymmetrical trunk motion, which occurs due to repetitive motion upon performing daily activities, may be one of the biomechanical factors to cause LBP.

OBJECTIVE

To investigate the characteristics of asymmetrical trunk motion in women with a history of LBP.

METHODS

Thirty-four women were dichotomously categorized into either the LBP or non-LBP group. Trunk active range of motion (RoM) upon sitting and standing were measured via a three-dimensional motion analysis system. Each RoM and rotation and side-flexion asymmetries were calculated and an unpaired t-tests were used to identify differences between each group.

RESULTS

Trunk rotation asymmetry upon sitting and standing position in LBP group was significantly greater than that in non-LBP group. Furthermore, trunk rotation angle upon sitting in LBP group was significantly larger than that in non-LBP group.

CONCLUSIONS

The limited RoM and asymmetry of trunk rotation may be due to imposed repetitive mechanical stress on habitual excessive motion, including most asymmetrical movements. Our findings indicated that a small trunk rotation angle and asymmetrical trunk rotation may be useful parameters to predict LBP onset or other musculoskeletal conditions of the trunk.

Effects of backhand stroke styles on bone mineral content and density in postmenopausal recreational tennis players: a cross-sectional pilot investigation

Background

One-handed backhand (OB) and two-handed backhand (TB) styles are commonly used in tennis, but only TB generates loadings on the non-dominant arm and a greater extension torque on the rear leg, leading to a greater axial torque involving rotation of the hip and trunk. The current study investigated whether those effects can further affect bone area (BA), bone mineral content (BMC) and density (BMD) in postmenopausal recreational tennis players.

Methods

BA, BMC and BMD of the lumbar spine, hip and distal radius were assessed using dual-energy X-ray absorptiometry in TB, OB, and swimmers’ group as a control (SG) (all participants self-reported for at least 5 years of exercise history, n = 14 per group). Muscular strength was assessed with a hand dynamometer. Among these three groups, the BA, BMC and BMD of distal radius and muscle strength were assessed using one-way ANOVA, and those of the lumbar region and the hip joint were tested by one-way ANCOVA.

Results

TB showed higher BMC and BMD for both lumbar spine and femoral neck than SG (all, p < 0.05). Both OB and TB showed greater BMD inter-trochanter than SG (both, p < 0.05). OB demonstrated greater inter-arm differences in the distal radius, which involved 1/3 distal for BMC and mid-distal radius for BMD compared to the TB and SG (all, p < 0.05). In addition, greater inter-arm asymmetry of grip strength was found in OB compared to TB and SG (both, p < 0.05).

Conclusion

For postmenopausal women, performing two-handed backhand strokes, leads to higher BMC and BMD in the non-dominant arm, the lumbar region, and hips, indicating potential benefit to maintain bone health and strength. Whether this result leads to reducing the risk of osteoporosis needs to be investigated in further research.

International vs. National female tennis players: a comparison of upper and lower extremity functional asymmetries

BACKGROUND

Asymmetries have been reported to negatively impact sport performance. This study examined the magnitude and direction of whole-body functional asymmetry in international versus national female tennis players.

METHODS

Ten internationally and twelve nationally ranked tennis players participated. Upper extremity functional asymmetries (or side-to-side performance differences) were evaluated using handgrip strength, seated shot-put throw and plate tapping. Lower extremity functional asymmetries were determined using the single leg countermovement jump, single leg forward hop test, 6 m single leg hop test, 505 changes of direction (time and deficit), and Y-balance test (anterior, posteromedial, posterolateral). ANOVAs were used to compare the dominant (overall best or fastest result of a specific test) versus non-dominant performance values (best or fastest result of the corresponding extremity) within the internationally versus nationally ranked players. Functional asymmetry magnitudes differences (expressed as a %) were examined using Mann-Whitney U tests. Kappa coefficients examined the consistency as to which extremity performed dominantly across tests.

RESULTS

Significant asymmetries for every upper and lower extremity test were found. The functional asymmetry magnitude was significantly (p=0.020) higher on the single leg forward hop test for the nationally (6.3%) versus internationally ranked players (2.9%). Kappa coefficients showed perfect levels of consistency regarding all upper extremity tests (k=1.00), indicating true limb dominance whereas more variance was found as to which lower extremity performed dominantly across tests (k range=-0.067-0.174).

CONCLUSIONS

The included female tennis players displayed significant whole-body functional asymmetries. Poor consistency as to which lower extremity performed dominantly across tests warrants individual asymmetry monitoring.

Relationship between muscular fitness and bone health in young baseball players

The physical actions developed by baseball players can increase muscular fitness, and consequently improve bone health. The objective was to relate some indicators of muscular fitness to bone health in young baseball players. A descriptive cross-sectional study was carried out in 102 children and adolescent baseball players of the Brazilian National Team. The age range ranged from 9.0 to 15.0 years, the average chronological age was 12.2±2.2 years and the maturity status was 14.8±0.5 APHV (age at peak height velocity). Anthropometry, body composition [% fat, fat mass (FM) and fat-free mass (FFM)], physical tests [horizontal jump (HJ) and medicine ball throw (MBT)] bone health was estimated by anthropometry [bone mineral density (BMD) and bone mineral content (BMC)]. There was positive and significant correlation between bone health with FFM (r2= 89%) and with muscle strength tests (HJ and MBT) (R2= 55 to 75%). Young baseball players classified with low bone health level, reflected decreased values of FFM, HJ and MBT, in relation to young players classified with moderate and high bone health level (p<0.05). It was shown that good bone health is a consequence of a greater presence of muscular fitness, as a result of increased physical activity. These results suggest that emphasis should be placed on those young people who present a greater risk of having low BMD and BMC.

Asymmetry of Muscle Mass Distribution and Grip Strength in Professional Handball Players

Handball is among the disciplines that impose a significant degree of asymmetry on the body movement. The aim of the study is to assess the influence of physical effort on the occurrence of asymmetry in body musculature and in isometric strength of handball players. The study examined 36 professional handball players. Players' height and body mass were measured as to calculate their body mass indexes (BMIs). Segmental bioelectrical impedance analysis (SBIA) was used to assess: the percentage of fat mass, total muscle mass (MM), musculature of the right and left side of the body, and body segments (trunk, upper and lower limbs). Moreover, grip strength was also measured. The assessment confirmed the existence of discrepancies in the right and left sides of players' bodies for the majority of the parameters. Cross-asymmetry and significant bilateral discrepancies in trunk musculature were also observed. Morphological asymmetry may impact performance in sports since it can cause unfavorable functional changes, which in turn increase the risk of injury and conditions caused by overexertion. Therefore, we believe it is important to emphasize the importance of individualized symmetrization during sports practice and consistent monitoring of the asymmetries occurring in different body parts; this should both improve one's sports results and minimize the risk of injury.

Whole-body morphological asymmetries in high-level female tennis players: A cross‑sectional study

This cross-sectional study aimed to examine the degree of whole-body morphological asymmetries in female tennis players. Data were collected in 19 high-level female tennis players (21.3 ± 3.4 years). Based on anthropometric measurements (upper arm, lower arm, wrist, upper leg and lower leg circumferences as well as elbow and knee widths) and dual x-ray absorptiometry research scans (bone mineral density (BMD), bone mineral content (BMC), lean mass (LM), fat mass (FM) as well as humerus, radio-ulnar, femur and tibia bone lengths), within-subject morphological asymmetries for both upper (dominant vs. non-dominant) and lower (contralateral vs. ipsilateral) extremities were examined. Upper arm (p = 0.015), lower arm (p < 0.001) and wrist circumferences (p < 0.001), elbow width (p = 0.049), BMD (p < 0.001), BMC (p < 0.001), LM (p = 0.001), humerus (p = 0.003) and radio-ulnar bone length (p < 0.001) were all greater in the dominant upper extremity. BMC (p < 0.001) and LM (p < 0.001) were greater in the contralateral lower extremity, whereas FM (p = 0.028) was greater in the ipsilateral lower extremity. This is the first study to report significant side-to-side differences in both upper and lower extremities in high-level female tennis players.

Asymmetry of Musculature and Hand Grip Strength in Bodybuilders and Martial Artists

The functional preference for the upper limb influences the occurrence of bilateral differences in other segments of the human body. The aim of the study is to assess the influence of the applied fighting technique and targeted physical effort on the occurrence of asymmetry in body musculature and isometric strength in bodybuilders and competitors of selected martial arts. Academic athletes practicing judo (J), jiu-jitsu (JJ), and bodybuilding (BB) were examined. The control group (C) consisted of students who do not practice any sports. The assessment of the body structure was conducted through segmental bioelectrical impedance analysis. Moreover, the study took into account the measurements of left- and right-hand grip strength. In judo, the uneven physical exertion of the right and left sides of the body further increases both directional and absolute asymmetry. Bilateral asymmetry of musculature in jiu-jitsu competitors and bodybuilders occurs to a lesser extent. The control group was characterized by cross-asymmetry. So as to avoid the risk of injury of sportsmen, it is important to consistently supervise and correct their body structure, which also includes the symmetrical participation of the active muscle mass in particular segments. The symmetrisation process should be individualized since each particular sportsman has their own side-to-side body morphology.

Bone asymmetries in the limbs of children tennis players: testing the combined effects of age, sex, training time, and maturity status

This study estimated upper and lower limb bone mineral content (BMC) and bone area (BA) in 48 children tennis players (24 boys, 24 girls) aged 7-13 years. The sample comprised four age groups (8.2 ± 0.44, 9.5 ± 0.13, 10.5 ± 0.33, 12.2 ± 0.58). BMC and BA were measured via DXA, and sexual maturity by the Tanner scale, then used as a binary: prepubertal vs peripubertal. Total training time (TTT) included all playing years. Arms were asymmetric and legs symmetric. Boys were more asymmetric than girls in BMC (18% vs 13%) and BA (11% vs 8%). Pre-pubertal children were less asymmetric than peri-pubertal in BMC (14% vs 18%) and in BA (9.4% vs 10%). Bone growth changed with age and TTT markedly better in the dominant arm. The linear combination of TTT, sex, and maturity binary extracted 59% of BMC asymmetry and only 21% of BA asymmetry. For both bone parameters the sex effect was significant only for the pre-pubertal children. Training time constitutes the best predictor of bone asymmetry compared to age, sex, and maturity; when adequate, playing arm bone hypertrophy may be detectable at the age of 7-8 years. These results have health and performance implications.

Influence of typical handball characteristics on upper body posture and postural control in male handball players

Background

Well defined constitutional parameters support the physical fatigue resistance in handball to maintain the performance level for the majority of actions. Ideal constitutional conditions are necessary to achieve these physiological advantages in handball. But limited knowledge exists about the upper body posture or the postural control in correlation to the Body Mass Index (BMI), playing years, playing position and throwing arm in professional male handball.

Methods

Ninety-one male handball players participate (24.1 ± 5.9 years; playing experience 16.6 ± 5.7 years). A three-dimensional back scanner and a pressure measuring plate were used.

Results

Correlations between BMI and upper body posture and postural control were not significant. Same counts for the comparison between the left and right throwing arm according to upper body posture and postural control (p ≥ 0.05). Correlations between the years of playing can be found at pelvis height (p ≤ 0.04) and for the length of the Center of Pressure (CoP) (p ≤ 0.01). Wing players are 6.5-8.5 cm smaller. The playing position is independently of BMI, age or upper body posture (p ≥ 0.05). Backcourt players have a higher load of the left and a lower load of the right foot compared to wing players (p ≤ 0.001). Left-right comparison (p ≤ 0.001/ 0.01) can be seen in pivot player (covered area), backcourt player (weight distribution left/right [rear] foot), wing player (weight and force distribution left/right foot, covered area).

Conclusion

Goalkeeper, Backcourt and pivot players are taller and heavier than wing players. These physiological demands are not detectable in the upper body posture and slightly in postural control. Wing players have the most asymmetric load distribution and the longest length of CoP. Since goalkeepers do not differ from pivot or backcourt players, this can be lead back to the same training.

Impact of changes in fat mass and lean soft tissue on bone mineral density accrual in adolescents engaged in different sports: ABCD Growth Study

Body composition can have a significant impact on bone mineral density (BMD) in pediatric patients and may cause bone disease. This study demonstrated that lean soft tissue (LST) seems to have a greater impact on BMD gain in the lower limbs of adolescents.

PURPOSE

To analyze the impact of changes in lean soft tissue (LST) and fat mass on areal bone mineral density (BMD) accrual in the lower limbs among adolescents engaged in sports with different weight-bearing levels.

METHODS

Longitudinal (12 months: measurements at two time points). Adolescents of both sexes (n = 191; 62 girls [32.5%] and 129 boys [67.5%]) were divided into three groups: control group (n = 65), swimming group (n = 25), and weight-bearing sports group (n = 100). Absolute changes in LST (kg) and fat mass (kg) were the independent variables, while BMD accrual (left and right legs) was the dependent variable. Linear regression was used to assess the relationship between dependent and independent variables in a multivariate model adjusted by sex, body weight, somatic maturation, serum osteocalcin, and baseline values of BMD of the lower limbs.

RESULTS

For the left leg, LST was positively related to areal BMD accrual in the control (β = 0.021 [95%CI: 0.001 to 0.042]) and weight-bearing sport groups (β = 0.051 [95%CI: 0.037 to 0.065]), but not among swimmers (β = 0.029 [95%CI: - 0.004 to 0.062]). For the right leg, LST was positively related to areal BMD accrual in the swimming group (β = 0.065 [95%CI: 0.031 to 0.100]) and weight-bearing sport groups (β = 0.048 [95%CI: 0.034 to 0.062]), but not in the control group (β = 0.014 [95%CI: - 0.002 to 0.030]). Fat mass was not significantly related to areal BMD in either leg.

CONCLUSIONS

Changes in LST were the most relevant determinant of BMD accrual in the lower limbs, mainly among adolescents engaged in sports.

Anthropometric, Body Composition, and Morphological Lower Limb Asymmetries in Elite Soccer Players: A Prospective Cohort Study

The aim of this study was to identify and compare parameters related to anthropometry, body composition (BC), and morphological asymmetry in elite soccer players in nine age categories at the same soccer club (n = 355). We used a bio-impedance analyzer to measure the following indicators of BC: body height (BH); body mass (BM); relative fat-free mass (FFMr); percentage of fat mass (FM); and bilateral muscle mass differences in the lower extremities (BLD∆). Age showed a significant influence on all parameters observed (F_64,1962 = 9.99, p = 0.00, λ = 14.75, η²_p = 0.25). Adolescent players (from U16 through adults) had lower FM values (<10%) compared to players in the U12-U15 categories (>10%). The highest FFMr was observed in the U18 category. Players in the U12 and U13 categories showed more homogenous values compared to older players. With increasing age, significantly higher FFMr was observed in the lower extremities. An inter-limb comparison of the lower extremities showed significant differences in the U17 category (t₂₇ = 2.77, p = 0.01) and in adult players (t₆₈ = 5.02, p = 0.00). Our results suggest that the end of height growth occurs around the age of 16 years, while weight continues to increase until 20 years. This increase is not linked to decreasing FM, nor to the FFMr, which remains stable. We found morphological asymmetries between limbs in players of the U17 category and in adult players.

Lumbar bone mineral asymmetry in elite cricket fast bowlers

PURPOSE

Bone responds to mechanical loading by increasing bone mineral density (BMD) and/or bone area to enhance bone strength at the site of the greatest strain. Such localised adaptation has not been demonstrated at the spine. The aim of this study is to determine if BMD and/or bone mineral content (BMC) differs between dominant (ipsilateral to bowling/throwing arm) and non-dominant sides of the vertebrae in cricket fast bowlers, and whether this asymmetry differs according to stress fracture or disc injury history. A further aim was to determine if regional BMD and BMC in the lumbar spine differ between fast bowlers, other cricketers, rugby players and non-active controls, to highlight the site-specific response of lumbar vertebra to unilateral activity.

METHODS

23 fast bowlers, 14 other cricketers, 22 rugby players and 20 controls underwent an antero-posterior (AP) and lateral DXA scans of their lumbar spine to assess BMD, BMC and area. A custom analysis measured BMD and BMC of the dominant and non-dominant sides (lateral 33%) of the AP lumbar spine. BMD and BMC were compared between groups, injury status, vertebrae and sides using ANOVA.

RESULTS

Analysis of medical records showed that 6 fast bowlers had a history of lumbar stress fracture. Significantly greater BMD and BMC was found in the L4 non-dominant vertebra compared with the dominant vertebra in fast bowlers. BMD and BMC differed significantly according to vertebra, side and group, with fast bowlers having significantly greater BMD and BMC at the L3 and L4 non-dominant vertebra compared with other groups (L3: 13.3%-45.3%, L4: 15.7%-44.0%) compared with other groups. Fast bowlers who never suffered lumbar stress fracture had 3.6% and 1.7% greater BMD in the dominant and non-dominant sides of lumbar vertebrae respectively compared with those who did suffer lumbar stress fracture, but evidence of this was weaker (P = 0.08).

CONCLUSION

The lumbar spine responds to a unique unilateral high loading activity through site-specific increased bone mass at the site of most strain. Fast bowlers had increased lumbar BMD, particularly on the non-dominant side of L4, although this adaptation was less marked in those with history of lumbar stress fracture. Site-specific low bone mineral density within the lumbar side may be implicated in the aetiology of lumbar stress fracture.

Mechanoregulation of Bone Remodeling and Healing as Inspiration for Self-Repair in Materials

The material bone has attracted the attention of material scientists due to its fracture resistance and ability to self-repair. A mechanoregulated exchange of damaged bone using newly synthesized material avoids the accumulation of fatigue damage. This remodeling process is also the basis for structural adaptation to common loading conditions, thereby reducing the probability of material failure. In the case of fracture, an initial step of tissue formation is followed by a mechanobiological controlled restoration of the pre-fracture state. The present perspective focuses on these mechanobiological aspects of bone remodeling and healing. Specifically, the role of the control function is considered, which describes mechanoregulation as a link between mechanical stimulation and the local response of the material through changes in structure or material properties. Mechanical forces propagate over large distances leading to a complex non-local feedback between mechanical stimulation and material response. To better understand such phenomena, computer models are often employed. As expected from control theory, negative and positive feedback loops lead to entirely different time evolutions, corresponding to stable and unstable states of the material system. After some background information about bone remodeling and healing, we describe a few representative models, the corresponding control functions, and their consequences. The results are then discussed with respect to the potential design of synthetic materials with specific self-repair properties.

Sports participation and muscle mass affect sex-related differences in bone mineral density between male and female adolescents: A longitudinal study

BACKGROUND

Sports participation plays an important role in bone gain during childhood and adolescence. The aim here was to identify sex-related determinants of bone mineral density (BMD) differences between male and female adolescents, with emphasis on the role of sports participation.

DESIGN AND SETTING

Longitudinal study conducted in a public university in Presidente Prudente, Brazil.

METHODS

The sample comprised 48 adolescents aged 11-17 years, of both sexes, who were matched according to sex, age and sports participation. BMD was the main outcome, while muscle mass, sports participation, calendar age and biological maturation were treated as covariates. Participants were followed up after nine months.

RESULTS

At baseline, BMD values were similar between the sexes. However, adjustment for covariates showed that BMD was higher among girls at all sites, with a contribution from lean soft tissue (LST) in the model (partial eta-squared, ES-r = 0.619 in upper limbs; 0.643 in lower limbs; 0.699 in spine; and 0.599 in whole body). Sports participation only explained the upper-limb variance (ES-r = 0.99). At the follow-up, the results resembled the baseline except in the lower limbs (P = 0.109), in which BMD was similar between the groups. BMD gain over time was similar between girls and boys in all segments, and baseline LST affected upper-limb and whole-body BMD accrual (ES-r = 0.396 and 0.107, respectively).

CONCLUSION

Whole-body and specific-site BMD differed between baseline and follow-up. However,BMD accrual was similar between the sexes, given that muscle mass constituted the most relevant determinant of the difference between them.

Morphological and Isokinetic Strength Differences: Bilateral and Ipsilateral Variation by Different Sport Activity

BACKGROUND

The purpose of this study was to investigate the morphological and isokinetic strength asymmetry and magnitude in young athletes.

METHODS

One hundred and thirty nine male subjects (soccer, floorball, non-athletes) were measured for proportion of muscle mass between upper extremities (BADΔ) and lower extremities (BLDΔ). Moreover, the peak muscle torque of knee extensors (PTE) and flexors (PTF), ipsilateral (H:Q) and bilateral strength ratio (Q:Q, H:H) were measured.

RESULTS

We found significant differences in observed parameters with respect to different sport activities (F = 13.02, p = 0.00, η p 2 = 0.80). Higher values of BADΔ were observed in the non-active (0.19 ± 0.11 kg) group compared with soccer players (0.10 ± 0.11 kg). We found a lower value of BLDΔ in floorball players (0.32 ± 0.11 kg) compared with soccer players (0.58 ± 0.27 kg) and non-active boys (0.63 ± 0.28 kg). Results revealed significantly higher PTE in soccer players compared with non-active boys and floorball players and higher Q:Q ratio in soccer players (10.99 ± 7.75%) compared with non-active boys (7.47 ± 5.92%).

CONCLUSIONS

This study revealed that there are morphological and strength asymmetries in the observed groups, which may have potential maladaptive effects (e.g. uncompensated overload of extremity) in athletes affected by specific load.

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.

Health Effects of Wrist-Loading Sports During Youth: A Systematic Literature Review

BACKGROUND

The benefits and risks of performing popular wrist-loading sports at a young age have not been investigated systematically. We aimed to evaluate positive and negative long-term wrist-related health effects of sports performance requiring repetitive wrist loading during youth.

METHODS

Six databases were searched for cohort and cross-sectional studies. Three investigators selected studies evaluating quantitatively measured health effects of upper extremities in athletes practicing wrist-loading sports (gymnastics, tennis, volleyball, field hockey, rowing, and judo) for minimally 4 months before the age of 18.

RESULTS

A total of 23 studies with 5 outcome measures, nearly all of moderate to good quality, were eligible for inclusion. Bone mineral density and bone mineral content were higher in athletes compared with controls and in tennis players' dominant arm. Mixed results were found for ulnar variance in gymnasts. Handgrip strength was greater in tennis players' dominant arm and in experienced gymnasts.

CONCLUSIONS

Wrist-loading sports performance during youth can promote bone strength in wrists and dominant handgrip strength, but evidence on the lasting of these effects and on prevalence of wrist joint degeneration in former young athletes is limited. For better counseling of young athletes and their parents, future studies with increased comparability are essential, for which recommendations are provided.

Adults Engaged in Sports in Early Life Have Higher Bone Mass Than Their Inactive Peers

Purpose: To analyze the relationship between engagement in sports in early life and bone variables among adults of both sexes. Methods: The sample was composed of 225 men and women. Demographic data were collected, and dual-energy X-ray absorptiometry was used to assess bone mineral density, bone mineral content, and lean soft tissue. Sports participation in early life was assessed by an interview including childhood and adolescence. Consumption of tobacco and alcohol was also assessed by interview and the habitual physical activity level by a pedometer. Results: Inactive men had bone mineral content around 11% lower than active men in childhood or adolescence, whereas for women, this difference represented around 14%. Active men had 74% less fat mass than inactive men in early life, and the difference was 67% for women. Early sports participation explained the differences in whole-body bone mineral content (16.8%, P-value = .005) and bone mineral density (8.8%, P-value = .015), as well as bone mineral density in lower limbs (18.9%, P-value = .001) among women. Conclusion: Adults engaged in sports in early life have higher bone mass than their inactive peers, especially women.

Muscle-Bone Crosstalk: Emerging Opportunities for Novel Therapeutic Approaches to Treat Musculoskeletal Pathologies

Osteoporosis and sarcopenia are age-related musculoskeletal pathologies that often develop in parallel. Osteoporosis is characterized by a reduced bone mass and an increased fracture risk. Sarcopenia describes muscle wasting with an increasing risk of injuries due to falls. The medical treatment of both diseases costs billions in health care per year. With the impact on public health and economy, and considering the increasing life expectancy of populations, more efficient treatment regimens are sought. The biomechanical interaction between both tissues with muscle acting on bone is well established. Recently, both tissues were also determined as secretory endocrine organs affecting the function of one another. New exciting discoveries on this front are made each year, with novel signaling molecules being discovered and potential controversies being described. While this review does not claim completeness, it will summarize the current knowledge on both the biomechanical and the biochemical link between muscle and bone. The review will highlight the known secreted molecules by both tissues affecting the other and finish with an outlook on novel therapeutics that could emerge from these discoveries.

Somatic maturation and the relationship between bone mineral variables and types of sports among adolescents: cross-sectional study

CONTEXT AND OBJECTIVE:

Peak height velocity (PHV) is an important maturational event during adolescence that affects skeleton size. The objective here was to compare bone variables in adolescents who practiced different types of sports, and to identify whether differences in bone variables attributed to sports practice were dependent on somatic maturation status.

DESIGN AND SETTING:

Cross-sectional study, São Paulo State University (UNESP).

METHODS:

The study was composed of 93 adolescents (12 to 16.5 years old), divided into three groups: no-sport group (n = 42), soccer/basketball group (n = 26) and swimming group (n = 25). Bone mineral density and content were measured using dual-energy x-ray absorptiometry and somatic maturation was estimated through using peak height velocity. Data on training load were provided by the coaches.

RESULTS:

Adolescents whose PHV occurred at an older age presented higher bone mineral density in their upper limbs (P = 0.018). After adjustments for confounders, such as somatic maturation, the swimmers presented lower values for bone mineral density in their lower limbs, spine and whole body. Only the bone mineral density in the upper limbs was similar between the groups. There was a negative relationship between whole-body bone mineral content and the weekly training hours (β: -1563.967; 95% confidence interval, CI: -2916.484 to -211.450).

CONCLUSION:

The differences in bone variables attributed to sport practice occurred independently of maturation, while high training load in situations of hypogravity seemed to be related to lower bone mass in swimmers.

Basketball Affects Bone Mineral Density Accrual in Boys More Than Swimming and Other Impact Sports: 9-mo Follow-Up

The objective of this study was to analyze the effect of different sports on bone mineral density (BMD) accrual among male adolescents during a 9-mo follow-up. The sample was composed of 82 boys (control [n = 13], basketball [n = 14], karate [n = 9], soccer [n = 18], judo [n = 12], and swimming [n = 16]) who were followed up for 9 mo (from October 2013 to August 2014). BMD (gram per square centimeter) was assessed at baseline and follow-up using a dual-energy X-ray absorptiometry scanner, whereas somatic maturation was estimated through the use of the peak height velocity. Vitamin D consumption was assessed by questionnaire. After 9 mo of follow-up, all groups (including the control group) presented significant BMD accrual (overall sample: 4.5% in the whole body). On the other hand, the basketball group presented higher BMD accrual in the upper limbs (17.6%) than the control group (7.2%). A similar difference was observed in whole-body BMD (control group: 4.1% vs basketball group: 7.1%). The basketball group had significantly higher BMD gains than the control group and other sports groups.

Bilateral Asymmetry of Radius and Tibia Bone Macroarchitecture and Microarchitecture: A High-Resolution Peripheral Quantitative Computed Tomography Study

Studies assessing bone health often select the dominant or nondominant limb to scan, but not both, for efficiency reasons. New scanning technology allows 3-dimensional (3D) visualization of the microarchitecture in bone, but it is not well understood whether there are differences between the dominant and nondominant limbs. Using 3D high-resolution peripheral quantitative computed tomography (HR-pQCT), the aim of this study is to investigate the effect of limb dominance on bone macroarchitecture and microarchitecture. Healthy male and female participants (N=100; 59 female, 41 male), mean age 30.7±12.1 years, were scanned at both radii and tibiae using HR-pQCT. Hand and foot dominance were determined by the participant's self-report. Most participants were right hand dominant (94.0%) and right foot dominant (91.0%). In the pooled cohort, the dominant radius had significantly greater cortical area (2.11%; p=0.002) and failure load (3.00%; p=0.001). At the tibia, the dominant foot had significantly lower bone mineral density (-0.77%; p=0.042), cortical area (-1.05%; p=0.031), and thickness (-1.51%; p=0.017). For females, there were no differences at the radius, but at the tibia, the dominant side had greater cross-sectional area (1.03%; p=0.044). Our data suggest that dominance has a small yet significant effect on macroarchitecture at both the ultradistal radius and tibia but not microarchitecture. This work emphasizes that it is important to be consistent in the selection of either dominant or nondominant limbs for HR-pQCT cohort studies; however, in the case where the opposite limb needs to be scanned, there would be small differences in macroarchitecture and no significant differences in microarchitecture anticipated.

[Practice of martial arts and bone mineral density in adolescents of both sexes]

OBJECTIVE

The purpose of this study was to analyze the relationship between martial arts practice (judo, karate and kung-fu) and bone mineral density in adolescents.

METHODS

The study was composed of 138 (48 martial arts practitioners and 90 non-practitioners) adolescents of both sexes, with an average age of 12.6 years. Bone mineral density was measured using Dual-Energy X-ray Absorptiometry in arms, legs, spine, trunk, pelvis and total. Weekly training load and previous time of engagement in the sport modality were reported by the coach. Partial correlation tested the association between weekly training load and bone mineral density, controlled by sex, chronological age, previous practice and somatic maturation. Analysis of covariance was used to compare bone mineral density values according to control and martial arts groups, controlled by sex, chronological age, previous practice and somatic maturation. Significant relationships between bone mineral density and muscle mass were inserted into a multivariate model and the slopes of the models were compared using the Student t test (control versus martial art).

RESULTS

Adolescents engaged in judo practice presented higher values of bone mineral density than the control individuals (p-value=0.042; Medium Effect size [Eta-squared=0.063]), while the relationship between quantity of weekly training and bone mineral density was significant among adolescents engaged in judo (arms [r=0.308] and legs [r=0.223]) and kung-fu (arms [r=0.248] and spine [r=0.228]).

CONCLUSIONS

Different modalities of martial arts are related to higher bone mineral density in different body regions among adolescents.

Divergence in male and female manipulative behaviors with the intensification of metallurgy in Central Europe

Humeral morphology has been shown to reflect, in part, habitual manipulative behaviors in humans. Among Central European agricultural populations, long-term social change, increasing task specialization, and technological innovation all had the potential to impact patterns of habitual activity and upper limb asymmetry. However, systematic temporal change in the skeletal morphology of agricultural populations in this region has not been well-characterized. This study investigates diachronic patterns in humeral biomechanical properties and lengths among 174 adult Central European agriculturalists through the first ∼ 5400 years of farming in the region. Greater asymmetry in biomechanical properties was expected to accompany the introduction of metallurgy, particularly in males, while upper limb loading patterns were expected to be more similar between the Bronze and Iron Ages. Results revealed a divergence in the lateralization of upper limb biomechanical properties by sex between the Early/Middle Neolithic and Early/Middle Bronze Age. Neolithic females had significantly more variable properties than males in both humeri, while Bronze Age female properties became homogeneous and very symmetrical relative to the right-biased lateralization of contemporaneous males. The Bronze Age to Iron Age transition was associated with morphological change among females, with a significant increase in right-biased asymmetry and a concomitant reduction in sexual dimorphism. Relative to biomechanical properties, humeral length variation and asymmetry were low though some significant sexual dimorphism and temporal change was found. It was among females that the lateralization of humeral biomechanical properties, and variation within them, changed most profoundly through time. This suggests that the introduction of the ard and plow, metallurgical innovation, task specialization, and socioeconomic change through ∼ 5400 years of agriculture impacted upper limb loading in Central European women to a greater extent than men.

Fitness testing of tennis players: how valuable is it?

In tennis, sport-specific technical skills are predominant factors, although a complex profile of physical performance factors is also required. The fitness test batteries assist in examining tennis players' capabilities for performance at different levels in the laboratory as well as in the field, in the junior or elite level. While laboratory tests can be, and are, used to evaluate basic performance characteristics of athletes in most individual sports, in a more specific approach, field-based methods are better suited to the demands of complex intermittent sports like tennis. A regular test battery performed at different periods of the year allows to obtain an individual's performance profile, as well as the ability to prescribe individual training interventions. Thus, the aim of the present review was to describe and evaluate the different physical tests recommended and used by practitioners, sports scientists and institutions (national tennis federations).

Does lean tissue mass accrual during adolescence influence bone structural strength at the proximal femur in young adulthood?

The purpose of this study was to identify whether young adult bone structural strength at the hip is associated with adolescent lean tissue mass (LTM) accrual. It was observed that those individuals who accrued more LTM from adolescence to adulthood had significantly greater adult bone structural strength at the hip.

INTRODUCTION

The purpose of this study was to identify whether young adult bone cross-sectional area (CSA), section modulus (Z), and outer diameter (OD) at the hip were associated with adolescent LTM accrual.

METHODS

One hundred three young adult participants (55 males, 48 females) were tertiled into adolescent LTM accrual groupings. LTM accrual was assessed by serial measures using dual energy X-ray absorptiometry (DXA) from adolescence to young adulthood (21.3 ± 1.3 years). CSA, Z, and OD at the narrow neck (NN) and femoral shaft (S) sites of the proximal femur were assessed in young adulthood (21.3 ± 4.5 years), using hip structural analysis. Group differences were assessed using an analysis of covariance, controlling for adult height, weight, sex, and physical activity levels.

RESULTS

It was found that individuals with higher adjusted adolescent LTM accrual had significantly greater adult adjusted values of NNCSA (2.49 ± 0.06 vs 2.77 ± 0.07 cm(2)), NN Z (1.18 ± 0.04 vs 1.37 ± 0.04 cm(3)), NN OD (3.07 ± 0.04 vs 3.21 ± 0.04 cm), SCSA (3.45 ± 0.08 vs 3.88 ± 0.09 cm(3)), and SZ (1.77 ± 0.05 vs 2.00 ± 0.05 cm(3)) than individuals with lower LTM accrual (p < 0.05).

CONCLUSIONS

These findings suggest that the amount of LTM accrued from adolescence to young adulthood has a positive influence on adult bone structural strength at the proximal femur.

Side-to-side differences in the lower leg muscle-bone unit in male soccer players

PURPOSE

To characterize side-to-side differences in the lower leg muscle-bone unit between the nondominant leg (NL) and the dominant leg (DL) using maximum voluntary forefoot ground reaction force (Fm1LH) during multiple one-legged hopping (m1LH) and tibial bone mass and geometry measured by peripheral quantitative computed tomography (pQCT).

METHODS

Sixty-six male high-level soccer players (age range = 12-18 yr) performed m1LH to determine Fm1LH acting on the forefoot during landing for the NL and DL separately. pQCT scans were obtained to assess bone structural variables at 4%, 14%, 38%, and 66% tibia length and calf muscle cross-sectional area at the 66% site.

RESULTS

First, participants displayed significant (P < 0.05) side-to-side differences in bone mass and geometry at 4%, 14%, and 38% (but not at the 66% site) of tibia length, with higher values in NL relative to DL (+0.7% to +5.6%), most evident at the 14% site. Second, no asymmetries were found for Fm1LH between the two legs (P = 0.442). Third, the relationship between Fm1LH and vBMC 14% was strong for both NL and DL (R2 = 0.48 and R = 0.54, respectively), but side-to-side differences in Fm1LH (ΔFm1LH) and side-to-side differences in vBMC 14% (ΔvBMC 14%) were not related (R2 = 0.04).

CONCLUSIONS

Contrary to expectations from the mechanostat theory, ΔFm1LH and ΔvBMC 14% did not differ in proportion to each other. It seems that playing soccer is a well-balanced activity with respect to Fm1LH. However, the NL contributes to the supporting of the action of the DL, meaning that the loading experienced by the tibia might be more pronounced for the NL relative to the DL, leading to the observed higher bone strength values for the NL.

Effect of vitamin D replacement on hip structural geometry in adolescents: a randomized controlled trial

BACKGROUND

We have shown in a randomized controlled trial that vitamin D increases bone mass, lean mass and bone area in adolescent girls, but not boys. These increments may translate into improvements in bone geometry and therefore bone strength. This study investigated the impact of vitamin D on hip geometric dimensions from DXA-derived hip structural analyses in adolescents who participated in the trial.

METHODS

167 girls (mean age 13.1 years) and 171 boys (mean age 12.7 years) were randomly assigned to receive weekly placebo oil or vitamin D3, at doses of 1400 IU or 14,000 IU, in a double blind placebo-controlled 1-year trial. DXA images were obtained at baseline and one year, and hip images were analyzed using the hip structural analysis (HSA) software to derive parameters of bone geometry. These include outer diameter (OD), cross sectional area (CSA), section modulus (Z), and buckling ratio (BR) at the narrow neck (NN), intertrochanteric (IT), and shaft (S) regions. Analysis of Covariance (ANCOVA) was used to examine group differences for changes of bone structural parameters.

RESULTS

In the overall group of girls, vitamin D supplementation increased aBMD (7.9% and 6.8% in low and high doses, versus 4.2% in placebo) and reduced the BR of NN (6.1% and 2.4% in low and high doses, versus 1.9% in placebo). It also improved aBMD (7.9% and 5.2% versus 3.6%) and CSA (7.5% and 5.1% versus 4.1%) of the IT and OD of the S (2.4% and 2.5% versus 0.8% respectively). Significant changes in the OD and BR of the NN, in the overall group of girls remained, after adjusting for lean mass, and were unaffected with further adjustments for lifestyle, pubertal status, and height measures. Conversely, boys did not exhibit any significant changes in any parameters of interest. A dose effect was not detected and subgroup analyses revealed no beneficial effect of vitamin D by pubertal stage.

CONCLUSIONS

Vitamin D supplementation improved bone mass and several DXA-derived structural bone parameters, in adolescent girls, but not boys. This occurred at a critical site, the femoral neck, and if maintained through adulthood could improve bone strength and lower the risk of hip fractures.

Site-specific variance in radius and tibia bone strength as determined by muscle size and body mass

PURPOSE

To investigate the predictive ability of muscle cross-sectional area (MCSA) and body mass on bone mineral content, compressive bone strength index (BSIc), and the polar stress-strain index (SSIp) of the forearms and lower legs of middle-aged adults.

METHODS

A total of 53 healthy adults (37 male, 16 female; mean age 50.4; SD 2.1 y) were scanned with peripheral quantitative computed tomography (pQCT) to measure radius and tibia total and cortical bone mineral content, BSIc, SSIp, and forearm and lower-leg MCSA (BSIc: 4% distal; SSIp and MCSA at 65% and 66% radius and tibia shaft sites, respectively). Multiple regression models adjusted for sex and height were used to assess the relative variance in radius or tibia bone outcomes predicted by body mass and/or forearm or lower-leg MCSA.

RESULTS

Forearm MCSA independently predicted total bone-mineral content, BSIc, and SSIp in radius (r partial=0.59, 0.56, 0.42). Body mass was a negative predictor of radius BSIc (r partial=-0.32) and did not predict other radius outcomes when both body mass and MCSA were forced in the models. In the lower leg shaft, MCSA, and body mass predicted bone content and strength similarly when independently added to the models with sex and height.

CONCLUSIONS

Forearm MCSA was a dominant predictor of radius bone content and estimated strength. In the tibia, both body mass and lower-leg MCSA contributed to predicting bone content and estimated strength.

Bone mineral density of adolescent female tennis players and nontennis players

The purpose of this study was to determine differences in bone mineral density (BMD) among adolescent female tennis players (TPs) and nontennis players (NTPs) and to assess body composition as a predictor variable of BMD. Nineteen female TPs and 19 female NTPs, ages 14 to 18 years, participated in this study. Lumbar spine, total hip, femoral neck, forearms BMD, and body composition were assessed using dual-energy X-ray absorptiometry (DXA). Lumbar spine and total hip BMD measurements for TP were greater than NTP. However, these differences were not statistically significant (P = 0.37 and 0.12, resp.). TP had significantly greater femoral neck BMD than NTPs (P = 0.02). This difference might play an important role in preventing osteoporosis and decreasing the risk of fractures at the hip later in life.