Bone mineral density of the proximal femur is not related to dynamic joint loading during locomotion in young women

Relationship between stair ascent gait speed, bone density and gait characteristics of postmenopausal women

Stair ascent is a biomechanically challenging task for older women. Bone health may affect gait stability during stair walking. This study investigated the gait biomechanics associated with stair ascent in a group of postmenopausal women in relation to walking speed and bone health, quantified by T-score. Forty-five healthy women (mean (SD) age: 67 (14) years), with bone density ranging from healthy to osteoporotic (T-score range +1 to -3), ascended a custom-made five-step staircase with two embedded force plates, surrounded by 10 motion capture cameras, at their self-selected speed. Multivariate regression analyses investigated the explained variance in gait parameters in relation to stair ascent speed and T-score of each individual. Stair ascent speed was 0.65 (0.1) m·s-1 and explained the variance (R2 = 9 to 47%, P ≤ 0.05) in most gait parameters. T-score explained additional variance in stride width (R2 = 20%, P = 0.014), pelvic hike (R2 = 19%, P = 0.011), pelvic drop (R2 = 21%, P = 0.007) and hip adduction (R2 = 7%, P = 0.054). Increased stride width, and thereby a wider base of support, accompanied by increased frontal plane hip kinematics, could be important strategies to improve dynamic stability during stair ascent among this group of women. These findings suggest that targeted exercises of the hip abductors and adductors, including core trunk musculature, could improve dynamic stability during more challenging locomotor tasks. Balance exercises that challenge base of support could also benefit older women with low bone mineral density who may be at risk of falls.

Effect of Whole-Body Vibration Exercise on Power Profile and Bone Mineral Density in Postmenopausal Women With Osteoporosis: A Randomized Controlled Trial

OBJECTIVE

The purpose of this study was to investigate the effect of whole-body vibration (WBV) on muscle work and bone mineral density (BMD) of the lumbar vertebrae and femur in postmenopausal women.

METHODS

Forty-three postmenopausal women with low BMD were randomly assigned to WBV and control groups. Both groups received calcium and vitamin D supplementations once daily, while the WBV group additionally received WBV exercise (twice/wk) for 24 successive weeks. Qualisys gait analysis system was used to measure hip power generation by hip extensors (H1S) and flexors (H3S), hip power absorption by hip flexors (H2S), knee power absorption by quadriceps during loading response (K1S) and preswing (K3S), knee power absorption by hamstring (K4S), knee power generation by quadriceps (K2S), ankle power absorption by dorsiflexors (A1S) and plantar flexors (A2S), and ankle power generation by plantar flexors (A3S). Also, dual-energy X-ray absorptiometry was used to measure BMD of the lumbar vertebrae and femur before and after the intervention.

RESULTS

There were significant increases (P < .05) in the hip muscle work (H1S, H2S, and H3S), knee muscle work (K1S, K2S, K3S, and K4S), ankle muscle work (A1S, A2S, and A3S) during gait, and BMD of the lumbar vertebrae and femur of the WBV group. However, there were no significant changes (P > .05) in the control group. The posttreatment values of the hip, knee, and ankle muscle work and BMD of the WBV group were significantly (P < .05) higher than the posttreatment values of the control group.

CONCLUSION

Whole-body vibration training improved the leg muscle work and lumbar and femoral BMD in postmenopausal women with low BMD.

Myokines: The endocrine coupling of skeletal muscle and bone

Bone and skeletal muscle are integrated organs and their coupling has been considered mainly a mechanical one in which bone serves as attachment site to muscle while muscle applies load to bone and regulates bone metabolism. However, skeletal muscle can affect bone homeostasis also in a non-mechanical fashion, i.e., through its endocrine activity. Being recognized as an endocrine organ itself, skeletal muscle secretes a panel of cytokines and proteins named myokines, synthesized and secreted by myocytes in response to muscle contraction. Myokines exert an autocrine function in regulating muscle metabolism as well as a paracrine/endocrine regulatory function on distant organs and tissues, such as bone, adipose tissue, brain and liver. Physical activity is the primary physiological stimulus for bone anabolism (and/or catabolism) through the production and secretion of myokines, such as IL-6, irisin, IGF-1, FGF2, beside the direct effect of loading. Importantly, exercise-induced myokine can exert an anti-inflammatory action that is able to counteract not only acute inflammation due to an infection, but also a condition of chronic low-grade inflammation raised as consequence of physical inactivity, aging or metabolic disorders (i.e., obesity, type 2 diabetes mellitus). In this review article, we will discuss the effects that some of the most studied exercise-induced myokines exert on bone formation and bone resorption, as well as a brief overview of the anti-inflammatory effects of myokines during the onset pathological conditions characterized by the development a systemic low-grade inflammation, such as sarcopenia, obesity and aging.

Physical Activity and Bone Health: What Is the Role of Immune System? A Narrative Review of the Third Way

Bone tissue can be seen as a physiological hub of several stimuli of different origin (e.g., dietary, endocrine, nervous, immune, skeletal muscle traction, biomechanical load). Their integration, at the bone level, results in: (i) changes in mineral and protein composition and microarchitecture and, consequently, in shape and strength; (ii) modulation of calcium and phosphorous release into the bloodstream, (iii) expression and release of hormones and mediators able to communicate the current bone status to the rest of the body. Different stimuli are able to act on either one or, as usual, more levels. Physical activity is the key stimulus for bone metabolism acting in two ways: through the biomechanical load which resolves into a direct stimulation of the segment(s) involved and through an indirect load mediated by muscle traction onto the bone, which is the main physiological stimulus for bone formation, and the endocrine stimulation which causes homeostatic adaptation. The third way, in which physical activity is able to modify bone functions, passes through the immune system. It is known that immune function is modulated by physical activity; however, two recent insights have shed new light on this modulation. The first relies on the discovery of inflammasomes, receptors/sensors of the innate immunity that regulate caspase-1 activation and are, hence, the tissue triggers of inflammation in response to infections and/or stressors. The second relies on the ability of certain tissues, and particularly skeletal muscle and adipose tissue, to synthesize and secrete mediators (namely, myokines and adipokines) able to affect, profoundly, the immune function. Physical activity is known to act on both these mechanisms and, hence, its effects on bone are also mediated by the immune system activation. Indeed, that immune system and bone are tightly connected and inflammation is pivotal in determining the bone metabolic status is well-known. The aim of this narrative review is to give a complete view of the exercise-dependent immune system-mediated effects on bone metabolism and function.

Relationships between walking speed, T-score and age with gait parameters in older post-menopausal women with low bone mineral density

BACKGROUND

The gait patterns of women with low bone mineral density (BMD) or osteoporosis have not been thoroughly explored, and when examined, often studied in relation to falls and kyphosis.

RESEARCH QUESTION

The aim of this study was to investigate the relationships between gait parameters and comfortable, self-selected walking speed and BMD in older post-menopausal women with a broad range of T-scores (healthy to osteoporotic).

METHODS

3D kinematic and kinetic data were collected from forty-five women mean (SD) age 67.3 (1.4) years during level walking at their preferred speed. Multiple regression analyses explored the explained variance attributable to speed, femoral neck T-score, and age.

RESULTS

The mean (SD) walking speed 1.40 (0.19) m·s^-1 explained the variance in most temporal-spatial, kinematic and joint powers (R² = 12-68%, P ≤ 0.01). T-score accounted for (R² = 23%, P ≤ 0.001) of the shared explained variance in stride width. It also increased the explanatory power for knee flexion (R² = 7%, P ≤ 0.05) and knee range of motion (R² = 12%, P ≤ 0.01). Power absorption by the knee flexors in terminal swing (K4) was the only power burst resulting in significant slope coefficients for all predictor variables (R² = 52 and 54%) (P ≤ 0.001) and (R² = 68%, P ≤ 0.05).

SIGNIFICANCE

Speed alone explained most of the variance in the gait parameters, while speed and T-score combined increased the explanatory power of the regression models for some of the knee joint variables. Our findings demonstrated that older post-menopausal women, with a broad range of T-scores, are able to walk at comfortably fast speeds, generating gait patterns similar to those of younger women. The results also suggest that strengthening the hip abductor, knee extensor and flexor muscle groups may benefit the gait patterns of older postmenopausal women with low BMD.

Exercise Early and Often: Effects of Physical Activity and Exercise on Women's Bone Health

In 2011 over 1.7 million people were hospitalized because of a fragility fracture, and direct costs associated with osteoporosis treatment exceeded 70 billion dollars in the United States. Failure to reach and maintain optimal peak bone mass during adulthood is a critical factor in determining fragility fracture risk later in life. Physical activity is a widely accessible, low cost, and highly modifiable contributor to bone health. Exercise is especially effective during adolescence, a time period when nearly 50% of peak adult bone mass is gained. Here, we review the evidence linking exercise and physical activity to bone health in women. Bone structure and quality will be discussed, especially in the context of clinical diagnosis of osteoporosis. We review the mechanisms governing bone metabolism in the context of physical activity and exercise. Questions such as, when during life is exercise most effective, and what specific types of exercises improve bone health, are addressed. Finally, we discuss some emerging areas of research on this topic, and summarize areas of need and opportunity.

Distal radius microstructure and finite element bone strain are related to site-specific mechanical loading and areal bone mineral density in premenopausal women

While weight-bearing and resistive exercise modestly increases aBMD, the precise relationship between physical activity and bone microstructure, and strain in humans is not known. Previously, we established a voluntary upper-extremity loading model that assigns a person's target force based on their subject-specific, continuum FE-estimated radius bone strain. Here, our purpose was to quantify the inter-individual variability in radius microstructure and FE-estimated strain explained by site-specific mechanical loading history, and to determine whether variability in strain is captured by aBMD, a clinically relevant measure of bone density and fracture risk. Seventy-two women aged 21–40 were included in this cross-sectional analysis. High resolution peripheral quantitative computed tomography (HRpQCT) was used to measure macro- and micro-structure in the distal radius. Mean energy equivalent strain in the distal radius was calculated from continuum finite element models generated from clinical resolution CT images of the forearm. Areal BMD was used in a nonlinear regression model to predict FE strain. Hierarchical linear regression models were used to assess the predictive capability of intrinsic (age, height) and modifiable (body mass, grip strength, physical activity) predictors. Fifty-one percent of the variability in FE bone strain was explained by its relationship with aBMD, with higher density predicting lower strains. Age and height explained up to 31.6% of the variance in microstructural parameters. Body mass explained 9.1% and 10.0% of the variance in aBMD and bone strain, respectively, with higher body mass indicative of greater density. Overall, results suggest that meaningful differences in bone structure and strain can be predicted by subject characteristics.

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Areal bone mineral density (aBMD) explains 51% of the variability in bone strain.

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Adult bone loading predicts greater cortical porosity and trabecular density.

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Greater body mass predicts greater aBMD and lower bone strain.

Three-dimensional analysis of gait in postmenopausal women with low bone mineral density

Background

There's lack in the literature respecting changes in the trunk and hip angles, and power profile of the lower extremities in postmenopausal women with low bone mineral density (BMD). Therefore, this study aimed to examine gait characteristics of that population, and find out which characteristics may be predictors to BMD. This may provide suitable interventions for subjects with osteoporosis.

Methods

Seventeen healthy postmenopausal women and seventeen with low BMD engaged in this study. Dual X-ray Absorbiometry measured BMD at lumber (L_2–4) and femoral neck. Qualysis gait analysis system assessed the gait pattern of each subject.

Results

Compared to healthy peers, women with low BMD showed less trunk rotation (p = 0.02), hip adduction (p = 0.005) and extension moments (p = 0.008). They showed less hip power generation during early stance (H1S) (p = 0.000), and swing phase (H3S) (p = 0.005), and less hip power absorption (H2S) (p = 0.005). They also, showed less knee power absorption during terminal swing (K4S) (p = 0.002), and ankle power generation at push off (A2S) (p = 0.000). The ability of the gait variables to discriminate between subjects with or without osteopenia was (0.72%, p = 0.016) for trunk rotation, (78%, p = 0.0004) for hip adductor moment, (76%, p = 0.0013) for hip extensor moment, (87%, p < 0.0001) for H1S, (79%, p = 0.0001) for H2S, (77%, p = 0.0008) H3S, (81%, p = 0.0001) for K4S, and (93%, p < 0.0001) for A2S.

Conclusion

Less power generation at the hip and ankle as well as, less power absorption at the hip and knee, may suggest that postmenopausal women with low BMD showed less propulsion, and stability during walking. Trunk rotation, hip adduction and extension moments, H1S, H2S, H3S, K4S, and A2S are significant predictors for low bone mass in the postmenopausal women.

Effects of age-related differences in femoral loading and bone mineral density on strains in the proximal femur during controlled walking

Maintenance of healthy bone mineral density (BMD) is important for preventing fractures in older adults. Strains experienced by bone in vivo stimulate remodeling processes, which can increase or decrease BMD. However, there has been little study of age differences in bone strains. This study examined the relative contributions of age-related differences in femoral loading and BMD to age-related differences in femoral strains during walking using gait analysis, static optimization, and finite element modeling. Strains in older adult models were similar or larger than in young adult models. Reduced BMD increased strains in a fairly uniform manner, whereas older adult loading increased strains in early stance but decreased strains in late stance. Peak ground reaction forces, hip joint contact forces, and hip flexor forces were lower in older adults in late stance phase, and this helped older adults maintain strains similar to those of young adults despite lower BMD. Because walking likely represents a "baseline" level of stimulus for bone remodeling processes, increased strains during walking in older adults might indicate the extent of age-related impairment in bone remodeling processes. Such a measure might be clinically useful if it could be accurately determined with age-appropriate patient-specific loading, geometry, and BMD.

Bone mineral density in the proximal tibia varies as a function of static alignment and knee adduction angular momentum in individuals with medial knee osteoarthritis

Based on the premise that bone mass and bone geometry are related to load history and that subchondral bone may play a role in osteoarthritis (OA), we sought to determine if static and dynamic markers of knee joint loads explain variance in the medial-to-lateral ratio of proximal tibial bone mineral density (BMD) in subjects with mild and moderate medial knee OA. We utilized two surrogate markers of dynamic load, the peak knee adduction moment and the knee adduction angular momentum, the latter being the time integral of the frontal plane knee joint moment. BMD for medial and lateral regions of the proximal tibial plateau and one distal region in the tibial shaft was measured in 84 symptomatic subjects with Kellgren and Lawrence radiographic OA grades of 2 or 3. Utilizing gait analysis, the peak knee adduction moment (the external adduction moment of greatest magnitude) and the time integral of the frontal plane knee joint moment (the angular momentum) over the entire stance phase as well as for each of the four subdivisions of stance were calculated. The BMD ratio was not significantly different in grade 2 (1.32 +/- 0.27) and grade 3 knees (1.47 +/- 0.40) (P = 0.215). BMD of the tibial shaft was not correlated with any loading parameter or static alignment. Of all the surrogate gait markers of dynamic load, the knee adduction angular momentum in terminal stance explained the most variance (20%) in the medial-to-lateral BMD ratio (adjusted r(2) = 0.196, P < 0.001). The knee adduction angular momentum for the entire stance phase explained 18% of the variance in the BMD ratio (adjusted r(2) = 0.178, P < 0.001), 10% more variance than explained by the overall peak knee adduction moment (adjusted r(2) = 0.081, P < 0.001). 18% of the variance in the BMD ratio was also explained by the knee alignment angle (adjusted r(2) = 0.183, P < 0.001), and the total explanatory power was increased to 22% when the knee adduction angular momentum in terminal stance was added (change in r(2) = 0.041, P < 0.05, total adjusted r(2) = 0.215, P < 0.001). The BMD ratio and its relationship to dynamic and static markers of loading were independent of height, weight, and the body mass index, demonstrating that both dynamic markers of knee loading as well as knee alignment explained variance in the tibial BMD ratio independent of body size.