Understanding falls in osteoporosis: the viscoelastic modeling perspective

Comparative study on muscle-tendon stiffness and balance impairment in postmenopausal women: a focus on osteosarcopenia and osteoporosis

BACKGROUND AND AIMS

This study set out to examine the stiffness of the gastrocnemius medialis (GM) and Achilles tendon across postmenopausal women with osteosarcopenia (OS), osteoporosis (OP), and normal bone mineral density. Furthermore, we explored the relationship between muscle-tendon stiffness and postural sway during a curve-tracking task in both sagittal (AP) and frontal (ML) planes.

METHODS

Seventy-three women volunteered to participate in this study. The participants were classified into OS (T-score ≤ - 2.5 and muscle mass below 5.5 kg/m2), OP (T-score ≤ - 2.5), and healthy (T-score >-1) groups. The shear wave elastography was used to determine GM and Achilles tendon stiffness during rest and activation. The postural sway was recorded using a force plate during the performance-based curve tracking (CT) task.

RESULTS

The stiffness of the GM and Achilles tendon was found to be significantly lower in the OS group compared to the OP and healthy groups (P < 0.05). In the CT task, the OS group exhibited a significant decrease in the mean absolute (P = 0.011) and RMS error (P = 0.022) in the ML direction compared to the OP group. Additionally, a positive correlation was found between the ML mean absolute error and both GM and Achilles's stiffness during rest and activation (P < 0.05).

DISCUSSION AND CONCLUSION

The OS group exhibited the lowest muscle-tendon stiffness. The GM and Achilles stiffness was positively correlated with poor performance-based balance, particularly in the ML direction. This may increase the risk of falls and subsequent hip fractures during simple daily weight- shifting activities in women with osteosarcopenia.

Characterization of Postural Sway in Women with Osteoporosis and a Control Group by Means of Linear and Nonlinear Methods

The mechanisms underlying the altered postural control and risk of falling in patients with osteoporosis are not yet fully understood. The aim of the present study was to investigate postural sway in women with osteoporosis and a control group. The postural sway of 41 women with osteoporosis (17 fallers and 24 non-fallers) and 19 healthy controls was measured in a static standing task with a force plate. The amount of sway was characterized by traditional (linear) center-of-pressure (COP) parameters. Structural (nonlinear) COP methods include spectral analysis by means of a 12-level wavelet transform and a regularity analysis via multiscale entropy (MSE) with determination of the complexity index. Patients showed increased body sway in the medial–lateral (ML) direction (standard deviation in mm: 2.63 ± 1.00 vs. 2.00 ± 0.58, p = 0.021; range of motion in mm: 15.33 ± 5.58 vs. 10.86 ± 3.14, p = 0.002) and more irregular sway in the anterior–posterior (AP) direction (complexity index: 13.75 ± 2.19 vs. 11.18 ± 4.44, p = 0.027) relative to controls. Fallers showed higher-frequency responses than non-fallers in the AP direction. Thus, postural sway is differently affected by osteoporosis in the ML and AP directions. Clinically, effective assessment and rehabilitation of balance disorders can benefit from an extended analysis of postural control with nonlinear methods, which may also contribute to the improvement of risk profiles or a screening tool for the identification of high-risk fallers, thereby prevent fractures in women with osteoporosis.

Are weight shifting and dynamic control strategies different in postmenopausal women with and without type-I osteoporosis?

OBJECTIVE

Tracking postural control processes at dynamic conditions might help develop an appropriate rehabilitation program in osteoporotic women. This study aimed to investigate the differences in center of pressure (COP) control at weight shifting and dynamic tasks between postmenopausal women with and without type-I osteoporosis. Also, we investigated the correlations between bone mineral density (BMD), the activity-specific balance confidence questionnaire (ABC-Q) score, and postural control parameters.

METHOD

A total of 62 volunteer postmenopausal women participated in this study. The participants were classified into non-osteoporotic (NOP, T-score >1, n = 35, age = 60.04± 5.33 years) and osteoporotic (OP, T-score < -2.5, n = 27, age = 61.88 ± 5.34 years) groups. The COP sway was recorded using a Kistler force plate during performance-based Limits of Stability (LOS), Curve Tracking (CT), Sit to Stand (STS), and Turn tasks. In addition, the level of balance confidence in daily activities was evaluated by ABC-Q.

RESULTS

In the LOS task, COP sway velocity in the anterior direction (P = 0.02) and COP maximum excursion in the side-to-side direction (right-side P = 0.027 and left-side P = 0.044) were significantly lower in the OP than the NOP group. In the CT task, all the quantified parameters, including errors and area, showed significantly lower values in the OP group than the NOP group (P < 0.05). In the STS task, the rising index score was significantly higher in the OP group than the NOP group (P = 0.014). The two groups had an equal ABC-Q score (P = 0.175). The COP sway variables correlated significantly with the lumbar and femoral neck T-score (P < 0.05).

CONCLUSION

BMD decline can change weight shifting and dynamic postural control in postmenopausal women.

Comparing Machine Learning Methods to Improve Fall Risk Detection in Elderly with Osteoporosis from Balance Data

Falls are a multifactorial cause of injuries for older people. Subjects with osteoporosis are particularly vulnerable to falls. We study the performance of different computational methods to identify people with osteoporosis who experience a fall by analysing balance parameters. Balance parameters, from eyes open and closed posturographic studies, and prospective registration of falls were obtained from a sample of 126 community-dwelling older women with osteoporosis (age 74.3 ± 6.3) using World Health Organization Questionnaire for the study of falls during a follow-up of 2.5 years. We analyzed model performance to determine falls of every developed model and to validate the relevance of the selected parameter sets. The principal findings of this research were (1) models built using oversampling methods with either IBk (KNN) or Random Forest classifier can be considered good options for a predictive clinical test and (2) feature selection for minority class (FSMC) method selected previously unnoticed balance parameters, which implies that intelligent computing methods can extract useful information with attributes which otherwise are disregarded by experts. Finally, the results obtained suggest that Random Forest classifier using the oversampling method to balance the data independent of the set of variables used got the best overall performance in measures of sensitivity (>0.71), specificity (>0.18), positive predictive value (PPV >0.74), and negative predictive value (NPV >0.66) independent of the set of variables used. Although the IBk classifier was built with oversampling data considering information from both eyes opened and closed, using all variables got the best performance (sensitivity >0.81, specificity >0.19, PPV = 0.97, and NPV = 0.66).

Posturography Comparison and Discriminant Analysis Between Individuals With and Without Chronic Low Back Pain

OBJECTIVE

The aims of this study were to evaluate the center of pressure (CoP) in individuals with chronic low back pain (LBP) compared with matched controls and perform discriminant analysis to detect which CoP variables differentiate the groups.

METHODS

Thirty-two participants with LBP and 33 matched controls were evaluated on a force plate in a bipedal static position for 30 seconds in 2 conditions: eyes open (EO) and eyes closed (EC). Two discriminant analyzes were performed to detect which CoP variables could discriminate between groups.

RESULTS

Those with LBP had higher values (ie, poorer balance) for most variables compared with the control group. With EO, total displacement of sway (TDS) was as follows: LBP group (median [25%-75%]) 31.77 (26.39-41.79) cm, control group 27.21 (22.29-31.78) cm, P = .008 and area: LBP group 3.31 (2.33-4.68) cm², control group 1.77 (1.3-2.71) cm². With EC, TDS was as follows: LBP group 49.6 (39.65-68.15) cm, control group 38.77 (30.36; 45.65) cm, P = .003 and area: LBP group 4.68 (2.6-7.28) cm², control group 2.4 (2.1-3.34) cm². The discriminating variables in the EO condition were the TDS for the LBP group and the anteroposterior mean velocity for the control group, while in the EC condition they were mediolateral dispersion and area for the LBP group.

CONCLUSION

Individuals with chronic LBP had worse postural control performance than matched controls, and it is possible to characterize those with and without LBP with CoP variables.

Autoregressive modeling to assess stride time pattern stability in individuals with Huntington's disease

Background

Huntington’s disease (HD) is a progressive, neurological disorder that results in both cognitive and physical impairments. These impairments affect an individual’s gait and, as the disease progresses, it significantly alters one’s stability. Previous research found that changes in stride time patterns can help delineate between healthy and pathological gait. Autoregressive (AR) modeling is a statistical technique that models the underlying temporal patterns in data. Here the AR models assessed differences in gait stride time pattern stability between the controls and individuals with HD. Differences in stride time pattern stability were determined based on the AR model coefficients and their placement on a stationarity triangle that provides a visual representation of how the patterns mean, variance and autocorrelation change with time. Thus, individuals who exhibit similar stride time pattern stability will reside in the same region of the stationarity triangle. It was hypothesized that individuals with HD would exhibit a more altered stride time pattern stability than the controls based on the AR model coefficients and their location in the stationarity triangle.

Methods

Sixteen control and twenty individuals with HD performed a five-minute walking protocol. Time series’ were constructed from consecutive stride times extracted during the protocol and a second order AR model was fit to the stride time series data. A two-sample t-test was performed on the stride time pattern data to identify differences between the control and HD groups.

Results

The individuals with HD exhibited significantly altered stride time pattern stability than the controls based on their AR model coefficients (AR1 p < 0.001; AR2 p < 0.001).

Conclusions

The AR coefficients successfully delineated between the controls and individuals with HD. Individuals with HD resided closer to and within the oscillatory region of the stationarity triangle, which could be reflective of the oscillatory neuronal activity commonly observed in this population. The ability to quantitatively and visually detect differences in stride time behavior highlights the potential of this approach for identifying gait impairment in individuals with HD.

Relationship between core stability and dynamic balance in women with postmenopausal osteoporosis

Objectives

The aim of this study was to investigate the relationship between core stability and dynamic balance in women with postmenopausal osteoporosis.

Patients and methods

A total of 100 females (mean age 59.9±7.5 years; range, 42 to 73 years) with postmenopausal osteoporosis between January 2016 and June 2016 were included in this study. All patients were evaluated for dynamic balance with the Star Excursion Balance Test (SEBT) and for core stability with trunk flexion, extension, and Side Bridge Test (SBT).

Results

There was a significant correlation between age and the reach directions of anterior (A), posteromedial (PM), and posterolateral (PL) of the right limb (p<0.001, p=0.009, p=0.012) and the reach directions of A and PM of the left limb (p<0.001, p=0.004). There was no correlation between the lumbar spine, femoral neck, and total hip Bone Mineral Density (BMD) and the reach directions of SEBT (p>0.05). There was a significant correlation between the trunk flexion test results and the reach directions of A, PM, and PL of the right limb (p=0.005, p=0.001, p=0.002), (r=0.277, r=0.333, r=0.308) and the reach directions of A, PM, and PL of the left limb (p=0.008, p=0.016, p=0.005), (r=0.265, r=0.239, r=0.276). There was a significant correlation between the SBT results and the reach directions of A, PM, and PL of the right limb (p<0.001, p<0.001, p=0.005), (r=0.423, r=0.366, r=0.281) and the reach directions of A, PM, and PL of the left limb (p<0.001, p<0.001, p=0.001), (r=0.418, r=0.356, r=0.316). There was a significant correlation between the trunk extension test results and the reach directions of A, PM, and PL of the right limb (p<0.001, p<0.001, p=0.006), (r=0.383, r=0.471, r=0.276) and the reach directions of A, PM, and PL of the left limb (p<0.001, p<0.001, p=0.003) (r=0.407, r=0.401, r=0.297).

Conclusion

Our study results showed that age and core stability were associated with dynamic balance in women with postmenopausal osteoporosis.

Serum 25-hydroxyvitamin D levels are associated with functional capacity but not with postural balance in osteoporotic postmenopausal women

OBJECTIVES:

In post-menopausal women with osteoporosis, insufficient vitamin D levels decrease calcium fixation in the bones and calcium transport in the sarcoplasmic reticulum, which impairs muscle strength, possibly leading to detrimental consequences for the preservation of functional capacity and postural balance, fall prevention, and fracture risk. The aim of this study was to evaluate the association between vitamin D levels and knee muscle strength, postural balance and functional mobility among postmenopausal women with osteoporosis.

METHODS:

This cross-sectional study included 63 osteoporotic older women (aged 60.6±3.1 years). The subjects completed the Timed Up and Go Test to measure functional mobility, and postural balance was assessed on the AccuSway Plus portable force platform. Maximal strength was tested using an isokinetic dynamometer for knee flexion and extension. The subjects were assessed as a group and were divided into quartiles according to their vitamin D levels. Clinicaltrials.gov: NCT02771834.

RESULTS:

Vitamin D status was independently associated with the normalized peak torque of the knee extensors (β=0.59; p=0.04) and Timed Up and Go Test (β=-0.07; p<0.001). No between-group differences were observed in the demographic and clinical variables or postural balance; however, significant differences were observed in the Timed Up and Go Test, and the group with the highest vitamin D levels exhibited better performance than the group with the lowest vitamin D levels (p<0.001).

CONCLUSION:

The serum vitamin D levels were independently associated with normalized knee extension strength and functional mobility in postmenopausal women with osteoporosis.

The effect of single-task and dual-task balance exercise programs on balance performance in adults with osteoporosis: a randomized controlled preliminary trial

Osteoporosis is a serious disease characterized by muscle weakness in the lower extremities, shortened length of trunk, and increased dorsal kyphosis leading to poor balance performance. Although balance impairment increases in adults with osteoporosis, falls and fall-related injuries have been shown to occur mainly during the dual-task performance. Several studies have shown that dual-task performance was improved with specific repetitive dual-task exercises.

INTRODUCTION

The aims of this study were to compare the effect of single- and dual-task balance exercise programs on static balance, dynamic balance, and activity-specific balance confidence in adults with osteoporosis and to assess the effectiveness of dual-task balance training on gait speed under dual-task conditions.

METHODS

Older adults (N = 42) (age range, 45-88 years) with osteoporosis were randomly assigned into two groups. Single-task balance training group was given single-task balance exercises for 4 weeks, whereas dual-task balance training group received dual-task balance exercises. Participants received 45-min individualized training session, three times a week. Static balance was evaluated by one-leg stance (OLS) and a kinesthetic ability trainer (KAT) device. Dynamic balance was measured by the Berg Balance Scale (BBS), Time Up and Go (TUG) test, and gait speed. Self-confidence was assessed with the Activities-specific Balance Confidence (ABC-6) scale. Assessments were performed at baseline and after the 4-week program.

RESULTS

At the end of the treatment periods, KAT score, BBS score, time in OLS and TUG, gait speeds under single- and dual-task conditions, and ABC-6 scale scores improved significantly in all patients (p < 0.05). However, BBS and gait speeds under single- and dual-task conditions showed significantly greater improvement in the dual-task balance training group than in the single-task balance training group (p < 0.05). ABC-6 scale scores improved more in the single-task balance training group than in the dual-task balance training group (p < 0.05).

CONCLUSIONS

A 4-week single- and dual-task balance exercise programs are effective in improving static balance, dynamic balance, and balance confidence during daily activities in older adults with osteoporosis. However, single- and dual-task gait speeds showed greater improvement following the application of a specific type of dual-task exercise programs.

CLINICAL TRIAL REGISTRATION NUMBER

24102014-2.

Eldecalcitol improves muscle strength and dynamic balance in postmenopausal women with osteoporosis: an open-label randomized controlled study

The antifracture efficacy of vitamin D in osteoporosis is due to its direct action on bones and indirect extraskeletal effects to prevent falls. Eldecalcitol is an analog of active vitamin D3 that improves bone mineral density and reduces the risk of osteoporotic fractures. However, the effects of eldecalcitol on muscle strength and static and dynamic postural balance are unclear. In this open-label randomized controlled study, we assessed the effects of eldecalcitol on muscle strength and static and dynamic postural balance in 50 postmenopausal women (mean age 74 years) with osteoporosis treated with bisphosphonate. Participants were randomly divided into a bisphosphonate group (alendronate at 35 mg/week; n = 25) or an eldecalcitol group (eldecalcitol at 0.75 μg/day and alendronate at 35 mg/week; n = 25) and were followed up for 6 months. Trunk muscle strength, including back extensor strength and iliopsoas muscle strength, was measured. Static standing balance was evaluated and the one leg standing test was performed to assess static postural balance. Dynamic sitting balance was evaluated and the 10-m walk test, functional reach test, and timed up and go test were performed to assess dynamic postural balance. At 6 months, there were no significant changes in any measure of muscle strength or balance in the bisphosphonate group, whereas eldecalcitol significantly increased back extensor strength (p = 0.012) and iliopsoas muscle strength (p = 0.035). Eldecalcitol also significantly improved findings on the timed up and go test (p = 0.001) and dynamic sitting balance (p = 0.015) at 6 months. These results with eldecalcitol may have an impact on prevention of falls.

Balance Maintenance in the Upright Body Position: Analysis of Autocorrelation

The present research aimed to analyze values of the autocorrelation function measured for different time values of ground reaction forces during stable upright standing. It was hypothesized that if recording of force in time depended on the quality and way of regulating force by the central nervous system (as a regulator), then the application of autocorrelation for time series in the analysis of force changes in time function would allow to determine regulator properties and its functioning. The study was performed on 82 subjects (students, athletes, senior and junior soccer players and subjects who suffered from lower limb injuries). The research was conducted with the use of two Kistler force plates and was based on measurements of ground reaction forces taken during a 15 s period of standing upright while relaxed. The results of the autocorrelation function were statistically analyzed. The research revealed a significant correlation between a derivative extreme and velocity of reaching the extreme by the autocorrelation function, described as gradient strength. Low correlation values (all statistically significant) were observed between time of the autocorrelation curve passing through 0 axis and time of reaching the first peak by the said function. Parameters computed on the basis of the autocorrelation function are a reliable means to evaluate the process of flow of stimuli in the nervous system. Significant correlations observed between the parameters of the autocorrelation function indicate that individual parameters provide similar properties of the central nervous system.

Characteristics of Autocorrelation Structure of Lower Extremity Functional Laterality in Disturbed and Undisturbed Bipedal Upright Stance

Purpose. It is posited that functional laterality is influenced by the generation and conduction of neural signals and therefore associated with sensorimotor control. The question arises if symmetry or asymmetry in sensorimotor processing affects the development of symmetric or asymmetric motor programs in the lower extremities. The purpose of the study was to examine the mechanisms of the human mobility moto-control - the process of maintaining body balance in a standing position through an appropriate course of distribution of ground reaction forces in a time frame, in a situation requiring lower extremity movement symmetry. Methods. The autocorrelation function was calculated for ground reaction forces (in the three orthogonal axes) registered during 45 s of bipedal upright stance in two conditions (eyes open and closed). Results. Minor albeit significant deficiencies in postural muscle control were revealed as a function of time, as evidenced in the decay of the autocorrelation function to zero (T

Load Dependency of Postural Control--Kinematic and Neuromuscular Changes in Response to over and under Load Conditions

Introduction

Load variation is associated with changes in joint torque and compensatory reflex activation and thus, has a considerable impact on balance control. Previous studies dealing with over (OL) and under loading (UL) used water buoyancy or additional weight with the side effects of increased friction and inertia, resulting in substantially modified test paradigms. The purpose of this study was to identify gravity-induced load dependency of postural control in comparable experimental conditions and to determine the underlying neuromuscular mechanisms.

Methods

Balance performance was recorded under normal loading (NL, 1g), UL (0.16g; 0.38g) and OL (1.8g) in monopedal stance. Center of pressure (COP) displacement and frequency distribution (low 0.15-0.5Hz (LF), medium 0.5-2Hz (MF), high 2-6Hz (HF)) as well as ankle, knee and hip joint kinematics were assessed. Soleus spinal excitability was determined by H/M-recruitment curves (H/M-ratios).

Results

Compared to NL, OL caused an increase in ankle joint excursion, COP HF domain and H/M-ratio. Concomitantly, hip joint excursion and COP LF decreased. Compared to NL, UL caused modulations in the opposite direction: UL decreased ankle joint excursions, COP HF and H/M-ratio. Collaterally, hip joint excursion and COP LF increased. COP was augmented both in UL and in OL compared to NL.

Conclusion

Subjects achieved postural stability in OL and UL with greater difficulty compared to NL. Reduced postural control was accompanied by modified balance strategies and compensatory reflex activation. With increasing load, a shift from hip to ankle strategy was observed. Accompanying, COP frequency distribution shifted from LF to HF and spinal excitability was enhanced. It is suggested that in OL, augmented ankle joint torques are compensated by quick reflex-induced postural reactions in distal muscles. Contrarily, UL is associated with diminished joint torques and thus, postural equilibrium may be controlled by the proximal segments to adjust the center of gravity above the base of support.

Mechanical Impedance and Its Relations to Motor Control, Limb Dynamics, and Motion Biomechanics

The concept of mechanical impedance represents the interactive relationship between deformation kinematics and the resulting dynamics in human joints or limbs. A major component of impedance, stiffness, is defined as the ratio between the force change to the displacement change and is strongly related to muscle activation. The set of impedance components, including effective mass, inertia, damping, and stiffness, is important in determining the performance of the many tasks assigned to the limbs and in counteracting undesired effects of applied loads and disturbances. Specifically for the upper limb, impedance enables controlling manual tasks and reaching motions. In the lower limb, impedance is responsible for the transmission and attenuation of impact forces in tasks of repulsive loadings. This review presents an updated account of the works on mechanical impedance and its relations with motor control, limb dynamics, and motion biomechanics. Basic questions related to the linearity and nonlinearity of impedance and to the factors that affect mechanical impedance are treated with relevance to upper and lower limb functions, joint performance, trunk stability, and seating under dynamic conditions. Methods for the derivation of mechanical impedance, both those for within the system and material-structural approaches, are reviewed. For system approaches, special attention is given to methods aimed at revealing the correct and sufficient degree of nonlinearity of impedance. This is particularly relevant in the design of spring-based artificial legs and robotic arms. Finally, due to the intricate relation between impedance and muscle activity, methods for the explicit expression of impedance of contractile tissue are reviewed.

Balance control in elderly people with osteoporosis

Osteoporosis is a prevalent health concern among older adults and is associated with an increased risk of falls that incur fracture, injury, or mortality. Identifying the risk factors of falls within this population is essential for the development of effective regimes for fall prevention. Studies have shown that muscle quality and good posture alignments are critical for balance control in elderly individuals. People with osteoporosis often have muscle weakness and increased spine kyphosis leading to vertebral fractures and poor balance control, or even falls. Therefore, improving muscle quality, strengthening weak muscles, and correcting postural alignment are essential elements for the prevention of falls and fractures in older adults with osteoporosis. This review reports the necessary information regarding the critical factors of balance control in older adults with osteoporosis, as well as testing the clinical innovations of exercise training to improve the long-term prognosis of osteoporosis in this vulnerable population.

Functional heterogeneity and outcomes in community-dwelling women with osteoporosis, with and without a history of falls

Falls leading to osteoporotic fracture is a substantial issue clinically. By inference from the literature, women with osteoporosis who are classified as having a history of falls may not represent a distinct homogeneous population. However, studies exploring the potential heterogeneity within fallers in women with osteoporosis are scarce. The objective of this study was to better understand the physical function characteristics of women with osteoporosis, with and without a previous history of falls, by further stratifying them based on their single-leg stance (SLS) performance. Eighty-seven consecutive, community-dwelling women with osteoporosis were recruited from the Endocrinology Clinic at Singapore General Hospital. Laboratory-based and clinic-based standing balance tests, a lower limb strength test, and the 6-min walk test (6MWT) were measured. Fallers and non-fallers did not differ in standing balance, lower limb strength nor the 6MWT (P's>0.08). SLS performance was an independent predictor of the various functional measures, after adjusting for age and body mass index. Specifically, an increase in SLS time was associated with lower standing center-of-pressure velocities, greater lower limb strength, and greater 6-min walking distance. When the two groups were stratified based on their recent history of falls and clinic-based standing balance performance (SLS time), fallers with good SLS time (>30 s) showed better functional outcomes than did non-fallers with poor SLS time (≤30 s) (P's<0.08) and comparable functional outcomes with non-fallers with good SLS time (P's>0.11). The results indicate an important heterogeneity within fallers and non-fallers with osteoporosis and they argue for a individualized approach to rehabilitation.

Correlation of postural balance and knee muscle strength in the sit-to-stand test among women with and without postmenopausal osteoporosis

The task of standing up from a chair forms a part of daily life for all independent individuals. However, this task becomes more difficult with advancing age. Women with postmenopausal osteoporosis presented diminished knee extensor and flexor muscle strength. There was a weak correlation between knee muscle strength (greater with extensor strength) and postural balance during the act of standing up.

INTRODUCTION

This study aims to evaluate postural balance during the transition from sitting to standing and its relationship with knee extensor and flexor strength among women with and without postmenopausal osteoporosis.

METHODS

Assessments were made on 126 women (aged 55-65 years), divided into osteoporosis and control groups according to lumbar bone density. Their balance during the task of standing up from a chair was evaluated using the Balance Master® device. Knee muscle strength was evaluated using an isokinetic dynamometer (Biodex®), in concentric/concentric mode, at a velocity of 60°/s. Spearman's correlation between the variables of muscle strength and postural balance was evaluated. Subsequently, to evaluate the association of each balance variable with the group and with muscle strength, multiple linear regression models were fitted. The significance level was set at 0.05.

RESULTS

There was a difference in knee muscle strength between the groups (P < 0.05). However, independent of the muscle strength values, there were no differences in relation to weight transfer times (P = 0.556) or center of gravity sway velocity (P = 0.952). Transfer time diminished with increasing extensor strength (P = 0.025). The center of gravity sway velocity tended to increase with increasing extensor strength (P = 0.013) and was the same in the two groups (P = 0.264).

CONCLUSION

Women with postmenopausal osteoporosis presented diminished knee extensor and flexor muscle strength. There was a weak correlation between knee muscle strength (greater with extensor strength) and postural balance during the act of standing up.

Evaluation of the association between osteoporosis and postural balance in postmenopausal women

The incidence of osteoporosis has been increasing, as have fractures resulting from falls. Postural balance was evaluated in postmenopausal women with and without lumbar osteoporosis. One hundred and twenty-six postmenopausal women aged 55-65 years were evaluated and separated into two groups according to the bone mineral density values of their lumbar spine: the osteoporosis group and the control group, paired by age (P = 0.219) and physical activity (P = 0.611). There was no difference between the groups (P = 0.139) regarding falls reported in the previous 12 months. Functional mobility was evaluated through the Timed Up and Go Test. Postural balance was evaluated using a portable force platform in standard standing position, with eyes open and closed, for 60s. Muscle strength was evaluated through an isokinetic dynamometer. This study shows that there is no difference in knee muscle strength and functional mobility (P = 0.121), postural balance with eyes open [mediolateral displacement (P = 0.286) and mean velocity of the center of pressure (COP) (P = 0.173)] and with eyes closed [mediolateral displacement (P = 0.163), and the mean velocity of displacement of the COP (P = 0.09)] in both groups. Subjects reporting falls had greater mediolateral displacement (P = 0.028) in both groups. Postmenopausal women aged between 55 and 65 years do not present changes in postural balance irrespective of lumbar osteoporosis. Greater COP mediolateral displacement is related to the occurrence of falls in postmenopausal women in the previous year.

Equilíbrio, controle postural e força muscular em idosas osteoporóticas com e sem quedas

Um dos maiores problemas de saúde pública na população idosa são as quedas, agravando-se quando relacionadas à presença de osteoporose. Dentre os vários fatores de risco, destacam-se a diminuição do equilíbrio, controle postural e força muscular. O objetivo deste trabalho foi comparar o equilíbrio, o controle postural e a força muscular em idosas osteoporóticas com e sem quedas referidas no último ano. Foram avaliadas 45 mulheres entre 65 e 85 anos, divididas em dois grupos com base no relato de quedas nos 12 meses anteriores à avaliação: grupo com quedas (GCQ; n=21) e grupo sem quedas (GSQ; n=24). O equilíbrio foi avaliado por meio da escala de equilíbrio de Berg; o controle postural pelo teste clínico modificado de interação sensorial no equilíbrio (mCTSIB), realizado no equipamento Balance Master®; e a força muscular dos flexores e extensores de joelho e dorsiflexores de tornozelo, com dinamômetro EMG System do Brasil®. Foi considerado nível de significância α=0,05. Houve diferença significativa no equilíbrio (p<0,01) e na velocidade de oscilação do Centro de Pressão (CP) durante o teste mCTSIB nas condições olhos fechados superfície estável (p=0,05) e olhos abertos superfície instável (p<0,01), com valores maiores para o GCQ. Os grupos foram semelhantes entre si em relação à força muscular (p>0,05). Nossos resultados indicam que idosas osteoporóticas com histórico de quedas nos últimos 12 meses possuem pior equilíbrio e controle postural em relação às osteoporóticas sem quedas referidas.

Altered postural control in persons with cognitive impairment during visual feedback tasks

We compared postural stability with eyes open (EO) and with visual feedback (VFB) in 15 elderly subjects with cognitive impairment (SwCI) and 17 controls. Postural stability was evaluated using the center-of-pressure (COP) mean radius and velocity, while postural strategies by the frequency and damping of the difference between the COP and the center-of-mass (COM) signals. Performance in the VFB trials was measured by the ratio of time spent by the COP inside the target on the screen to the total trial duration. With EO, both groups demonstrated similar postural stability and strategies. The time spent inside the target during VFB was significantly higher in controls than in SwCI. The VFB did not affect the mean radius in either group, nor velocity and frequency in SwCI, however it increased the mean velocity and frequency in controls. Besides, the VFB increased damping significantly more in the SwCI than in controls. These findings indicate that controls adequately responded to the demands of VFB and used efficient strategy of postural control. In contrast, the SwCI seemed to have lost the natural capability to use augmented feedback demonstrating impaired sway control and deficit of sensory integration. All these symptoms of posture control disorders could be objectively identified by the COP mean velocity and the COP-COM frequency and damping. Increased damping in controls during VFB task may account for early signs of cognitive impairment that cannot be captured by standard tests.

Fall prevention and vitamin D in the elderly: an overview of the key role of the non-bone effects

Preventing falls and fall-related fractures in the elderly is an objective yet to be reached. There is increasing evidence that a supplementation of vitamin D and/or of calcium may reduce the fall and fracture rates. A vitamin D-calcium supplement appears to have a high potential due to its simple application and its low cost. However, published studies have shown conflicting results as some studies failed to show any effect, while others reported a significant decrease of falls and fractures. Through a 15-year literature overview, and after a brief reminder on mechanism of falls in older adults, we reported evidences for a vitamin D action on postural adaptations - i.e., muscles and central nervous system - which may explain the decreased fall and bone fracture rates and we underlined the reasons for differences and controversies between published data. Vitamin D supplementation should thus be integrated into primary and secondary fall prevention strategies in older adults.

Postural control among elderly women with and without osteoporosis: is there a difference?

CONTEXT AND OBJECTIVE

Little is known about postural control among elderly individuals with osteoporosis and its relationship with falls. It has been suggested that elderly women with kyphosis and osteoporosis are at greater risk of falling. The aim of this study was to evaluate posture and postural control among elderly women with and without osteoporosis.

DESIGN AND SETTING

Cross-sectional study conducted at the Physical Therapy and Electromyography Laboratory, School of Medicine, Universidade de São Paulo (USP).

METHODS

Sixty-six elderly women were selected from the bone metabolism disorders clinic, Division of Rheumatology, USP, and were divided into two groups: osteoporosis and controls, according to their bone mineral density (BMD). Postural control was assessed using the Limits of Stability (LOS) test and the Modified Clinical Test of Sensory Interaction and Balance (CTSIBm) and posture, using photometry.

RESULTS

The elderly women with osteoporosis swayed at higher velocity on a stable surface with opened eyes (0.30 versus 0.20 degrees/second; P = 0.038). In both groups, the center of pressure (COP) was at 30% in the LOS, but with different placements: 156° in the osteoporosis group and 178° in the controls (P = 0.045). Osteoporosis patients fell more than controls did (1.0 versus 0.0; P = 0.036).

CONCLUSIONS

The postural control in elderly women with osteoporosis differed from that of the controls, with higher sway velocity and maximum displacement of COP. Despite postural abnormalities such as hyperkyphosis and forward head, the COP position was posteriorized.

Postural control in patients with lumbar disc herniation in the early postoperative period

Chronic spinal disc disease leads to disorders in postural movement coordination. An incorrect asymmetrical movement pattern for the lower limbs loading impairs proprioception and deteriorates postural stability, particularly when the vision is occluded. The standard surgical treatment improves biomechanical conditions in the lumbar spine, reduces pain, yet does it reduce the stability deficit in the upright position? An answer to the latter question would help work out targeted therapy to improve postural stability. We hypothesized that the standard surgical treatment would improve postural stability reflected by decreased sway variability accounting for better use of proprioceptive inputs postoperatively. Thirty-nine patients with lumbar disc herniation participated in the study. Their postural sway was recorded in anterior/posterior and medial/lateral planes with their eyes open or closed (EC) before and after surgery. The variability, range, mean velocity of the recorded time series and the area of the ellipse enclosed by the statokinesiogram were used as measures of postural stability. Preoperatively, EC condition resulted in an increased variability and mean velocity of postural sway, while postoperatively it caused an increase in sway mean velocity and sway area only with no effect on sway variability and range. The comparison of the balance before and after the surgery in the EC condition showed significant decrease in all parameters. In the early postoperative period, the patients recover the ability to control their postural sway in EC within normal limits, however, at the expense of significantly increased frequency of corrective torques. It is probably a transient short-term strategy needed to compensate for the recovery phase when the normal weighting factors for all afferents are being reestablished. We propose that this transient postoperative period may be the best timing of therapeutic intervention targeted at facilitating and reinforcing the acquisition of correct motor patterns.

Body balance evaluation in osteoporotic elderly women

SUMMARY: Osteoporotic Brazilian women balance was evaluated by timed up and go test (TUG) and to the Berg balance scale (BBS). In the BBS, women with and without osteoporosis had normal range scores, even with history of fall. In the TUG test, women with osteoporosis were slower, but in the normal parameter. Results suggest that the references values of these tests are not appropriate for Brazilians. PURPOSES: The purposes of this study were to evaluate balance and functional mobility in women with osteoporosis and without osteoporosis and to verify if the history of falls has association to the TUG and to the BBS, both largely used in the clinical practice. MATERIALS AND METHODS: Forty-five women were divided into three groups: group 1, young women with normal body mineral density (BMD); group 2, elderly with normal BMD; and group 3, elderly with osteoporosis. BBS and TUG were performed, and the history of falls was collected. RESULTS: BBS and TUG showed differences in the scores obtained for young women compared with both elderly with and without osteoporosis. In the TUG test, there were differences between elderly with and without osteoporosis. The fall's history did not present correlations either for TUG or BBS. CONCLUSIONS: Although the results showed that all women were within the normal range for BBS and TUG, the results suggest that the reference values for TUG and BBS are not appropriate for Brazilian population.

Balance training program is highly effective in improving functional status and reducing the risk of falls in elderly women with osteoporosis: a randomized controlled trial

INTRODUCTION

The purpose of this study was to investigate the effect of a 12-month Balance Training Program on balance, mobility and falling frequency in women with osteoporosis.

METHODS

Sixty-six consecutive elderly women were selected from the Osteometabolic Disease Outpatient Clinic and randomized into 2 groups: the 'Intervention', submitted for balance training; and the 'Control', without intervention. Balance, mobility and falling frequency were evaluated before and at the end of the trial, using the Berg Balance Scale (BBS), the Clinical Test Sensory Interaction Balance (CTSIB) and the Timed "Up & Go" Test (TUGT). Intervention used techniques to improve balance consisting of a 1-hour session each week and a home-based exercise program.

RESULTS

Sixty women completed the study and were analyzed. The BBS difference was significant higher in the Intervention group compared to Control (5.5 +/- 5.67 vs -0.5 +/- 4.88 score, p<0.001). Similarly, the number of patients in the Intervention group presented improvement in two conditions of CTSIB compared to Control (eyes closed and unstable surface condition: 13 vs one patient, p < 0.001 and eyes open, visual conflict and unstable surface condition: 12 vs one patient, p<0.001). Additionally, the differences between the TUGT were reduced in the Intervention group compared to Control (-3.65 +/- 3.61 vs 2.27 +/- 7.18 seconds, p< 0.001). Notably, this improvement was paralleled by a reduction in the number of falls/patient in the Intervention group compared to Control (-0.77 +/- 1.76 vs 0.33 +/- 0.96, p=0.018).

CONCLUSION

This longitudinal prospective study demonstrated that an intervention using balance training is effective in improving functional and static balance, mobility and falling frequency in elderly women with osteoporosis.

Adaptive changes in postural strategy selection in chronic low back pain

Chronic low back pain (CLBP) patients achieve postural stability during challenging stance conditions by increasing sway speed. We investigated the mechanisms underlying this behavior, and whether postural strategy selection may be influenced by short-term experience of postural perturbation. Thirteen CLBP patients and thirteen age-matched controls underwent posturography tests. Subjects were asked to stand quietly: (a) with eyes open and eyes closed, and (b) while expecting a series of four backward translations of the support surface. Data from condition (a) was subjected to sway density analysis (SDA). This computes the number of consecutive spaces and respectively time samples during which center of pressure (COP) displacements remained inside a 2.5 mm radius. Three parameters of this analysis were considered: the mean number of peaks (MP), reflecting the time spent by COP in regions of stability, the mean time between peaks (MT) relating to the rate of production of posturographic commands, and the mean spatial distance (MD), reflecting the distance between stable regions. In condition (b) the mean COP positions were analyzed during the time (500 ms) preceding each translation. The MD was significantly increased in the CLBP group as compared to controls (P < 0.01), while the MP and MT did not present any significant difference. The expectation of backward translations initially produced a different COP positioning between the two groups (P < 0.0001) which decreased with repetition of platform translations (controls: PDelta1-4 < 0.002; patients: PDelta1-4 < 0.005). The findings show that the timing and the rate of the balance motor commands is comparable between the two groups. On the other hand, there is greater distance between regions of stability in the patient group. Such modification of motor control patterns might be the consequence of a reweighting of sensory input, possibly due to a deterioration of its reliability. Platform translation findings show that both groups aimed at optimizing their posture selection strategy based on prior testing experience. CLBP patients make use of a different postural motor strategy to maintain quiet stance. This is probably the consequence of an imprecise internal estimate of body sway, due to reduced accuracy in the sensory integration process.