Site-specificity of bone mineral density and muscle strength in women: job-related physical activity

[Impact of osteoporosis on physical performance parameters of middle-aged and elderly individuals-a cross-sectional study]

BACKGROUND

Osteoporosis (OP) in the elderly is accompanied by reduced muscle mass and reduced muscle strength, also known as sarcopenia. This results in functional limitations and a high risk of falls and injuries. The determination of physical performance parameters such as grip strength and trunk strength on the one hand, and balance abilities on the other, provide information about the individual's general neuromuscular condition and serve as an indicator of physical performance in the elderly. The extent to which previous osteoporotic vertebral fractures (VFs) restrict an individual's physical performance has not been adequately investigated yet.

MATERIAL AND METHODS

In total, 118 persons, with a mean age of 71.5 ± 9 years, participated in the clinical trial (ethics committee approval number A2020-0041). Patients were divided into an OP group (58 patients) and a control group (CG; 60 patients). OP patients with (VFs) and without vertebral fractures (0VFs) were viewed separately in the subgroup analysis. Data concerning physical status, including hand grip strength (HGS), the chair-rising test (CRT), tandem stance (TS), tandem gait (TG), and single-leg stance (SLS) were available for all patients. All data were analyzed using SPSS, Version 23.0.

RESULTS

No significant difference (p > 0.05) was registered between the OP and CG groups with regard of HGS, CRT, TG, TS, and SLS. In the subgroup analysis, OP patients with VFs had a lower HGS than OP patients without 0 VFx (VFs 24.3 ± 10.2 kg vs. 0 VFs 29.7 ± 9.5 kg, p = 0.026). TS was maintained longer by OP patients 0 VFs (VFs 7.8 ± 3.2 s vs. 0 VFs 9.5 ± 1.8 s, p = 0.008). The latter were also able to maintain their balance in TG over more numerous steps (VFs 4.8 ± 3.0 vs. 0 VFs 6.7 ± 2.4, p = 0.011). In a regression analysis, body size, gender, and age were shown to be independent factors influencing HGS (p < 0.001).

CONCLUSION

Patient age, constitution, and gender have a relevant influence on HGS, with baseline conditions after diagnosed OP at comparable levels in this age group. In a subgroup of OP patients with VFs, there is a close relationship between bone and muscle with an increasing deterioration of the musculoskeletal system. For prophylaxis of osteosarcopenia, early training seems reasonable.

Measurement and Interpretation of Handgrip Strength for Research on Sarcopenia and Osteoporosis

Handgrip strength (HGS) is associated with several chronic diseases, cognitive decline, length of hospital-stay, and mortality. More importantly, HGS is one of the diagnostic criteria of sarcopenia and gaining attention because of its relevance to bone mineral density (BMD) and osteoporotic fractures. As the measurement of HGS is widely used in clinical practice as well as in research, its accurate measurement and interpretation are becoming more crucial. This review describes how to use different types of dynamometers accurately, the impact of body and arm positions and anthropometric parameters on HGS, the current reference values of HGS for sarcopenia research, and the updates on the relationship between HGS and BMD and osteoporotic fractures.

Relationships between muscle mass, strength and regional bone mineral density in young men

Purpose

Although the relationship between body composition and bone mineral density (BMD) is well established, the relative contribution of appendicular lean mass (ALM) and fat mass (FM) to BMD has been rarely evaluated in young men.

Methods

We assessed 100 young men (age: 24.4±2.8 years, BMI: 23.4±2.81 kg/m²). Appendicular lean mass index (ALM/H²) (ALMI), fat mass index (FM/ H²) (FMI), percentage of body fat, BMD at lumbar spine (LS), total hip (TH), femoral neck (FN) and whole body (WB) were measured using DXA. Muscle strength was evaluated by handgrip strength. Pearson’s correlations and interactions between all variables were assessed using stepwise regression analyses.

Results

ALM index (ALMI) was positively correlated with BMD at all sites (r = 0.62 for WB p<0.05, r = 0.54 for FN p<0.05, r = 0.64 for TH p<0.05, r = 0.56 for LS p<0.05) whereas FMI was not correlated to BMD values. Stepwise regression analyses showed that ALMI produced a significant and positive influence on BMD (β = 0.07 for WB p<0.001, β = 0.04 for FN p<0.001, β = 0.06 for TH p<0.001). Conversely, FMI was negatively associated with BMD at all sites (β = -0.02 for WB p<0.001, β = - 0.03 for FN p<0.001, β = - 0.03 for TH p<0.001, β = - 0.07 for LS p<0.001). Handgrip strength and BMDs were significantly and positively associated at all sites.

Conclusions

Our data suggest that BMD was positively associated with ALMI while negatively with FMI. We confirm that ALMI is the strongest factor associated with BMD in a population of young men.

Toe Gap Force is Related to Ultrasonic Parameter of Calcaneus Bone Status in General Population

Background:

Elucidating the relation between bone health condition and muscle strength can provide useful knowledge for Japan’s super-aged society. This study ascertained the Speed Of Sound (SOS) of the calcaneus and upper and lower limb muscle strength in a general population.

Methods:

Medical examinations were conducted of 277 adult residents (100 men, 177 women; average age 67.1 years) of a mountain village. Bilateral hand grip and hand key pinch strength were measured. Hip abductor muscle strength was measured using a hand-held dynamometer. The pressure between the hallux and second toe (toe-gap force) was measured using a toe pressure measuring instrument. The Speed Of Sound (SOS) of the calcaneus was assessed using an ultrasound bone densitometer. Stepwise linear regression was used to identify the predictor of SOS using several factors as explanatory variables: gender, age, height, weight BMI, grip and key pinch power strength, hip abductor muscle strength, and toe-gap force in bilateral side. P values of < .05 were inferred as statistically significant.

Results:

Significant positive correlation was found between the SOS and each of bilateral hand grip and hand key pinch strength, hip abductor muscle strength, and toe-gap force in all participants. Stepwise logistic regression revealed gender (β coefficient= -0.32, p= .0001), age (β coefficient=-0.53, p= .000), height (β coefficient= -0.19, p= .03), and right toe-gap force (β coefficient= 0.11, p= .027) as predictors of calcaneal SOS for all participants.

Conclusion:

Toe-gap force assessment might be more useful to predict calcaneal SOS than grip assessment in the general population.

Predictors of Bone Status by Quantitative Ultrasound Measurements in a Mountain Village in Japan

Background:

It seems to be important to recognize predictors of bone health condition in Japanese super-aged society. The purpose of this study was to investigate predictors of the speed of sound (SOS) of calcaneus by quantitative ultrasound measurements of mountain village residents.

Materials and Methods:

Medical examinations were conducted on 214 participants (69 men, 145 women; average age of 63.6 years). Each had completed a self-administered questionnaire including items such as gender, dominant hand, occupation, and history of smoking and drinking alcohol, experience of falls, and the EuroQol-5-dimensions-3-level Japanese version and a 25-question geriatric locomotive function scale proposed by the Japanese Orthopaedic Association. Bilateral grip and key pinch strength were measured. The SOS of calcaneus was assessed using ultrasound bone densitometry. Body composition was measured using a multi-frequency segmental body composition analyzer. Spearman's rank correlation coefficient was calculated to elucidate the relation between SOS and evaluation items. Stepwise logistic regression was used to identify predictors of SOS using the investigated factors as explanatory variables. P values of < .05 were regarded as statistically significant.

Results:

Significant positive correlation was found between the SOS and dominant and non-dominant grip and key pinch strength and Euro index and QOL VAS in all participants. In stepwise logistic regression, non-dominant key pinch (β coefficient= 0.27, p= .022) and Euro QOL VAS (β coefficient= 0.24, p= .0001) were predictors of calcaneal SOS for all participants.

Conclusion:

Key pinch strength and Euro QOL VAS assessment might be useful to predict calcaneal SOS in the general population.

Effects of knee extensor muscle strength on the incidence of osteopenia and osteoporosis after 6 years

The association of knee extensor muscle strength with bone mineral density (BMD) has been reported in cross-sectional epidemiological studies, but it remains unclear whether or not this is the case with longitudinal change. Thus, we investigated whether or not the knee extension strength can predict the incidence of osteopenia or osteoporosis after 6 years, then compared the difference between sexes. Subjects were 1255 community-dwelling Japanese men and menopaused women, aged 40-81 years. BMD of lumbar spine and femoral neck was assessed by dual-energy X-ray absorptiometry twice at 6-year intervals. Subjects were divided into three groups, normal, osteopenia, and osteoporosis, depending on their young adult mean BMD % value. In the cross-sectional analysis the correlations between the knee extension strength and BMD of the two regions were examined, using Pearson's correlation coefficient. Longitudinal analyses were then conducted to determine the odds ratio, controlled for age and BMI, given that those who were normal in the initial stage developed osteopenia or osteoporosis after 6 years, for every 1 SD decrease in knee extension strength, as well as those who first had normal or osteopenia and then developed osteoporosis. Cross-sectional analysis showed a statistically significant relation between knee extensor muscle strength and BMD at both the lumbar spine (p = 0.02) and the femoral neck (p < 0.0001) only in men. The longitudinal analysis showed the significant effect of muscle strength on the loss of femoral neck BMD from normal to osteopenia or osteoporosis both in men (OR 1.84, 95 % CI 1.36-2.48, p < 0.0001) and in women (OR 1.29, 95 % CI 1.002-1.65, p < 0.05), as well as on the loss of spinal BMD from normal or osteopenia to osteoporosis only in men (OR 2.97, 95 % CI 1.07-8.23, p < 0.05). The results suggest the importance of knee extension strength to maintain the bone health of the proximal femur and spine in aging particularly in men.

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.

Influence of education, marital status, occupation, and the place of living on skeletal status, fracture prevalence, and the course and effectiveness of osteoporotic therapy in women in the RAC-OST-POL Study

The RAC-OST-POL population-based, epidemiological study provided data concerning the influence of education, marital status, occupation, and the place of living (residence) on skeletal status, fracture prevalence, and the course and effectiveness of osteoporotic therapy in 625 women older than 55 years, all of them recruited from the District of Raciborz in Poland. Their mean age was 66.4 ± 7.8 years. All the women completed a specially designed questionnaire. The skeletal status was assessed by femoral neck (FN) and total hip (TH) densitometry, using a Lunar DPX system (USA). In univariate analyses, taking into consideration the age differences, bone mineralization was dependent on marital status (Z score for FN and TH was significantly higher in widows than in divorcees; p < 0.05), place of residence (better results in rural areas; p < 0.05), and occupation (better in standing than sitting jobs; p < 0.05 for FN Z score and p < 0.01 for TH Z score). The multivariate model allowed us to verify that only place of living and type of occupation had a significant influence on densitometry results. In direct comparison, fracture prevalence seemed to be borderline significantly more common in widows (33.5%) and least common among divorcees (11.8%) (χ(2) = 6.9, df = 3, p = 0.07), but reanalysis performed after age adjustment excluded a true impact of marital status on fracture occurrence. Other factors did not affect fracture occurrence. Some factors influenced the use of medications for osteoporosis: higher level of education was associated with a more frequent use of vitamin D (χ(2) = 8.49, df = 3, p < 0.05) and of hormone replacement therapy (HRT) (χ(2) = 35.7, df = 3, p < 0.00001). HRT was most commonly used by unmarried women (30%) and least commonly by divorcees (11.8%) (χ(2) = 11.7, df = 3, p = 0.01). Vitamin D was more often used among women from the urban area of Raciborz than by those from surrounding rural areas (χ(2) = 9.2, df = 1, p < 0.01). The frequency of use of the three aforementioned medications was associated with the character of occupation. Women with sedentary jobs demonstrated the highest frequency of intake for vitamin D (χ(2) = 9.92, df = 3, p < 0.05) and HRT (χ(2) = 19.48, df = 3, p < 0.001) as well as for other antiresorptive medications (χ(2) = 8.18, df = 3, p < 0.05). We concluded that the results of the epidemiological study demonstrate that both skeletal status and use of antiosteoporotic medications were partially modified by analyzed social factors, whereas fracture prevalence was generally independent from those factors. These data suggest that education, marital status, place of living, and type of occupation may have impacts on implementation of osteoporosis-preventing health programs.

A path model of sarcopenia on bone mass loss in elderly subjects

OBJECTIVE

Aging is associated with decreases in muscle mass, strength, power (sarcopenia) and bone mineral density (BMD). The aims of this study were to investigate in elderly the role of sarcopenia on BMD loss by a path model, including adiposity, inflammation, and malnutrition associations.

METHODS

Body composition and BMD were measured by dual X-ray absorptiometry in 159 elderly subjects (52 male/107 female; mean age 80.3 yrs). Muscle strength was determined with dynamometer. Serum albumin and PCR were also assessed. Structural equations examined the effect of sarcopenia (measured by Relative Skeletal Muscle Mass, Total Muscle Mass, Handgrip, Muscle Quality Score) on osteoporosis (measured by Vertebral and Femoral T-scores) in a latent variable model including adiposity (measured by Total Fat Mass, BMI, Ginoid/Android Fat), inflammation (PCR), and malnutrition (serum albumin).

RESULTS

The sarcopenia assumed a role of moderator in the adiposity-osteoporosis relationship. Specifically, increasing the sarcopenia, the relationship adiposity-osteoporosis (β: -0.58) decrease in intensity. Adiposity also influences sarcopenia (β: -0.18). Malnutrition affects the inflammatory and the adiposity states (β: +0.61, and β: -0.30, respectively), while not influencing the sarcopenia. Thus, adiposity has a role as a mediator of the effect of malnutrition on both sarcopenia and osteoporosis. Malnutrition decreases adiposity; decreasing adiposity, in turn, increase the sarcopenia and osteoporosis.

CONCLUSIONS

This study suggests such as in a group of elderly sarcopenia affects the link between adiposity and BMD, but not have a pure independent effect on osteoporosis.

Muscle strength and bone density in patients with different rheumatic conditions: cross-sectional study

AIM

To explore the relationship between muscle strength and bone density in patients with different rheumatic diseases and to examine whether inflammatory arthritis was more harmful for muscle strength and bone loss than degenerative joint diseases.

METHODS

The study included 361 men and women with a mean±standard deviation age of 60.5±11.4 years and different rheumatic conditions: regional syndromes, osteoarthritis of the hands, shoulders, knees, and hips, and inflammatory arthritis. Maximum voluntary back strength was measured by isometric dynamometry. Bone mineral density (BMD; g/cm2) of the lumbar spine, femoral neck, and distal radius was measured by dual-energy x-ray absorptiometry. Anthropometry and lifestyle characteristics were also assessed.

RESULTS

Back strength was lowest in patients with hand and shoulder osteoarthritis (20.0±17.9 kg), followed by patients with inflammatory arthritis (24.8±19.2 kg). Patients with inflammatory arthritis had the lowest BMD at the mid-radius (0.650±0.115 g/cm2) and femoral neck (0.873±0.137 g/cm2), while patients with hand and shoulder osteoarthritis had the lowest BMD at the mid-radius (0.660±0.101). In both sexes, muscle strength was significantly lower in patients who had lower BMD (T score<-1.0). Multiple regression analysis identified significant predictors of back strength to be spine BMD (P=0.024) and body mass index (P=0.004) in men and femoral neck BMD in women (P=0.004).

CONCLUSION

Muscle strength decline may be connected to bone loss in patients with rheumatic conditions, especially those with inflammatory joint diseases.

Association between lean mass and handgrip strength with bone mineral density in physically active postmenopausal women

The present study evaluated 117 physically active postmenopausal women (67.8+/-7.0yr) who performed neuromotor physical tests (strength, balance, and mobility). Body composition (lean mass [g], fat mass [g], and % fat) and bone mineral density (BMD) of lumbar spine (L1-L4), femoral neck, and total body were measured by dual-energy X-ray absorptiometry. Following the World Health Organization criteria, osteoporosis was found in at least 1 analyzed site in 33 volunteers (28.2%): 30 (25.6%) in lumbar spine and 9 (7.7%) in femoral neck. Body weight was strongly and positively related to BMD in all sites, but the most important component of body composition was lean mass, also significantly related to all BMD sites, whereas fat mass was weakly related to the femoral neck BMD. Percent fat did not correlate with any BMD site. Of all the physical tests, the handgrip strength was most importantly related to lumbar spine, femoral neck, and total body (r=0.49, p<0.001; r=0.56, p<0.001; and r=0.52, p<0.001, respectively). The static body balance presented a weak but significant positive correlation only with lumbar spine. Our results suggest that strategies aiming to improve muscle strength and lean mass must contribute to the bone health of physically active postmenopausal women.

Muscle strength and bone mineral density in mine victims with transtibial amputation

The aims of this study were to: (i) Determine if there were significant bone mineral density and muscle strength differences between intact and amputated limbs, and (ii) investigate the possible relationship between local bone loss and muscle strength in transtibial amputees. Fifteen male veterans with traumatic unilateral transtibial amputations who ranged in age from 18-45 years were included in this prospective study. Lower limb muscle strength was measured with an isokinetic dynamometer. Dual energy X-ray absorptiometry was used to determine bone mineral density of the femur and tibia. The bone mineral density values of the femur and tibia were found significantly decreased on the amputated side. Significant decreases (p < 0.001) in strength of the quadriceps and hamstrings were observed in the amputated limb. There was a weak correlation between quadriceps strength and total femur bone mineral density (p = 0.048, r = 0.518) on the amputated limb. Transtibial amputees are prone to bone mineral loss and muscle strength decrease on the amputated side. Our results also indicate that muscle strength itself might not be of decisive importance for bone mass in transtibial amputees.

Association between moderate physical activity, spinal motion and back muscle strength in postmenopausal women with and without osteoporosis

OBJECTIVE

The purpose of this study was to determine whether physical activity levels of postmenopausal women were associated with their bone mineral density (BMD), back extensor strength (BES), severity of thoracic kyphosis and range of spinal motion.

METHOD

This study adopted a cross-sectional design. 189 female subjects from 50 to 80 years of age were divided into moderately active (n=63) and sedentary (n=126) groups according to their physical activity level, which is measured by the physical activity score. BMD (lumbar spine and hip), BES, severity of thoracic kyphosis and range of spinal motion in the sagittal and frontal plane were measured in each subject.

RESULTS

The groups differed significantly in the range of spinal motion in the sagittal plane (p = 0.01) (moderately active: 26.9 +/- 10.8; sedentary: 23.0 +/- 10.2), as well as in the right frontal plane (p < 0.001) (moderately active: 27.1 +/- 6.4; sedentary: 23.4 +/- 7.5) and left frontal plane (p < 0.001) (moderately active: 27.6 +/- 6.5; sedentary 23.7 +/- 7.4). There were no significant differences in BMD (active: 0.88 +/- 0.18 g/cm2; sedentary: 0.98 +/- 0.15 g/cm2), severity of thoracic kyphosis (active: 52.9 +/- 12.4; sedentary: 51.9 +/- 11.8) or BES (active: 49.0 N +/- 14.6; sedentary: 46.6 N +/- 15.1).

CONCLUSIONS

This study demonstrates that active women had better range of spinal motion than sedentary women, but they did not differ significantly in severity of thoracic kyphosis, BES and BMD.

Low sit-to-stand performance is associated with low femoral neck bone mineral density in healthy women

Bone mass may be adjusted to control the strains produced by muscular activity. We assessed the relationship between maximum rising strength (MRS), a new measurement of sit-to-stand performance, and femoral neck (FN) bone mineral density (BMD), taking into account possible confounding variables. The study population consisted of 249 healthy women aged 18-76. We measured MRS with a dynamometer fixed on the ground and connected by an adjustable nonelastic cord to a padded belt. FN BMD was measured by dual X-ray absorptiometry. Women in the first quartile of FN BMD (<0.702 g/cm(2)) had significantly lower values of MRS, body weight, height, lean mass, past 5-year physical activity expenditures, blood 17 beta estradiol (E2), 25-hydroxyvitamin D (25(OH)D), dehydroepiandrosterone sulfate (DHEAS), and insulin like growth factor 1, and higher values of age and parathyroid hormone than other women. In the logistic regression model, FN BMD values in the lowest quartile were associated with age (adjusted odds ratio [OR(a)] per 10-year increase = 1.84, 95% confidence interval [95% CI] = 1.33-2.54, P < 0.001), body weight (OR(a) per 10-kg decrease = 3.67, 95% CI = 2.08-6.47, P < 0.001), MRS (OR(a) per 20-kg decrease = 1.17, 95% CI = 1.02-1.34, P = 0.03), serum DHEAS (OR(a) < 0.5 mg/ml vs > or =0.5 mg/ml = 2.83, 95% CI = 1.3-6.12, P = 0. 01), and serum E2 (OR(a) per 10-pmol/l decrease = 1.02, 95% CI = 1.01-1.03, P = 0.03). The present study suggests a significant association between low FN BMD and low sit-to-stand performance in healthy women, independent of possible confounding variables.

The role of physical activity in bone health: a new hypothesis to reduce risk of vertebral fracture

Locomotion has always been a major criterion for human survival. Thus, it is no surprise that science supports the dependence of bone health on weight-bearing physical activities. The effect of physical activity on bone is site-specific. Determining how to perform osteogenic exercises, especially in individuals who have osteopenia or osteoporosis, without exceeding the biomechanical competence of bone always poses a dilemma and must occur under medical advice. This article presents the hypothesis that back exercises performed in a prone position, rather than a vertical position, may have a greater effect on decreasing the risk for vertebral fractures without resulting in compression fracture. The risk for vertebral fractures can be reduced through improvement in the horizontal trabecular connection of vertebral bodies.

When are intervertebral discs stronger than their adjacent vertebrae?

STUDY DESIGN

Mechanical testing of cadaveric tissues.

OBJECTIVE

To compare the strength of discs and vertebrae from the same spines in order to determine which are more vulnerable to injury, and to determine how their relative vulnerability depends on age and gender.

SUMMARY OF BACKGROUND DATA

Vertebrae can strengthen and weaken according to mechanical demands, but the avascular intervertebral discs may be unable to "keep up." Little is known about the relative strength of discs and vertebrae.

METHODS

Forty-seven thoracolumbar motion segments were obtained from 30 cadavers 48 to 91 years of age. Each was compressed until a vertebra fractured, and vertebral yield compressive stress (force per unit area) was calculated. Adjacent undamaged intervertebral discs were removed, and circumferential slices, 2.2 mm thick, were cut from the inner, middle, and outer regions of the anterolateral anulus. Slices were stretched to failure to determine their ultimate tensile stress.

RESULTS

Yield compressive stress of male and female vertebrae decreased by 69% and 75%, respectively, in the age range of 48 to 91 years (P < 0.001). In contrast, the ultimate tensile stress of the adjacent anulus did not fall significantly with age, except in the outer region of male discs, where it fell by 66% (P < 0.01). Disc strength was proportional to vertebral strength, but only for the outer anulus, and in male spines (r2= 24%, P = 0.019, n = 22).

CONCLUSION

The outer anulus can adapt to mechanical demands because it is the most metabolically active region of the disc. Disc and bone properties are better matched in male spines because male vertebrae are less affected by variable hormonal changes. The low adaptive potential of intervertebral discs makes them relatively weak in the strengthening spines of young men but relatively strong in the weakening spines of elderly women.

Vertebral body integrity: a review of various anatomical factors involved in the lumbar region

The body of the vertebra can be affected in the majority of the conditions involving the lumbar spine. Multiple references, both books and periodicals, have been reviewed, and the anatomical factors responsible for the vertebral body integrity in the lumbar spine have been included under the following important areas, namely, morphology, development, genetics, microscopic examination using histology, structural architecture, blood supply, neuromuscular control, and biomechanics.

INTRODUCTION

The anatomy provides a three-dimensional frame work to support the interaction between the physiological and pathological alterations. The body of the vertebra can be affected in a majority of acute or chronic conditions involving the lumbar spine. The etiology of these conditions is multifactorial, which has been dealt with in previous studies sporadically. This study aims to review and incorporate the important anatomical factors which can influence the integrity of vertebral bodies in the lumbar region and manifest as low back pain.

METHODS

Multiple references, both books and periodicals, have been reviewed for the literature. Electronic databases, including Medline and PubMed, were used to collect the latest information. They were finally arranged in an anatomical framework for the article. An attempt has been made to cover these relevant issues in an integrated way in the article and have been structured into introduction, morphology, development, genetics, microscopic examination using histology, structural architecture, blood supply, neuromuscular control, biomechanics, and conclusion. The aforementioned anatomical aspects, some of which have received less attention in the literature, may be helpful to clinicians for restoring the mobility, stability, and load bearing capacity of the lumbar spine as well as planning better management strategies, especially for the chronic low back pain.

RESULTS

In our article all the anatomical factors affecting the integrity of vertebral body, including the morphology, development, genetics, growth and ossification, blood supply, specifically in the lumbar region, have been described, which were not covered earlier. The limitations of this review is its wide dimensions; hence, there are fair scopes of missing many relevant facts, as all of them cannot be compiled in a single article. We have attempted to confine our views to different anatomical domains only, this is our second limitation. Additional studies are required to incorporate and discuss the uncovered relevant scientific details.

CONCLUSIONS

The integrity of the body of the lumbar vertebra is multifactorial (Fig. 8). The vast spectrum of the anatomical domain influencing it has been summarized. The evolution of erect posture is a landmark in the morphology of human beings and the lumbar lordosis, which has also contributed to the gross design of the vertebral body, is one of the most important adaptations for axial loading and bipedal movements. The role of metamerism in the evolution of vertebrate morphology is repeated in the development of spine. The body of the vertebra is intersegmental in origin, which results in dual vascular and nerve supply, both from superior and inferior aspects of the body of the lumbar vertebrae. The vertebral body ossifies from three primary centers, one for centrum, which will form the major portion of body, and the other two for neural arches. The cartilaginous growth plate is mainly responsible for the longitudinal vertebral growth. Regional differentiation of the vertebral column, and the definite pattern of the structure of the different vertebra, is regulated by a large number of genetic factors, including the Hox genes. The vertebral body design therefore provides the requirements for optimal load transfer by maximal strength with minimal weight. Bone mineral density (BMD), bone quality, microarchitecture, and material properties are the important factors that contribute to bone strength. BMD is highly heritable; bone mineral distribution and architecture are also shown to be under strong genetic influence. All the aforementioned factors finally integrate to ensure mainly the mobility, stability, and load bearing capacity of the lumbar spine.

Predictive value of grip strength for bone mineral density in males: site specific or systemic?

This study aimed to investigate the predictive role of grip strength on bone mineral density (BMD) of different sites in males. Two hundred thirty-four male patients were included in the study. BMD of lumbar spine, femoral neck, proximal radius-ulna (PRU) and distal radius-ulna (DRU) sites were measured by dual-energy X-ray absorptiometry and grip strength by using a hand dynamometer. Grip strength and BMD values of PRU and DRU at forearms were significantly higher on the dominant sides (P = 0.001, P = 0.001, P = 0.001, respectively). Stepwise linear regression analysis revealed that only the grip strength of the same side was the best predictor of the BMD of the dominant and non-dominant PRU with a ratio of 8.5 and 10.2%, respectively, whereas grip strength of the same side, age and weight were the best predictors of the BMD of the dominant and non-dominant DRU with a ratio of 25 and 24.6%, respectively. There was no predictive value of grip strength for BMD of lumbar spine and femoral neck. In conclusion, grip strength appears to be predictive of site specific rather than systemic BMD.

High-intensity resistance training and postmenopausal bone loss: a meta-analysis

INTRODUCTION

Conflicting evidence exists regarding the optimum exercise for postmenopausal bone loss. A systematic review and meta-analysis was undertaken to evaluate the effects of randomised controlled trials (RCTs) of progressive, high-intensity resistance training on bone mineral density (BMD) amongst postmenopausal women.

METHODS

Structured electronic searching of multiple databases and hand-searching of key journals and reference lists was undertaken to locate relevant studies up to December 2004. Study quality and possible publication bias were assessed using recognised methods. Primary outcomes were absolute changes in BMD at the lumbar spine (LS), femoral neck (FN) and total hip (TH). A priori defined subgroup analyses included concurrent hormonal or antiresorptive therapy or calcium supplementation during the intervention. The weighted mean difference method (WMD) was used for combining study group estimates. Random or fixed effect models were applied according to study heterogeneity observed from the I (2) statistic.

RESULTS

At the LS, 14 RCT study groups were homogenous (I (2)=25.2%) in demonstrating a significant increase (P=0.006) in BMD of 0.006 g/cm(2) (fixed effect; 95% CI 0.002-0.011) following high-intensity resistance training. In contrast, marked heterogeneity (I (2)=88.2%) was apparent within 11 RCT study groups evaluating FN. For this comparison, a random effects model showed a positive change in FN BMD of 0.010 g/cm(2) (95% CI -0.002 to 0.021; P = 0.11). Subgroup analyses showed more anatomical variability of BMD responses to resistance training according to participants' hormone therapy use. Treatment effects for study groups increasing all participants' calcium intake showed significant positive BMD changes at TH (P=0.007). Methodological quality of all included studies was low, and a reporting bias towards studies with positive BMD outcomes was evident.

CONCLUSIONS

These findings are relevant to the nonpharmacological treatment of postmenopausal bone loss.

Relationship between Grip Strength and Hand Bone Mineral Density in Healthy Adults

The aim of this study was to assess site-specific relationship of hand bone mineral density (BMD) with hand size, pinch and grip strength in healthy people aged 19-50 years. A total of 143 healthy volunteers participated in the study (mean age: 34 years). One hundred-six were premenopausal women (mean age: 34 years) and 37 were men (mean age: 34 years). Grip and pinch strength was measured by a Jamar dynamometer (Jamar, Irvington, NY). Second, third and fourth middle phalanx BMD were measured on a MetriScan densitometer (Hayward, CA) and mean value of these three phalanxes were used in the analysis. There was not a significant correlation between hand BMD and grip, pinch strength or hand size in premenopausal women. A significant correlation between hand BMD and grip strength was found in men (right hand; r=0.44, p=0.007, left hand; r=0.33, p=0.05). Hand size was not correlated with hand BMD both in men and in women. The short-term precision for RA was estimated as 0.44%. This is the first report of a site-specific relationship of BMD measured by radiographic absorptiometry with hand size, pinch and grip strength in healthy men and premenopausal women. Our results revealed that there is a moderate correlation between hand-grip strength and hand BMD in men. Hand size does not predict hand BMD both in men and women. Radiographic absorptiometry is a practical and reproducible method to detect bone mineral density of hands and may be a valuable screening tool for osteoporosis.

Differences in thoracic kyphosis and in back muscle strength in women with bone loss due to osteoporosis

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To determine if thoracic kyphosis was different in older women grouped based on their bone mineral density (BMD) and back extensor strength (BES), and to determine if an association between and these variables exist.

SUMMARY OF BACKGROUND DATA

Changes in kyphosis might be related to back extensor weakness in patients with osteoporosis. Disproportionate weakness in back extensor musculature considerably increases the possibility of deformities in the fragile osteoporotic spine.

METHODS

A total of 189 female subjects 50 to 80 years of age were grouped by their BMD and additionally by their BES. All were evaluated for thoracic kyphosis, maximal isometric strength of the back extensors, and BMD of the lumbar spine and the hip.

RESULTS

There was no significant difference in thoracic kyphosis among all groups. Multivariate analyses of BES and BMD showed that only BES might influence thoracic kyphosis (P = 0.02). There was no correlation between BES and BMD. Statistically significant deficit in BES was observed only between the osteoporotic and osteopenic group (P < 0.05). The importance of BES in maintaining posture was observed when the study population was divided according to their BES level. With respect to thoracic kyphosis and BMD values, there were no statistical differences between strong women (BES more than 60 N) and those with medium BES (BES between 60 and 35 N). But the weakest group (BES less then 35 N) had significantly higher (P < 0.05) mean values of thoracic kyphosis in comparison to strong women (BES more than 60 N) and those with medium BES (BES between 60 and 35 N).

CONCLUSION

The severity of thoracic kyphosis may be influenced especially by changes in BES. Therefore, provision of strong, natural extrinsic support for the spine seems to be important to decrease the incidence of spinal deformity.

Relationships between muscle strength and bone mineral density of three body regions in sedentary postmenopausal women

This cross-sectional study was designed to investigate correlations between muscle strength and regional bone mineral density (BMD) in sedentary postmenopausal women. Sixty-two women who ranged in age from 41 to 76 years were investigated. Hip and trunk muscle strength was measured by isokinetic dynamometry. Grip strength of the nondominant hand was measured using a hand-held dynamometer. Bone mineral density of the lumbar spine, femur, and distal radius was measured by dual-energy X-ray absorptiometry. Only the correlation between hip abductor strength and femoral BMD was significant (P = 0.009, r = 0.327). There was no correlation between trunk muscle strength and lumbar vertebral BMD or between grip strength and distal radius BMD. Subjects with osteoporosis (T score < -2.5) or osteopenia T (-2.5 to -1) and normal subjects (T > -1) exhibited similar isokinetic hip and trunk muscle strength. Women with osteoporotic distal radii had significantly lower grip strength than subjects who were osteopenic or normal at this site, but the osteoporotic group was also significantly older. In conclusion, our results indicate that the isokinetic strength of hip abductors weakly correlates with femoral BMD in postmenopausal women with and without osteoporosis. Trunk muscle strength did not correlate with lumbar vertebral BMD in either of these groups. The weaker handgrip we observed in the women with osteoporotic radii may be attributed to older age.

Site specificity of regular health club exercise on muscle strength, fitness, and bone density in women aged 29 to 45 years

OBJECTIVE

To determine the effect of regular exercise with use of stepper or skier machines on muscle strength, cardiovascular fitness, bone mineral density, and markers of bone turnover in women aged 29 to 45 years.

SUBJECTS AND METHODS

We evaluated 14 women: 5 who used a stepper machine for at least 3 hours each week for 2 years, 4 who used a skier machine for at least 3 hours each week for 2 years, and 5 who did not exercise (controls). All women were healthy, had no history of disease or medication use known to affect bone metabolism, and had normal levels of estradiol-17beta. Differences between the exercise and control groups were analyzed with the Kruskal-Wallis test.

RESULTS

No significant differences were noted between the exercise groups and the control group with respect to age, height, total body bone mineral density, calcium intake, and metabolic bone markers. Significant differences were noted between the groups in body weight (stepper vs control, P=.03; skier vs control, P=.02), body mass index (stepper vs control, P=.03; skier vs control, P=.02), Physical Activity Score (stepper vs control, P=.009; skier vs control, P=.01), percentage body fat (stepper vs control, P=.03; skier vs control, P=.02), and maximum oxygen consumption (stepper vs control, P=.009; skier vs control, P=.009). Bilateral hip extensor strength was significantly stronger in the stepper group than in the skier group (P=.03). Grip strength was significantly stronger in the stepper group than in the skier group (right, P=.01; left, P=.049).

CONCLUSION

Although comparable health club exercises can contribute to fitness, their site-specific effect varies. Stepper machines are preferred over skier machines for improving hip extensor strength.

A review of anatomical and mechanical factors affecting vertebral body integrity

Background: The aetiology of osteoporotic vertebral fracture is multifactorial and may be conceptualised using a systems framework. Previous studies have established several correlates of vertebral fracture including reduced vertebral cross-sectional area, weakness in back extensor muscles, reduced bone mineral density, increasing age, worsening kyphosis and recent vertebral fracture. Alterations in these physical characteristics may influence biomechanical loads and neuromuscular control of the trunk and contribute to changes in subregional bone mineral density of the vertebral bodies. Methods: This review discusses factors that have received less attention in the literature, which may contribute to the development of vertebral fracture. A literature review was conducted using electronic databases including Medline, Cinahl and ISI Web of Science to examine the potential contribution of trabecular architecture, subregional bone mineral density, vertebral geometry, muscle force, muscle strength, neuromuscular control and intervertebral disc integrity to the aetiology of osteoporotic vertebral fracture. Interpretation: A better understanding of factors such as biomechanical loading and neuromuscular control of the trunk may help to explain the high incidence of subsequent vertebral fracture after sustaining an initial vertebral fracture. Consideration of these issues may be important in the development of prevention and management strategies.

Lower extremity muscle strength does not independently predict proximal femur bone mineral density in healthy older adults

The relationship described in the published literature between muscle strength and bone mineral density of older adults is not entirely certain. It is possible that the direct relationship reported in some studies is biased by failing to mathematically account for the biological influence of body weight and body height on both bone mineral density and muscle strength. This study sought to determine if the relationships between measures of lower extremity muscle strength and bone mineral density of the proximal femur are independent of body size (i.e., body height and body weight) in healthy older adults. We recruited 50 older women and 29 older men, all of whom were healthy community dwellers and not involved in resistance training. Quantitative analysis of the isometric strength of the bilateral ankle, knee, and hip joints and assessment of bone mineral density of the proximal femur were conducted. Muscle strength values were adjusted for the influence of body height and body weight using an allometric scaling procedure. The correlations between proximal femur bone mineral density and the unadjusted strength values were weak but statistically significant. After adjusting muscle strength to account for the influence of body height and body weight, the magnitudes of the correlations between bone mineral density and muscle strength diminished substantially and were not significantly different from zero. The results reveal that, for a typical sample of healthy older adults not involved in resistance training, the relationship between maximal isometric muscle strength of lower extremity joints and proximal femur bone mineral density is reliant on body size.

Race and sex effects on the association between muscle strength, soft tissue, and bone mineral density in healthy elders: the Health, Aging, and Body Composition Study

Two factors generally reported to influence bone density are body composition and muscle strength. However, it is unclear if these relationships are consistent across race and sex, especially in older persons. If differences do exist by race and/or sex, then strategies to maintain bone mass or minimize bone loss in older adults may need to be modified accordingly. Therefore, we examined the independent effects of bone mineral-free lean mass (LM), fat mass (FM), and muscle strength on regional and whole body bone mineral density (BMD) in a cohort of 2,619 well-functioning older adults participating in the Health, Aging, and Body Composition (Health ABC) Study with complete measures. Participants included 738 white women, 599 black women, 827 white men, and 455 black men aged 70-79 years. BMD (g/cm2) of the femoral neck, whole body, upper and lower limb, and whole body and upper limb bone mineral-free LM and FM was assessed by dual-energy X-ray absorptiometry (DXA). Handgrip strength and knee extensor torque were determined by dynamometry. In analyses stratified by race and sex and adjusted for a number of confounders, LM was a significant (p < 0.001) determinant of BMD, except in white women for the lower limb and whole body. In women, FM also was an independent contributor to BMD at the femoral neck, and both FM and muscle strength contributed to limb BMD. The following were the respective beta-weights (regression coefficients for standardized data, Std beta) and percent difference in BMD per unit (7.5 kg) LM: femoral neck, 0.202-0.386 and 4.7-5.9%; lower limb, 0.209-0.357 and 2.9-3.5%; whole body, 0.239-0.484 and 3.0-4.7%; and upper limb (unit = 0.5 kg), 0.231-0.407 and 3.1-3.4%. Adjusting for bone size (bone mineral apparent density [BMAD]) or body size BMD/height) diminished the importance of LM, and the contributory effect of FM became more pronounced. These results indicate that LM and FM were associated with bone mineral depending on the bone site and bone index used. Where differences did occur, they were primarily by sex not race. To preserve BMD, maintaining or increasing LM in the elderly would appear to be an appropriate strategy, regardless of race or sex.

Body composition predicts bone mineral density and balance in premenopausal women

Low bone mineral density (BMD) and poor stability both contribute to increased risk of fractures associated with a fall. Our aim in this cross-sectional study was to determine the anthropometric and/or performance variables that best predicted BMD and stability in women. BMD, body composition, muscle strength, muscle power, and dynamic stability were evaluated in 61 women (age 40 +/- 4 years; % body fat 27% +/- 5%). In correlation analyses, BMD at all sites was significantly related to height, lean mass, strength, and leg power (r2 = 0.25-0.49). Significant inverse relationships were found between all independent variables and dynamic stability (r2 = 0.23-0.52). In stepwise regression, lean mass independently predicted BMD at the femoral neck (R2 = 0.20), total hip (R2 = 0.24), and whole body (R2 = 0.17), whereas hip abductor torque predicted 23% of the variance in trochanter BMD and added 6% to the variance in total hip BMD. Leg power was the only predictor of spine BMD (R2 = 0.14). Fat and lean mass both independently predicted poor performance on postural stability, with fat mass contributing 31% of the total variance (R2 = 0.38). In conclusion, we found lean mass to be a robust predictor of BMD in premenopausal women. Furthermore, both hip abductor torque and leg power independently predicted BMD at clinically relevant fracture sites (hip and spine). The finding that higher fat mass contributes to the majority of the variance in poor stability indicates that greater fat mass may compromise stability and, thus, increase fall risk in heavier individuals.

The relation between stress fractures and bone mineral density: evidence from active-duty Army women

OBJECTIVE

To determine if bone mineral density (BMD) is associated with the probability of stress fractures in premenopausal women.

DESIGN

Case-control study.

SETTING

Large Army post, Fort Lewis, WA.

PARTICIPANTS

Twenty-seven active duty Army women with documented stress fractures within the last 2 years and 158 female controls.

METHODS AND MAIN RESULTS

All subjects were examined and interviewed. BMD of the femoral neck and posteroanterior lumbar spine (L2-L4) was measured using dual energy X-ray absorptiometry. Univariate comparisons revealed no significant differences in BMD of the femoral neck or lumbar spine between groups. Women with stress fractures had a significantly higher exercise intensity (428 vs 292 minutes per week, p<.05) and were more likely to be entry-level enlisted soldiers (63% vs. 44%, p<.05) than those without stress fractures. Multivariate analyses revealed a strong negative association between femoral neck BMD and the probability of stress fractures (lower BMD, higher risk). Exercise intensity and body mass index had a significant positive effect on BMD of the femoral neck and lumbar spine, yet both were associated with an increased probability of stress fractures.

CONCLUSIONS

Femoral neck BMD was significantly associated with the probability of stress fractures. Optimal training programs should balance the beneficial indirect effect of increased exercise (through increased BMD) with its detrimental direct effect on stress fractures.