Estrogen and bone-muscle strength and mass relationships

Bone Remodelling, Vitamin D Status, and Lifestyle Factors in Spanish Vegans, Lacto-Ovo Vegetarians, and Omnivores

Sustainable healthy diets are promoted, and consequently vegetarian diets are currently increasing. However, scientific information on their effects on bone health is scarce. A cross-sectional study was performed in adults (66% women) classified into three groups: omnivores (n = 93), lacto-ovo vegetarians (n = 96), and vegans (n = 112). Nutrient intake, body composition, physical activity, vitamin D status (25-hydroxycholecalciferol, 25-OHD), parathormone (PTH), and bone formation (bone alkaline phosphatase, BAP) and resorption (N-telopeptides of type I collagen, NTx) markers were determined. Lacto-ovo vegetarians and especially vegans showed lower protein, fat, calcium, phosphorous, vitamin D, retinol, iodine, and zinc intakes, and higher carbohydrate, fibre, carotenes, magnesium, and vitamin K intakes compared to omnivores. Body composition was similar in the three groups that performed vigorous physical activity regularly. Body bone mass and muscle mass were positively correlated with BAP, and time performing physical activity with 25-OHD. The prevalence of vitamin D deficiency or insufficiency (25-OHD < 75 nmol/L) was 93.7% in the studied population, and vitamin D deficiency (25-OHD < 25 nmol/L) was significantly higher in vegans. Vegetarians of both groups had increased PTH and NTx with vegans showing significantly higher PTH and NTx than omnivores. Conclusion: Adult vegetarians, especially vegans, should reduce the risk of bone loss by appropriate diet planning and vitamin D supplementation.

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.

Factors associated with osteoarthritis in menopausal women: A registry study of osteoporosis sarcopenia and osteoarthritis

Background

Bone and muscle mass decline after menopause. The risk of osteoarthritis (OA), sarcopenia, and osteoporosis increases in later life. Our objective aimed to assess the possible factors affecting osteoarthritis in menopausal women.

Methods

This is a registry study of osteoporosis, sarcopenia, and osteoarthritis. All subjects accepted bone mineral density (BMD) and body composition studies, and X-rays of both knees were performed. A medical history was taken and biochemical data were recorded. Logistic regression analyses were used to examine the associations between the presence of osteoarthritis and BMD, muscle mass, and other parameters.

Results

A total of 139 patients were enrolled. The mean age of the patients was 73.86 ± 5.83 years in the osteoarthritis group and 74.53 ± 9.90 in the non-osteoarthritis group (p = 0.663). The mean body mass index (BMI) was 24.36 ± 3.64 kg/m2 in the osteoarthritis group, compared with 23.78 ± 3.61 in the non-osteoarthritis group (p = 0.366). The lumbar spine T score was -2.06 ± 1.33 g/cm2 in the osteoarthritis group, and -1.25 ± 1.76 in the non-osteoarthritis group (p = 0.006). There were no significant differences in smoking, alcohol consumption, diabetes, hypertension, cardiovascular disease, neurological disease, and chronic kidney disease between the two groups. When we used osteoarthritis as the outcome, we found that the lumbar spine T score had a significant association with osteoarthritis, with a high T score associated with less osteoarthritis formation (p = 0.024, odds ratio (95% confidence interval) 0.06 (0-0.69)).

Conclusions

Knee osteoarthritis was associated with lumbar spine bone density. This study provides the initial information required to develop clinical algorithms for the early identification of potential high-risk populations, as well as essential information for the development of policies for the detection and prevention of osteoarthritis in menopausal women.

Protein intake and bone health: an umbrella review of systematic reviews for the evidence-based guideline of the German Nutrition Society

This umbrella review aimed at assessing whether a protein intake exceeding the current recommendation for younger (0.8 g/kg body weight [BW]/day) and older (1.0 g/kg BW/day) adults affects bone mineral density and fracture risk. Moreover, the effect of animal or plant protein was evaluated. A systematic literature search was conducted in PubMed, Embase, and Cochrane Database of Systematic Reviews for systematic reviews (SRs) with or without meta-analysis of prospective studies published between 11/2008 and 08/2021. Methodological quality, outcome-specific certainty of evidence, and overall certainty of evidence of the retrieved SRs were assessed using established tools and predefined criteria. Eleven SRs of randomized controlled trials (RCTs) and/or cohort studies were included. In SRs of cohort studies and RCTs, protein intake/kg BW/day ranged between 0.21-0.95 g (low intake) and > 1.24 g (high intake), respectively, and between 0.67-1.1 g (control groups) and 1.01-1.69 g (intervention groups), respectively. The vast majority of outcome-specific certainty of evidence was rated "low" or "very low." The overall certainty of evidence for an association (cohort studies) or effect (RCTs) of total, animal or plant protein intake on each of the investigated outcomes was rated "insufficient," with the exception of possible evidence for a reduced hip fracture risk by high vs. low protein intake. Since protein intakes in low/control and high/intervention groups were very heterogeneous and with low certainty of evidence, it remains unclear whether a dose above the current recommendation or type of protein intake (animal or plant protein) affects bone health overall. However, there is possible evidence for reduced hip fracture risk with high versus low protein intake.

Between-Subject and Within-Subject Variaton of Muscle Atrophy and Bone Loss in Response to Experimental Bed Rest

To improve quantification of individual responses to bed rest interventions, we analyzed peripheral quantitative computer tomography (pQCT) datasets of the lower leg of 76 participants, who took part in eight different bed rest studies. A newly developed statistical approach differentiated measurement uncertainty U_Meas from between-subject-variation (BSV) and within-subject variation (WSV). The results showed that U_Meas decreased 59.3% to 80% over the two decades of bed rest studies (p < 0.01), and that it was higher for muscles than for bones. The reduction of U_Meas could be explained by improved measurement procedures as well as a higher standardization. The vast majority (82.6%) of the individual responses pc_i exceeded the 95% confidence interval defined by U_Meas, indicating significant and substantial BSV, which was greater for bones than for muscles, especially at the epiphyseal measurement sites. Non-significant to small positive inter-site correlations between bone sites, but very large positive inter-site correlation between muscle sites suggests that substantial WSV exists in the tibia bone, but much less so in the calf musculature. Furthermore, endocortical circumference, an indicator of the individual’s bone geometry could partly explain WSV and BSV. These results demonstrate the existence of substantial BSV bone, and that it is partly driven by WSV, and likely also by physical activity and dietary habits prior to bed rest. In addition, genetic and epigenetic variation could potentially explain BSV, but not WSV. As to the latter, differences of bone characteristics and the bone resorption process could offer an explanation for its existence. The study has also demonstrated the importance of duplicate baseline measurements. Finally, we provide here a rationale for worst case scenarios with partly effective countermeasures in long-term space missions.

Effect of Eight-Month Exercise Intervention on Bone Outcomes of Young Opioid-Dependent Women

Objective: To evaluate the bone response to an 8 month aerobic gymnastics training program in young opioid-addicted women. Design: Randomized controlled trial (parallel design). Setting: Women’s Specific Drug Rehabilitation Center in China. Patients: One hundred and two young women with low bone quality and previous opioid addiction were divided into two groups: (a) the low bone quality intervention experimental group (n = 55; age: 30.3 ± 6.1) and (b) the low bone quality observed control group (observation group; n = 47; age: 29.0 ± 5.3). Interventions: The intervention group took aerobic gymnastics regularly for 80 min/d and 5 d/wk for 8 months and completed follow-up testing. Main Outcome Measures: Substance use history and other life habits affecting bone quality were assessed by questionnaire-based interviews. Bone quality (stiffness-index, T-score, Z-score) was examined with quantitative ultrasound. Anthropometric characteristics (body weight, fat-free mass, fat mass) were obtained by bioelectrical impedance analysis. Results: After the 8 month intervention, the stiffness index of bone quality increased significantly (before: 82 ± 6, after: 108 ± 14, p < 0.05) in the experimental group. However, the bone quality did not change significantly in the controls (before: 79 ± 10, after: 77 ± 13, p > 0.05). The bone change in the difference group was significant (experimental group: 31.7% vs observation group: -0.03%). Fat mass decreased in the experimental group (experimental group: before: 19.6 ± 3.7 kg, after: 18.8 ± 4.0 kg, p < 0.05). Meanwhile, the change in fat-free mass was the determination of the change in bone quality in the experimental group. Conclusions: Our results suggested that aerobic gymnastics intervention can be an effective strategy for the prevention and treatment of drug-induced osteoporosis in detoxification addicts.

Nutrition for Older Athletes: Focus on Sex-Differences

Regular physical exercise and a healthy diet are major determinants of a healthy lifespan. Although aging is associated with declining endurance performance and muscle function, these components can favorably be modified by regular physical activity and especially by exercise training at all ages in both sexes. In addition, age-related changes in body composition and metabolism, which affect even highly trained masters athletes, can in part be compensated for by higher exercise metabolic efficiency in active individuals. Accordingly, masters athletes are often considered as a role model for healthy aging and their physical capacities are an impressive example of what is possible in aging individuals. In the present review, we first discuss physiological changes, performance and trainability of older athletes with a focus on sex differences. Second, we describe the most important hormonal alterations occurring during aging pertaining regulation of appetite, glucose homeostasis and energy expenditure and the modulatory role of exercise training. The third part highlights nutritional aspects that may support health and physical performance for older athletes. Key nutrition-related concerns include the need for adequate energy and protein intake for preventing low bone and muscle mass and a higher demand for specific nutrients (e.g., vitamin D and probiotics) that may reduce the infection burden in masters athletes. Fourth, we present important research findings on the association between exercise, nutrition and the microbiota, which represents a rapidly developing field in sports nutrition.

Association of Dietary Total Antioxidant Capacity with Bone Mass and Osteoporosis Risk in Korean Women: Analysis of the Korea National Health and Nutrition Examination Survey 2008-2011

Antioxidant intake has been suggested to be associated with a reduced osteoporosis risk, but the effect of dietary total antioxidant capacity (TAC) on bone health and the risk of osteoporosis remains unclear. We aimed to assess the hypothesis that dietary TAC is positively associated with bone mass and negatively related to the risk of osteoporosis in Korean women. This cross-sectional study was performed using data from the Korea National Health and Nutrition Examination Survey. Dietary TAC was estimated using task automation and an algorithm with 24-h recall data. In total, 8230 pre- and postmenopausal women were divided into four groups according to quartiles of dietary TAC. Dietary TAC was negatively associated with the risk of osteoporosis (odds ratio, 0.73; 95% confidence interval, 0.54-0.99; p-value = 0.045) in postmenopausal women, but not in premenopausal women. Dietary TAC was positively associated with bone mineral content (BMC) and bone mineral density of the femoral neck and lumbar spine in postmenopausal women and BMC of the total femur and lumbar spine in premenopausal women. Our study suggests that dietary TAC is inversely associated with the risk of osteoporosis in postmenopausal women and positively associated with bone mass in both pre- and postmenopausal women.

Computational models of cardiac hypertrophy

Cardiac hypertrophy, defined as an increase in mass of the heart, is a complex process driven by simultaneous changes in hemodynamics, mechanical stimuli, and hormonal inputs. It occurs not only during pre- and post-natal development but also in adults in response to exercise, pregnancy, and a range of cardiovascular diseases. One of the most exciting recent developments in the field of cardiac biomechanics is the advent of computational models that are able to accurately predict patterns of heart growth in many of these settings, particularly in cases where changes in mechanical loading of the heart play an import role. These emerging models may soon be capable of making patient-specific growth predictions that can be used to guide clinical interventions. Here, we review the history and current state of cardiac growth models and highlight three main limitations of current approaches with regard to future clinical application: their inability to predict the regression of heart growth after removal of a mechanical overload, inability to account for evolving hemodynamics, and inability to incorporate known growth effects of drugs and hormones on heart growth. Next, we outline growth mechanics approaches used in other fields of biomechanics and highlight some potential lessons for cardiac growth modeling. Finally, we propose a multiscale modeling approach for future studies that blends tissue-level growth models with cell-level signaling models to incorporate the effects of hormones in the context of pregnancy-induced heart growth.

Masticatory muscle function affects the pathological conditions of dentofacial deformities

The causes of dentofacial deformities include various known syndromes, genetics, environmental and neuromuscular factors, trauma, and tumors. Above all, the functional effects of muscles are important, and deformation of the mandible is often associated with a mechanical imbalance of the masticatory muscles. With the vertical position of the face, weakness of the sling of the masseter muscle and medial pterygoid muscle causes dilatation of the mandibular angle. In patients with a deep bite, excessive function of the masticatory muscles is reported. Myosin heavy chain　(MyHC) properties also affect jawbone morphology. In short-face patients, the proportion of type II fibers, which are fast muscles, is high. The proportions of muscle fiber types are genetically determined but can be altered by postnatal environmental factors. Orthognathic surgery may results in the transition of MyHC to type II (fast) fibers, but excessive stretching enhances the release of inflammatory mediators and causes a shift toward a greater proportion of slow muscle fibers. This feature can be related to postoperative relapse. Bones and muscles are in close crosstalk, and it may be possible to use biochemical approaches as well as biomechanical considerations for the treatment of jaw deformities.

Lower Central Fat Increase Risk of One-Year Muscle Mass Loss in Menopausal Women

Background

Hormonal changes had been found in menopausal women. Muscle and bone mass decline after menopause and with aging, increasing the risk for sarcopenia and osteoporosis in later life. Only a few studies suggest that menopausal hormonal changes have an effect on the decline in muscle mass.

Objectives

This study aimed at evaluating the risk of muscle mass loss in menopausal women.

Materials and Methods

Menopausal women from routine physical health examination were eligible for this study. Muscle mass was determined using dual-energy X-ray absorptiometry at baseline and 1 year later. All of the patients underwent the assessments for liver and kidney function, diabetes, and hypertension, and associated comorbidities were recorded.

Results

A total of 172 patients were enrolled. 70 patients had muscle loss at 1 year, and the other 102 did not had loss. The mean age was 70.26 ± 9.93 years at the muscle loss group, while 69.25 ± 10.50 at the nonprogress group (p = 0.531). The mean body mass index was 22.96 ± 1.91 kg/m² at the muscle loss group, while 23.33 ± 3.71 kg/m² at the nonprogress group (p = 0.433). The baseline trunk limb fat mass ratio was 1.01 ± 0.20 in the muscle loss group and 1.12 ± 0.26 in the no muscle loss (p = 0.004). Using muscle mass loss as the outcome, logistical regression analysis showed that a baseline trunk limb mass ratio could predict muscle loss, and a higher baseline trunk limb mass ratio was associated with less muscle loss, while a lower trunk limb mass ratio was associated with increased muscle mass loss (p = 0.01).

Conclusion

This is the first study to investigate the risk of muscle mass loss in menopausal women. Menopausal women with higher central fat had less muscle mass loss, while lower central fat was a risk factor for muscle mass loss. Chronic kidney disease was also a risk factor for muscle mass loss in menopausal women in this study.

Muscle and bone mass in middle-aged women: role of menopausal status and physical activity

BACKGROUND

Women experience drastic hormonal changes during midlife due to the menopausal transition. Menopausal hormonal changes are known to lead to bone loss and potentially also to loss of lean mass. The loss of muscle and bone tissue coincide due to the functional relationship and interaction between these tissues. If and how physical activity counteracts deterioration in muscle and bone during the menopausal transition remains partly unresolved. This study investigated differences between premenopausal, early perimenopausal, late perimenopausal, and postmenopausal women in appendicular lean mass (ALM), appendicular lean mass index (ALMI), femoral neck bone mineral density (BMD) and T score. Furthermore, we investigated the simultaneous associations of ALM and BMD with physical activity in the above-mentioned menopausal groups.

METHODS

Data from the Estrogen Regulation of Muscle Apoptosis study were utilized. In total, 1393 women aged 47-55 years were assigned to premenopausal, early perimenopausal, late perimenopausal, and postmenopausal groups based on follicle-stimulating hormone concentration and bleeding diaries. Of them, 897 were scanned for ALM and femoral neck BMD by dual-energy X-ray absorptiometry and ALMI (ALM/height² ) and neck T scores calculated. Current level of leisure-time physical activity was estimated by a validated self-report questionnaire and categorized as sedentary, low, medium, and high.

RESULTS

Appendicular lean mass, appendicular lean mass index, femoral neck bone mineral density, and and T score showed a significant linear declining trend across all four menopausal groups. Compared with the postmenopausal women, the premenopausal women showed greater ALM (18.2, SD 2.2 vs. 17.8, SD 2.1, P < 0.001), ALMI (6.73, SD 0.64 vs. 6.52, SD 0.62, P < 0.001), neck BMD (0.969, SD 0.117 vs. 0.925, SD 0.108, P < 0.001), and T score (-0.093, SD 0.977 vs -0.459, SD 0.902, P < 0.001). After adjusting for potential confounding pathways, a higher level of physical activity was associated with greater ALM among the premenopausal [β = 0.171; confidence interval (CI) 95% 0.063-0.280], late perimenopausal (β = 0.289; CI 95% 0.174-0.403), and postmenopausal (β=0.278; CI 95% 0.179-0.376) women. The positive association between femoral neck BMD and level of physical activity was significant only among the late perimenopausal women (β = 0.227; CI 95% 0.097-0.356).

CONCLUSIONS

Skeletal muscle and bone losses were associated with the menopausal transition. A higher level of physical activity during the different menopausal phases was beneficial, especially for skeletal muscle. Menopause-related hormonal changes predispose women to sarcopenia and osteoporosis and further to mobility disability and fall-related fractures in later life. New strategies are needed to promote physical activity among middle-aged women. Longitudinal studies are needed to confirm these results.

Effects of menopausal state on lumbar decompression and fusion surgery

Menopause leads to fluctuations in androgenic hormones which directly affect bone metabolism. Bone resorption, mineralization, and remodeling at fusion sites are essential in order to obtain a solid and biomechanically stable fusion mass. Bone metabolic imbalance seen in the postmenopausal state may predispose to fusion related complications. The aim of this study was to investigate fusion outcomes in lumbar spinal fusion surgery in women based on menopausal status. A retrospective analysis of all female patients who underwent posterior lumbar decompression and fusion at a single institution from 2013 to 2017 was performed. A total of 112 patients were identified and stratified into premenopausal (n = 25) and postmenopausal (n = 87) groups. Clinical and radiographic data was assessed at 1 year follow up. Postmenopausal patients had a higher rates of pseudarthrosis (11.63% vs 0%, p = 0.08), PJK (15.1% vs 4%, p = 0.14), and revision surgery (3.5% vs 0%, p = 0.35). The number of levels fused was associated with increased risk of pseudarthrosis (OR 1.4, p = 0.02); however, there was no association between age, hormonal use, prior tobacco use, or T-score. Age was associated with increased risk of developing PJK (OR = 1.11, p = 0.01); however, PJK was not associated with menopause, hormonal use, prior tobacco use, or T-score. Revision surgery was not associated with age, hormonal use, prior tobacco use, or T-score. This study suggests that postmenopausal women may be prone to have higher rates of pseudarthrosis, PJK and revision surgery, although our results were not statistically significant. Larger studies with longer follow up will help elucidate the true effects of menopause in spine surgery.

First evidence on protective effect of exogenous melatonin supplementation against disruption of the estrogenic pathway in bone metabolism of killifish (Aphanius fasciatus)

This study was carried out to investigate the effects of exposure to estrogen antagonist nafoxidine hydrochloride (NH) and/or melatonin (Mlt) on certain bone metabolism parameters in killifish Aphanius fasciatus, a species suggested to be a suitable model for studying spinal deformities such as scoliosis. Immature females of A. fasciatus receiving 10 μg/L NH and/or 100 μg/L of Mlt were used and were sacrificed 30 days after the treatment. The spinal column, brain, and liver were collected and analyzed by various histological, biochemical, chemical, and molecular investigations. NH exposure increased frequency of histological alterations and caused signs of spinal column demineralization such as significant decrease in the percentage of nonorganic components content and calcium concentration. These changes were accompanied by decreased alkaline phosphatase activity (AP), hepatic insulin growth factor-1 (IGF-1) content, and, interestingly, cerebral Mlt concentration. Concomitant treatment with Mlt and NH enhanced expression of the gene encoding the Mlt receptor "mtnr1aa"and significantly restored the normal skeletal histology and the normal metabolism bone parameters. Our data suggest that disturbance of estrogen pathway in A. fasciatus induces cerebral Mlt depletion and, then, causes skeletal tissue alterations and bone demineralization and that exogenous Mlt supplementation has a protective effect. Thus, estrogen receptor antagonists and Mlt become important compounds to consider for the accurate prediction and assessment of bone physiology and spinal deformities in fish.

Greater maintenance of bone mineral content in male than female athletes and in sprinting and jumping than endurance athletes: a longitudinal study of bone strength in elite masters athletes

We investigated longitudinal changes in tibia bone strength in master power (jumping and sprinting) and endurance (distance) athletes of both sexes. Bone mass but not cross-sectional moment of inertia was better maintained in power than endurance athletes over time, particularly in men and independent of changes in performance.

OBJECTIVE

Assessment of effects of sex and athletic discipline (lower limb power events, e.g. sprint running and jumping versus endurance running events) on longitudinal changes in bone strength in masters athletes.

METHODS

We examined tibia and fibula bone properties at distal (4% distal-proximal tibia length) and proximal (66% length) sites using peripheral quantitative computed tomography (pQCT) in seventy-one track and field masters athletes (30 male, 41 female, age at baseline 57.0 ± 12.2 years) in a longitudinal cohort study that included at least two testing sessions over a mean period of 4.2 ± 3.1 years. Effects of time, as well as time × sex and time × discipline interactions on bone parameters and calf muscle cross-sectional area (CSA), were examined.

RESULTS

Effects of time were sex and discipline-dependent, even following adjustment for enrolment age, sex and changes in muscle CSA and athletic performance. Male sex and participation in power events was associated with better maintenance of tibia bone mineral content (BMC, an indicator of bone compressive strength) at 4% and 66% sites. In contrast, there was no strong evidence of sex or discipline effects on cross-sectional moment of inertia (CSMI, an indicator of bone bending and torsional strength-P > 0.3 for interactions). Similar sex and discipline-specific changes were also observed in the fibula.

CONCLUSIONS

Results suggest that male athletes and those participating in lower limb power-based rather than endurance-based disciplines have better maintenance of bone compressive but not bending and torsional strength.

Aging and Physiological Lessons from Master Athletes

Sedentary aging is often characterized by physical dysfunction and chronic degenerative diseases. In contrast, masters athletes demonstrate markedly greater physiological function and more favorable levels of risk factors for cardiovascular disease, osteoporosis, frailty, and cognitive dysfunction than their sedentary counterparts. In many cases, age-related deteriorations of physiological functions as well as elevations in risk factors that are typically observed in sedentary adults are substantially attenuated or even absent in masters athletes. Older masters athletes possess greater functional capacity at any given age than their sedentary peers. Impressive profiles of older athletes provide insight into what is possible in human aging and place aging back into the domain of "physiology" rather than under the jurisdiction of "clinical medicine." In addition, these exceptional aging athletes can serve as a role model for the promotion of physical activity at all ages. The study of masters athletes has provided useful insight into the positive example of successful aging. To further establish and propagate masters athletics as a role model for our aging society, future research and action are needed. © 2020 American Physiological Society. Compr Physiol 10:261-296, 2020.

Interaction of body fat percentage and height with appendicular functional muscle-bone unit

The interaction of body fat percentage and height with appendicular BMC for LBM was analyzed. Only body fat had significant negative correlation with the appendicular BMC for LBM.

PURPOSE/INTRODUCTION

For the clinical evaluation of the functional muscle-bone unit, it was proposed to evaluate the adaptation of the bone to the acting forces. A frequently used parameter for this is the total body less head bone mineral content (TBLH-BMC) determined by dual-energy X-ray absorptiometry (DXA) in relation to the total body lean body mass (LBM). Body fat percentage seemed to correlate negatively and height positively with TBLH-BMC for LBM. It was supposed that appendicular BMC for LBM is a more accurate surrogate for the functional muscle-bone unit since appendicular LBM does not incorporate the mass of internal organs. The aim of this study was to analyze the interaction of body fat percentage and height with appendicular BMC for LBM.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 1999 and 2004, whole-body DXA scans on randomly selected Americans from 8 years of age were carried out. From all eligible DXA scans, three major US ethnic groups were evaluated (non-Hispanic Whites, non-Hispanic Blacks, and Mexican Americans) for further statistical analysis.

RESULTS

For the statistical analysis, the DXA scans of 8190 non-Hispanic White children and adults (3903 female), of 4931 non-Hispanic Black children and adults (2250 female), and 5421 of Mexican American children and adults (2424 female) were eligible. Only body fat had a significant negative correlation with the appendicular BMC for LBM.

CONCLUSIONS

Only body fat had significant negative correlation with appendicular BMC for LBM, and thus, should be addressed when evaluating functional muscle-bone unit.

Quantitative analysis of modified functional muscle-bone unit and back muscle density in patients with lumbar vertebral fracture in Chinese elderly men: a case-control study

OBJECTIVES

Bone mineral density (BMD) is associated with muscle mass and quality, but little research has been done on functional muscle-bone unit and back muscle density in patients with lumbar vertebral fracture. This study used the "modified functional muscle-bone unit" concept and measured back muscle density to investigate muscle-bone interaction difference between the fracture and control group.

METHODS

This was a case-control study. A total of 52 elderly male patients (mean age 75 years) with lumbar vertebral fracture (cases) and 52 control healthy subjects were enrolled. Cross-sectional area (CSA) and density of paravertebral muscle were measured in quantitative computed tomography (QCT) images to represent the muscle mass, while the bone mineral density measured by QCT was used to represent the bone mass. The modified functional muscle-bone unit was calculated as the value of volumetric BMD divided by muscle area.

RESULTS

People with vertebral fractures reported significantly lower values in the cross-sectional area and density of paravertebral muscle compared to control group. In the multivariate analysis, BMD (odds ratio, OR = 0.929; 95% confidence intervals, CIs 0.888-0.971), erector muscle density (OR = 0.698; 95% CI 0.547-0.892), and summated muscle CSA (OR = 0.963; 95% CI 0.93-0.991) were independent protective factors for the presence of a fracture. BMD resulted significantly and moderately associated with cross-sectional area and density of paravertebral muscle (r = 0.329-0.396).

CONCLUSIONS

There were significant differences between the modified functional muscle-bone unit and back muscle density between the fracture group and control group in elderly men. Lower BMD, loss of muscle mass and density are associated with increased presence of the lumbar vertebral fracture.

Do bone geometric properties of the proximal femoral diaphysis reflect loading history, muscle properties, or body dimensions?

OBJECTIVES

The aim of this study was to investigate activity-induced effects from bone geometric properties of the proximal femur in athletic vs nonathletic healthy females by statistically controlling for variation in body size, lower limb isometric, and dynamic muscle strength, and cross-sectional area of Musculus gluteus maximus.

METHODS

The material consists of hip and proximal thigh magnetic resonance images of Finnish female athletes (N = 91) engaged in either high jump, triple jump, soccer, squash, powerlifting, endurance running or swimming, and a group of physically active nonathletic women (N = 20). Cross-sectional bone geometric properties were calculated for the lesser trochanter, sub-trochanter, and mid-shaft of the femur regions. Bone geometric properties were analyzed using a general linear model that included body size, muscle size, and muscle strength as covariates.

RESULTS

Body size and isometric muscle strength were positively associated with bone geometric properties at all three cross-sectional levels of the femur, while muscle size was positively associated with bone properties only at the femur mid-shaft. When athletes were compared to nonathletic females, triple jump, soccer, and squash resulted in greater values in all studied cross-sections; high jump and endurance running resulted in greater values at the femoral mid-shaft cross-section; and swimming resulted in lower values at sub-trochanter and femur mid-shaft cross-sections.

CONCLUSIONS

Activity effects from ground impact loading were associated with higher bone geometric values, especially at the femur mid-shaft, but also at lesser and sub-trochanter cross-sections. Bone geometric properties along the femur can be used to assess the mechanical stimuli experienced, where ground impact loading seems to be more important than muscle loading.

The Importance of Impact Loading and the Stretch Shortening Cycle for Spaceflight Countermeasures

Pronounced muscle and bone losses indicate that the musculoskeletal system suffers substantially from prolonged microgravity. A likely reason for these detrimental adaptations in the lower extremity is the lack of impact loading and the difficulty to apply large loading forces on the human body in microgravity. The human body is well adapted to ambulating in Earth’s gravitational field. A key principle herein is the periodic conversion of kinetic to elastic energy and vice versa. Predominantly tendons and to a lesser extent muscles, bones and other tissues contribute to this storage and release of energy, which is most efficient when organized in the stretch-shortening cycle (SSC). During SSC, muscles, especially those encompassing the ankle, knee, and hip joints, are activated in a specific manner, thereby enabling the production of high muscle forces and elastic energy storage. In consequence, the high forces acting throughout the body deform the viscoelastic biological structures sensed by mechanoreceptors and feedback in order to regulate the resilience of these structures and keep strains and strain rates in an uncritical range. Recent results from our lab indicate, notably, that SSC can engender a magnitude of tissue strains that cannot be achieved by other types of exercise. The present review provides an overview of the physiology and mechanics of the natural SSC as well as the possibility to mimic it by the application of whole-body vibration. We then report the evidence from bed rest studies on effectiveness and efficiency of plyometric and resistive vibration exercise as a countermeasure. Finally, implications and applications of both training modalities for human spaceflight operations and terrestrial spin-offs are discussed.

Anatomic grooved stem mitigates strain shielding compared to established total hip arthroplasty stem designs in finite-element models

Aseptic loosening remains a major problem for uncemented femoral components in primary total hip arthroplasty (THA). Ideally, bone adaptation after THA manifests minimally and local bone density reduction is widely avoided. Different design features may help to approximate initial, post-THA bone strain to levels pre-THA. Strain-shielding effects of different SP-CL stem design features are systematically analyzed and compared to CLS Spotorno and CORAIL using finite element models and physiological musculoskeletal loading conditions. All designs show substantial proximal strain-shielding: 50% reduced medial surface strain, 40–50% reduction at lateral surface, >120 µm/m root mean square error (RMSE) compared to intact bone in Gruen zone 1 and >60 µm/m RMSE in Gruen zones 2, 6, and 7. Geometrical changes (ribs, grooves, cross sections, stem length, anatomic curvature) have a considerable effect on strain-shielding; up to 20%. Combinations of reduced stem stiffness with larger proximal contact area (anatomically curved, grooves) lead to less strain-shielding compared to clinically established implant designs. We found that only the combination of a structurally flexible stem with anatomical curvature and grooves improves strain-shielding compared to other designs. The clinical implications in vivo of this initial strain-shielding difference are currently under evaluation in an ongoing clinical analysis.

Discrimination of vertebral fragility fracture with lumbar spine bone mineral density measured by quantitative computed tomography

Background/Objective

This study is a case–control study to explore risk and protective factors, including clinical data and bone mineral density (BMD), affecting vertebral body fragility fracture in elderly men and postmenopausal women. In addition, we investigate the effectiveness of lumbar spine BMD by quantitative computed tomography (QCT) in discriminating vertebral fragility fracture.

Methods

In this case–control study, 52 males and 198 females with vertebral fragility fracture were compared with sex- and age-matched healthy controls to analyse the risk factors that may affect vertebral fragility fracture. The L1–L3 vertebral BMDs were measured by QCT. The difference in risk factors between fracture cases and controls were analysed using student t test and Mann–Whitney U test. The correlation between BMD, age, height and weight were analysed using univariate analysis. Multiple logistic regression analysis was used to study statistically significant indexes. The receiver operating characteristic curve was used to calculate the cut-off values for positive and negative predictive values of BMD for vertebral fracture discrimination.

Results

In males, body weight and BMD were significantly different between the fracture group and the control group, whereas BMD was only weakly correlated with age (r = −0.234). In females, only BMD was significantly different between the fracture and control groups. BMD was weakly correlated with height (r = 0.133) and weight (r = 0.120) and was moderately correlated with age (r = −0.387). There was no correlation between BMD and the remaining variables in this study. In both men and women, the BMD (p = 0.000) was the independent protective factor against vertebral fracture. The cut-off values of vertebral BMD for fractures were 64.16 mg/cm³ for males and 55.58 mg/cm³ for females. QCT-measured BMD has a high positive predictive value and negative predictive value for discriminating vertebral fragility fracture across a range of BMD values.

Conclusion

This study suggests that BMD is closely related to vertebral fragility fracture and that QCT is an effective technique to accurately discriminate vertebral fragility fracture.

The translational potential of this article

The spine BMD measured by QCT is closely related to fracture, which may allow clinicians to more accurately discriminate which individuals are likely to experience vertebral fragility fracture.

Effects of reproduction on sexual dimorphisms in rat bone mechanics

Osteoporosis most commonly affects postmenopausal women. Although men are also affected, women over 65 are 6 times more likely to develop osteoporosis than men of the same age. This is largely due to accelerated bone remodeling after menopause; however, the peak bone mass attained during young adulthood also plays an important role in osteoporosis risk. Multiple studies have demonstrated sexual dimorphisms in peak bone mass, and additionally, the female skeleton is significantly altered during pregnancy/lactation. Although clinical studies suggest that a reproductive history does not increase the risk of developing postmenopausal osteoporosis, reproduction has been shown to induce long-lasting alterations in maternal bone structure and mechanics, and the effects of pregnancy and lactation on maternal peak bone quality are not well understood. This study compared the structural and mechanical properties of male, virgin female, and post-reproductive female rat bone at multiple skeletal sites and at three different ages. We found that virgin females had a larger quantity of trabecular bone with greater trabecular number and more plate-like morphology, and, relative to their body weight, had a greater cortical bone size and greater bone strength than males. Post-reproductive females had altered trabecular microarchitecture relative to virgins, which was highly similar to that of male rats, and showed similar cortical bone size and bone mechanics to virgin females. This suggests that, to compensate for future reproductive bone losses, females may start off with more trabecular bone than is mechanically necessary, which may explain the paradox that reproduction induces long-lasting changes in maternal bone without increasing postmenopausal fracture risk.

Indian girls have higher bone mineral content per unit of lean body than boys through puberty

Our aim is to describe changes in the muscle-bone unit assessed as a ratio of bone mineral content (BMC) to lean body mass (LBM) through puberty at total body and various skeletal sites in Indian boys and girls. A cross-sectional study was conducted (888 children, 480 boys, aged 5-17 years) in Pune, India. Pubertal staging was assessed. BMC, LBM and fat percentage at the arms, legs, android, gynoid and total body (less the head) were assessed by dual energy X-ray absorptiometry. The amount of BMC per unit LBM (BMC/LBM) was computed. Changes in mean BMC/LBM at 5 Tanner (pubertal) stages after adjustment for age and fat percentage were calculated. In boys, adjusted BMC/LBM was significantly higher with successive Tanner stages [legs (TS-II vs TS-I), android (TS-III vs TS-II, TS-IV vs TS-III) and gynoid region (TS-III vs TS-II and TS-II vs TS-I) (p < 0.05)]. In girls, adjusted BMC/LBM was significantly higher with successive Tanner stages at total body, legs and gynoid (TS-III vs TS-II; TS-II vs TS-I; TS-V vs TS-IV), arms (TS-I to TS-V) and android regions (TS-V vs TS-IV) (p < 0.05). Boys had significantly higher adjusted BMC/LBM than girls at earlier Tanner stages (TS-I to TS-III), whereas girls had significantly higher adjusted BMC/LBM than boys at later Tanner stages (TS-IV, TS-V) (p < 0.05). Indian boys and girls showed higher total and regional body, and age- and fat percentage-adjusted BMC/LBM with successive pubertal stages. Girls had higher BMC/LBM than boys which may possibly act as a reservoir for later demands of pregnancy and lactation.

Are there effects of age, gender, height, and body fat on the functional muscle-bone unit in children and adults?

The aim was to describe the effect of age, gender, height, different stages of human life, and body fat on the functional muscle-bone unit. All these factors had a significant effect on the functional muscle-bone unit and should be addressed when assessing functional muscle-bone unit in children and adults.

INTRODUCTION

For the clinical evaluation of the functional muscle-bone unit, it was proposed to evaluate the adaptation of the bone to the acting forces. A frequently used parameter for this is the total body less head bone mineral content (TBLH-BMC) determined by dual-energy X-ray absorptiometry (DXA) in relation to the lean body mass (LBM by DXA). LBM correlates highly with muscle mass. Therefore, LBM is a surrogate parameter for the muscular forces acting in everyday life. The aim of the study was to describe the effect of age and gender on the TBLH-BMC for LBM and to evaluate the impact of other factors, such as height, different stages of human life, and of body fat.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 1999-2006 whole-body DXA scans on randomly selected Americans from 8 years of age were carried out. From all eligible DXA scans (1999-2004), three major US ethnic groups were evaluated (non-Hispanic Whites, non-Hispanic Blacks, and Mexican Americans) for further statistical analysis.

RESULTS

For the statistical analysis, the DXA scans of 8190 non-Hispanic White children and adults (3903 female), of 4931 non-Hispanic Black children and adults (2250 female) and 5421 of Mexican-American children and adults (2424 female) were eligible. Age, gender, body height, and especially body fat had a significant effect on the functional muscle-bone unit.

CONCLUSIONS

When assessing TBLH-BMC for LBM in children and adults, the effects of age, gender, body fat, and body height should be addressed. These effects were analyzed for the first time in such a large cohort.

Impact of Age, Gender, and Body Composition on Bone Quality in an Adult Population From the Middle Areas of China

Identifying modifiable factors that influence bone status during adulthood to maximize bone quality is a potential primary strategy in the prevention of osteoporosis in later life. We investigated the impact of body height, body weight, body mass index, and body composition on calcaneal bone characteristics as measured with quantitative ultrasound in 441 Chinese adults (238 women) aged 20-55 yr from the middle areas of China. Body composition, including fat-free mass (FFM), muscle mass, and fat mass were obtained by bioelectrical impedance analysis. Bivariate correlation analysis demonstrated a significant negative correlation between age and broadband ultrasound attenuation (BUA), speed of sound (SOS), and stiffness index (SI) both in men (r = -0.177, p < 0.05; r = -0.499, p < 0.001; r = -0.530, p < 0.001, respectively) and women (r = -0.344, p < 0.001; r = -0.336, p < 0.001; r = -0.369, p < 0.001, respectively). Body height, body weight, FFM, and muscle mass had positive correlations with BUA, SOS, and SI in both genders, with FFM having the strongest correlation with BUA, SOS, and SI in men (r = 0.351, p < 0.001; r = 0.391, p < 0.001; r = 0.406, p < 0.001, respectively) and women (r = 0.331, p < 0.001; r = 0.288, p < 0.001; r = 0.324, p < 0.001, respectively). Fat mass had a positive correlation with BUA (r = 0.331, p < 0.001), SOS (r = 0.288, p < 0.001), and SI (r = 0.324, p < 0.001) in women, which was not found in men. Multivariate regression analysis revealed that, in both genders, FFM was a positive predictor for all 3 quantitative ultrasound variables.

Causes of low peak bone mass in women

Peak bone mass is the maximum bone mass that accrues during growth and development. Consolidation of peak bone mass normally occurs during early adulthood. Low peak bone mass results from failure to achieve peak bone mass genetic potential, primarily due to bone loss caused by a variety of conditions or processes occurring at younger ages than usual. Recognized causes of low peak bone mass include genetic causes, endocrine disorders, nutritional disorders, chronic diseases of childhood or adolescence, medications, and idiopathic factors.

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.

Low Habitual Dietary Calcium and Linear Growth from Adolescence to Young Adulthood: results from the China Health and Nutrition Survey

Evidences from clinical trials and meta-analyses of calcium supplementation in linear growth have given conflicting results, and few longitudinal studies have investigated the long-term associations between dietary calcium and linear growth, especially in the population with low-calcium plant-based diets. We investigated the prospective associations of low habitual dietary calcium with adult height and height-for-age z-score (HAZ) from adolescence to adulthood among 2019 adolescents from the China Health and Nutrition Survey (CHNS). The average dietary calcium intakes were 426(standard deviation: 158) mg/d in boys and 355(134) mg/d in girls during adolescence. During a median follow-up of 7.0 (interquartile range: 5.9–9.0) years, boys reached an average of 169.0(6.7) cm and girls reached 158.4(5.8) cm in adulthood. After adjusting for other potential confounders, non-linear regression found that boys with dietary calcium intakes below 327 mg/d had shorter adult stature, and those taking over 566 mg/d had faster height growth whether adjusting for physical exercises level or not. No significant associations were found in girls. Our study suggests that in boys with plant-based diets, higher dietary calcium intake during adolescence is associated with faster height growth, but not with adult height; calcium intake below 300 mg/d may result in shorter adult stature.

The functional muscle-bone unit in children with cerebral palsy

Our results suggest that the prevalence of bone health deficits in children with CP was overestimated, when using only age- and height-adjusted bone mineral content (BMC) and areal bone mineral density (aBMD). When applying the functional muscle-bone unit diagnostic algorithm (FMBU-A), the prevalence of positive results decreased significantly. We recommend applying the FMBU-A when assessing bone health in children with CP.

INTRODUCTION

The prevalence of bone health deficits in children with cerebral palsy (CP) might be overestimated because age- and height-adjusted reference percentiles for bone mineral content (BMC) and areal bone mineral density (aBMD) assessed by dual-energy X-ray absorptiometry (DXA) do not consider reduced muscle activity. The aim of this study was to compare the prevalence of positive DXA-based indicators for bone health deficits in children with CP to the prevalence of positive findings after applying a functional muscle-bone unit diagnostic algorithm (FMBU-A) considering reduced muscle activity.

METHODS

The present study was a monocentric retrospective analysis of 297 whole body DXA scans of children with CP. The prevalence of positive results of age- and height-adjusted BMC and aBMD defined as BMC and aBMD below the P3 percentile and of the FMBU-A was calculated.

RESULTS

In children with CP, the prevalence of positive results of age-adjusted BMC were 33.3% and of aBMD 50.8%. Height-adjusted results for BMC and aBMD were positive in 16.8 and 36.0% of cases. The prevalence of positive results applying the FMBU-A regarding BMC and aBMD were significantly (p < 0.001) lower than using age- and height-adjusted BMC and aBMD (8.8 and 14.8%).

CONCLUSIONS

Our results suggest that the prevalence of bone health deficits in children with CP was overestimated, when using age- and height-adjusted BMC and aBMD. When applying the FMBU-A, the prevalence decreased significantly. We recommend applying the FMBU-A when assessing bone health in children with CP.

A comparison of bone quality and its determinants in young opioid-dependent women with healthy control group

BACKGROUND

Little is known about bone quality and its determinants in patients with opioid addiction. The goal of this study was to compare bone quality and its determinants in young opioid addicted women with a local group of young healthy women.

METHOD

Using cross-sectional design, 104 women (mean age 29.9 yrs, range: 20-40 yrs, SD=7.8) with previous opioid addiction and current methadone substitution (3-30mg, daily) for 1-16 weeks were compared to 117 healthy women (mean age 31.0 yrs, range: 20-40 yrs, SD=5.9). Bone quality was examined with quantitative ultrasound. Anthropometric characteristics (body weight, fat free mass (FFM), fat mass) were obtained by bioelectrical impedance analysis. Substance use and other risk factors for low bone quality were assessed by questionnaire-based interviews.

RESULTS

More than one-quarter (34%) of patients had osteopenia (n=31) or osteoporosis (n=4), compared to 16% of the healthy control group having osteopenia (n=18). Bivariate correlation analysis demonstrated that age, body weight, and FFM correlated with bone quality (p<0.05) in healthy women, which were not found in patients. Multivariate analyses showed that in healthy controls, the determinants of bone quality were age, body height, physical activity, and BMI, but in patients, the determinant of bone quality was duration of drug intake.

CONCLUSIONS

Long-term opioid dependence in young women may lead to low bone quality. Efforts to increase awareness of low bone quality in young opioid addicted women should be considered so that effective treatment may be employed to lower future fracture risk.

The effect of body composition and serum inflammatory markers on the functional muscle-bone unit in premenopausal women

BACKGROUND/OBJECTIVES

A number of recent studies dealing with the relationship between the effects of high body mass (BM) and fat mass (FM) on bone mass and strength exhibit a range of contrasting variations in their findings. These diverse findings have led to an ongoing controversy as to whether high BM and FM positively or negatively affect bone mass and strength. Excessive FM and the associated low-grade inflammation might overturn the higher mechanical stimulus arising from a higher BM. Therefore, we aimed at quantifying the functional muscle-bone unit in premenopausal women with markedly diverging body composition.

SUBJECTS/METHODS

Sixty-four young women with BMs ranging from 50 to 113 kg and body fat percentages between 20.7% and 51.8% underwent jumping mechanography and peripheral quantitative computed tomography measurements. Maximum voluntary ground reaction force during multiple one-legged hopping (F_m1LH), as well as bone characteristics at 4, 14 and 38% of tibia length, were determined. Body composition was assessed by dual-energy X-ray absorptiometry, and serum inflammatory markers were analyzed from blood samples.

RESULTS

F_m1LH predicted volumetric bone mineral content at the 14% site by 48.7%. Women with high body fat percentage had significantly higher F_m1LH, significantly lower relative bone mass, relative bone strength and relative bone area, as well as higher serum inflammatory markers in comparison to women with lower body fat percentage.

CONCLUSIONS

In conclusion, high body fat percentage was associated with lower relative bone mass and strength despite normal habitual muscle force in premenopausal women, indicating that high body fat percentage compromised the functional muscle-bone unit in these individuals.

The Biphasic Effect of Vitamin D on the Musculoskeletal and Cardiovascular System

This narrative review summarizes beneficial and harmful vitamin D effects on the musculoskeletal and cardiovascular system. Special attention is paid to the dose-response relationship of vitamin D with clinical outcomes. In infants and adults, the risk of musculoskeletal diseases is highest at circulating 25-hydroxyvitamin D (25OHD) concentrations below 25 nmol/L and is low if 40-60 nmol/L are achieved. However, evidence is also accumulating that in elderly people the risk of falls and fractures increases again at circulating 25OHD levels > 100 nmol/L. Cohort studies report a progressive increase in cardiovascular disease (CVD) events at 25OHD levels < 50 nmol/L. Nevertheless, meta-analyses of randomized controlled trials suggest only small beneficial effects of vitamin D supplements on surrogate parameters of CVD risk and no reduction in CVD events. Evidence is accumulating for adverse vitamin D effects on CVD outcomes at 25OHD levels > 100 nmol/L, but the threshold may be influenced by the level of physical activity. In conclusion, dose-response relationships indicate deleterious effects on the musculoskeletal system and probably on the cardiovascular system at circulating 25OHD levels < 40-60 nmol/L and >100 nmol/L. Future studies should focus on populations with 25OHD levels < 40 nmol/L and should avoid vitamin D doses achieving 25OHD levels > 100 nmol/L.

Bone Structure and Geometric Properties at the Radius and Tibia in Adolescent Endurance-Trained Cyclists

OBJECTIVE

To describe cortical and trabecular volumetric bone mineral density (vBMD), bone mineral content (BMC), cross-sectional area (CSA), and bone strength indexes (BSIs) in adolescent endurance-trained cyclists (CYC) and compare them with controls (CON).

DESIGN

Descriptive cohort study.

PARTICIPANTS

Twenty-five male adolescent CYC and 17 CON.

ASSESSMENT OF RISK FACTORS

Peripheral quantitative computed tomography was used to evaluate proximal and distal sites of the radius and tibia.

MAIN OUTCOME MEASURES

Total, trabecular, and cortical BMC, vBMD, and CSA were measured. Also, cortical thickness, endosteal and periosteal circumferences, and different BSIs were calculated. Unadjusted analysis of variance and body weight-adjusted analysis of covariance tests were applied between cyclist and control groups.

RESULTS

Cyclists were almost 12% lighter than CON (P < 0.05). Unadjusted data showed lower distal total vBMD and proximal cortical BMC and vBMD in cyclists compared with CON at the radius (P < 0.05) and lower distal total and trabecular BMC, vBMD and bone area, proximal total and cortical BMC and vBMD, and cortical bone area at the tibia (P < 0.05). Body weight-adjusted data showed the same differences for distal total vBMD at the radius and total and trabecular BMC and vBMD at the tibia, diaphyseal radius cortical vBMD and tibia total vBMD, cortical BMC and area, and also for tibia cortical thickness and BSI. The rest of differences were no longer detectable and bone area at the distal radius become significantly higher in cyclist compared with CON (P < 0.05).

CONCLUSIONS

Adolescent CYC in this study showed lower values of BMC and vBMD at determined sites of the radius and tibia than CON, some of these differences were explained in part by their lower body weight. However, even further adjustment, some differences remained, which indicates that further longitudinal studies are needed to better understand if cycling influences these differences.

[Intensive training and menstrual disorders in young female: Impact on bone mass]

Participation in recreational physical activity is widely acknowledged to provide significant health benefits. Conversely, intense training imposes several constraints, such as intermittent or chronic metabolic and psychogenic training stressors and maintenance of very low body fat to maximize performance. Adolescent and adult athletic women are therefore at risk of overtraining and/or poor dietary intake, which may have several consequences for endocrine function particularly on hypothalamic-pituitary-gonadal axis. Female athletes, particularly those participating in sports needing leanness or low body weight, present a high prevalence of menstrual disorders with clinical manifestations ranging from delayed menarche, oligomenorrhea to primary and secondary amenorrhea. A high degree of variability according to the type of sport and the intensity of the practice is however observed. Exercise-related reproductive dysfunction may have some consequences for growth velocity and peak bone mass acquisition during adolescence and bone pathologies in adults. Recent findings highlight the endocrine role of adipose tissue and energy balance in the regulation of homeostasis and reproductive function. A better understanding of the mechanisms whereby intense training affects the endocrine systems may orient research to develop innovative strategies probably based on individualized nutritional approach to improve the medical care of these female athletes and protect their reproductive function.

Peripheral quantitative computed tomography (pQCT) for the assessment of bone strength in most of bone affecting conditions in developmental age: a review

Peripheral quantitative computed tomography provides an automatical scan analysis of trabecular and cortical bone compartments, calculating not only their bone mineral density (BMD), but also bone geometrical parameters, such as marrow and cortical Cross-Sectional Area (CSA), Cortical Thickness (CoTh), both periosteal and endosteal circumference, as well as biomechanical parameters like Cross-Sectional Moment of Inertia (CSMI), a measure of bending, polar moment of inertia, indicating bone strength in torsion, and Strength Strain Index (SSI). Also CSA of muscle and fat can be extracted. Muscles, which are thought to stimulate bones to adapt their geometry and mineral content, are determinant to preserve or increase bone strength; thus, pQCT provides an evaluation of the functional 'muscle-bone unit', defined as BMC/muscle CSA ratio. This functional approach to bone densitometry can establish if bone strength is normally adapted to the muscle force, and if muscle force is adequate for body size, providing more detailed insights to targeted strategies for the prevention and treatment of bone fragility. The present paper offers an extensive review of technical features of pQCT and its possible clinical application in the diagnostic of bone status as well as in the monitoring of the skeleton's health follow-up.

Bone Mass and Strength in School-Age Children Exhibit Sexual Dimorphism Related to Differences in Lean Mass: The Generation R Study

Bone strength, a key determinant of fracture risk, has been shown to display clear sexual dimorphism after puberty. We sought to determine whether sex differences in bone mass and hip bone geometry as an index of strength exist in school-age prepubertal children and the degree to which the differences are independent of body size and lean mass. We studied 3514 children whose whole-body and hip scans were measured using the same densitometer (GE-Lunar iDXA) at a mean age of 6.2 years. Hip dual-energy X-ray absorptiometry (DXA) scans underwent hip structural analyses (HSA) with derivation of bone strength indices. Sex differences in these parameters were assessed by regression models adjusted for age, height, ethnicity, weight, and lean mass fraction (LMF). Whole-body bone mineral density (BMD) and bone mineral content (BMC) levels were 1.3% and 4.3% higher in girls after adjustment by LMF. Independent of LMF, boys had 1.5% shorter femurs, 1.9% and 2.2% narrower shaft and femoral neck with 1.6% to 3.4% thicker cortices than girls. Consequent with this geometry configuration, girls observed 6.6% higher stresses in the medial femoral neck than boys. When considering LMF, the sexual differences on the derived bone strength indices were attenuated, suggesting that differences in muscle loads may reflect an innate disadvantage in bone strength in girls, as consequence of their lower muscular acquisition. In summary, we show that bone sexual dimorphism is already present at 6 years of age, with boys having stronger bones than girls, the relation of which is influenced by body composition and likely attributable to differential adaptation to mechanical loading. Our results support the view that early life interventions (ie, increased physical activity) targeted during the pre- and peripubertal stages may be of high importance, particularly in girls, because before puberty onset, muscle mass is strongly associated with bone density and geometry in children. © 2015 American Society for Bone and Mineral Research.

Bone Fragility in Turner Syndrome: Mechanisms and Prevention Strategies

Bone fragility is recognized as one of the major comorbidities in Turner syndrome (TS). The mechanisms underlying bone impairment in affected patients are not clearly elucidated, but estrogen deficiency and X-chromosomal abnormalities represent important factors. Moreover, although many girls with TS undergo recombinant growth hormone therapy to treat short stature, the efficacy of this treatment on bone mineral density is controversial. The present review will focus on bone fragility in subjects with TS, providing an overview on the pathogenic mechanisms and some prevention strategies.

Skeletal muscle and pediatric bone development

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent clinical findings surrounding the muscle-bone relationships in children, while considering muscle adiposity, endocrine factors, and lifestyle influences (i.e., diet and exercise) involved in pediatric musculoskeletal development.

RECENT FINDINGS

Positive relationships between cortical bone geometry and muscle mass, size and function have been reported. Prospective studies in particular have helped clarify some of the inconsistent relationships between muscle and cortical bone volumetric density. Muscle fat is associated with impaired glucose handling and muscular functionality, which may in turn have a downstream effect on cortical bone growth during adolescence. Lifestyle factors such as healthful diets and higher impact physical activities can promote optimal skeletal development by improving the muscular phenotype and endocrine profile.

SUMMARY

Muscle and bone are two intricately-related tissue types; however, factors such as sex, maturation, study design, and outcome measures studied can modify this relationship. Further research is warranted to understand the impact of muscle adiposity on cardiometabolic health, muscle function and, subsequently, pediatric musculoskeletal development and fracture risk. Following age-specific diet and physical activity recommendations should be a major focus in obtaining optimal muscle and bone development throughout maturation.

Ontogeny of the male femur: Geometric morphometric analysis applied to a contemporary Spanish population

OBJECTIVE

To describe the morphological changes of the male femur during the adolescent growth spurt and to compare the pattern obtained with that reported previously for females.

MATERIAL AND METHODS

Two hundred and forty males from a Spanish population aged between 9 and 16 years were analysed, based on telemetries. Size and shape variation of the femur was quantified by 22 2D-landmarks and analysed using geometric morphometric methods. Likewise, the variation of neck-shaft and bicondylar angles were also determined and evaluated by Student's t-test. Sexual differences were analysed by comparing results here obtained on boys with those corresponding to girls reported in a previous study.

RESULTS

In males, both size and shape varied significantly with age, with males having larger dimensions than females. In general terms, these changes are generally characterised by an increase in robustness of the femur and shape modifications in the epiphyses. During growth, the neck-shaft angle decreases and the size of the greater and lesser trochanters increase. A significant increase of distal epiphyseal dimensions was recorded, mainly in the medial condyle. The angular remodeling of both the neck and the bicondylar regions of the male femur continues until 16 and 15 years, respectively. Female and male femur each followed divergent growth trajectories. Males showed a greater variability in neck-shaft and bicondylar angles than females.

DISCUSSION

The timing, morphology and growth trajectories provided on the femur during development can be very helpful in anthropological, paleoanthropological and evolution studies.

Sex-, age-, and height-specific reference curves for the 6-min walk test in healthy children and adolescents

The 6-min walk test is a simple and accurate method to measure functional exercise capacity in children. We provide smooth reference curves for the modified 6-min walk test in 696 healthy children and adolescents aged 4-19 years, enabling calculation of sex-, age-, and height-specific Z-scores.

CONCLUSION

These reference curves will allow more accurate grading of mobility and exercise capacity in sick or disabled children and monitoring the effects of intervention or treatment.

The muscle-bone interaction in Turner syndrome

OBJECTIVES

Turner syndrome (TS) is associated with an increased fracture rate due to reduced bone strength, which is mainly determined by skeletal muscle force. This study aimed to assess the muscle force-bone strength relationship in TS and to compare it with that of healthy controls.

METHODS

This study included 39 girls with TS and 67 healthy control girls. Maximum muscle force (Fmax) was assessed through multiple one-legged hopping with jumping mechanography. Peripheral quantitative computerized tomography assessed the bone strength index at the tibial metaphysis (BSI 4) and the polar strength-strain index at the diaphysis (SSI polar 66). The effect of TS on the muscle-bone unit was tested using multiple linear regression.

RESULTS

TS had no impact on Fmax (p=0.14); however, a negative effect on bone strength (p<0.001 for BSI 4 and p<0.01 for SSI polar 66) was observed compared with healthy controls. Bone strength was lower in the TS group (by 18%, p<0.01, for BSI 4 and by 7%, p=0.027, for SSI polar 66), even after correcting for Fmax.

CONCLUSIONS

Similar muscle force induces lower bone strength in TS compared with healthy controls, which suggests altered bone-loading sensitivity in TS.

Alterations in bone mineral density and lower extremity lean mass after hip arthroscopy in a professional female Ironman triathlete: a case study

INTRODUCTION

Femoroacetabular impingement is a pathomechanical condition of the hip, which is often treated through arthroscopic techniques. The ensuing immobilization period is associated with decreases in muscle mass and bone mass. To date, minimal knowledge is present about the development of tissue mass during the considerably short rehabilitation period before returning to competition in elite endurance athletes.

CASE DESCRIPTION

Before and after surgery, a professional female Ironman triathlete underwent dual-energy X-ray absorptiometry and peripheral quantitative computed tomography measurements.

DISCUSSION AND EVALUATION

Areal bone mineral density (aBMD) of the proximal femur and lower extremity lean mass decreased in the surgically treated lower extremity during the two-month period of immobilization after the hip arthroscopy. These losses were compensated for after only six weeks of rehabilitation. A similar progression of aBMD values was observed in the lumbar spine. The adaptational pattern in volumetric BMD (vBMD) and volumetric bone mineral content (vBMC) of the tibiae were more complex, but attained pre-immobilization values for most variables also after six weeks of rehabilitation. All other variables attained pre-immobilization values no later than nine months after the surgical intervention.

CONCLUSIONS

The athlete showed a high plasticity of bone and lean tissue with an optimal short- and midterm outcome. Following a two months immobilization period after a hip arthroscopy, aBMD, vBMD and vBMC achieved pre-surgical levels after four months of rehabilitation in a female Ironman triathlete. A nine-month follow-up measurement confirmed the safety of the fast return to sport.

Muscle function in Turner syndrome: normal force but decreased power

OBJECTIVE

Although hypogonadism and SHOX gene haploinsufficiency likely cause the decreased bone mineral density and increased fracture rate associated with Turner syndrome (TS), the exact mechanism remains unclear. We tested the hypothesis that muscle dysfunction in patients with TS contributes to increased fracture risk. The secondary aim was to determine whether menarche, hormone therapy duration, positive fracture history and genotype influence muscle function parameters in patients with TS.

DESIGN

A cross-sectional study was conducted in a single university hospital referral centre between March 2012 and October 2013.

PATIENTS

Sixty patients with TS (mean age of 13·7 ± 4·5 years) were compared to the control group of 432 healthy girls.

MEASUREMENTS

A Leonardo Mechanograph(®) Ground Reaction Force Platform was used to assess muscle force (Fmax ) by the multiple one-legged hopping test and muscle power (Pmax ) by the single two-legged jump test.

RESULTS

While the Fmax was normal (mean weight-specific Z-score of 0·11 ± 0·77, P = 0·27), the Pmax was decreased in patients with TS (Z-score of -0·93 ± 1·5, P < 0·001) compared with healthy controls. The muscle function parameters were not significantly influenced by menarcheal stage, hormone therapy duration, fracture history or genotype (linear regression adjusted for age, weight and height; P > 0·05 for all).

CONCLUSION

Fmax , a principal determinant of bone strength, is normal in patients with TS. Previously described changes in bone quality and structure in TS are thus not likely related to inadequate mechanical loading but rather represent a primary bone deficit. A decreased Pmax indicates impaired muscle coordination in patients with TS.