Soleus activity in post-stroke subjects: Movement sequence from standing to sitting

Introduction. The beginning of the movement sequence from standing to sitting requires the modulation of plantar flexors activity, including the soleus muscle (SOL), to allow the forward translation of the tibia in relation to the foot, preserving its antigravity function.

Purpose. To analyze the SOL activity during the initial phase of standing to sitting in stroke subjects.

Methods. Two groups of ten subjects each participated in this study, one composed of healthy subjects and the other with subjects with a history of stroke. Electromyographic activity (EMGa) of SOL was analyzed in the ipsilateral (IPSI) and contralateral (CONTRA) limb to side lesion in stroke subjects, and in one limb in healthy subjects during the initial phase of standing to sitting. A force plate was used to identify the movement sequence phase.

Results. The mean values of SOL EMGa were higher in healthy subjects than the ones obtained in the IPSI and CONTRA limb in stroke subjects. Significant differences were only observed between the IPSI and healthy limb (p?=?0.035).

Conclusion. When compared to the healthy subjects, stroke subjects showed a decreased SOL EMGa in the IPSI limb, which suggests that therapeutic decisions must consider the need to promote a better postural control also in the IPSI limb.     

Quantitative measurement of sympathetic neuropathy in patients with diabetes mellitus

Vasoconstriction occurs in the skin capillary blood flow of the healthy subject when posture changes from supine to standing. Using frequency analysis of the optical photoplethysmograph signal, a statistically significant difference (P<0.01) may be demonstrated between supine and standing positions in the lower frequency band (0.01–0.5 Hz) in the foot of normal subjects. This allowed us to develop a simple index: sympathetic power band change (SPBC). Patients with diabetes mellitus often suffer from degeneration in the sympathetic nervous system. This impairs the normal vasoconstrictor response to standing. We have applied the SPBC ‘blind’ to a group of diabetic patients. Such patients may be divided into three groups according to their SPBC indices: normals with SPBC> 2.6 (group A), intermediates with 2.6 ⩾ SPBC ⩾ 0.26 (group B) and poor with SPBC < 0.26 (group C). All patients with retinopathy were in group C and five out of the six patients with electrophysiologically confirmed peripheral neuropathy were in group C. Frequency analysis of the photoplethysmograph signal has produced an index of sympathetic tone change when subjects move from supine to standing position. The application of this index to patients with diabetes mellitus shows some patients to have sympathetic vascular tone failure.     

Somatosensory impairments in patients with multiple sclerosis: association with dynamic postural control and upper extremity motor function

Abstract

Purpose: We planned this study to bring attention to the somatosensory impairments in patients with multiple sclerosis (PwMS) and to investigate relationship of somatosensory impairments with dynamic postural stability and upper extremity motor function.

Methods: Seven males and 23 females, 30 patients with mean EDSS 2.9 (SD = 1.4), aged between 18 and 65 years (mean = 41.43?±?14.90 years) were included in this clinical study. Light touch sensorial assessment was made with Semmes Weinstein monofilament test and proprioception by distal proprioception test. Hand strength was measured by the Jamar dynamometer, fine motor skill was examined with nine-hole peg test, functional reach test in sitting and standing position was applied. Nottingham Extended Activities of Daily Living Scale (NEADLS) was used to measure everyday activities.

Results: We found a negative and moderate correlation between FRT in standing and light touch of the middle of the heel (right: –0.515), metatarsal bone (right r: 0.453, left r: –0.426), and medial of the foot (right r: –0.462). There was a negative and moderate correlation between NEADLS and light touch of the metatarsal bone (right r: –0.564, left r: –0.472), medial of the foot (right r: –0.531, left r: –0.479), and lateral of the foot (right r: –0.526). We found a positive and moderate correlation between proprioception of the ankle (right r: 0.421 left r: 0.588) and NEADLS.

Conclusions: We found impairment in light touch and proprioception and, associations between sensorial functions and dynamic postural stability in PwMS. Also impaired sensorial functions cause dependent patients in daily living activities. In the assessment of balance and falling risk, independency in daily living activities; foot light touch and proprioception sense should be taken into account, hence it may provide guidance in planning rehabilitation programmes.

Abbreviations: MS: multiple sclerosis; PwMS: patients with multiple sclerosis; VAS: visual analogue scale; FRT: functional reach test; 9-HPT: Nine-hole peg test; EDSS: The Expanded Disability Status Scale; NEADLS: Nottingham Extended Activities of Daily Living Scale     

Validity of hand-to-foot measurement of bioimpedance: standing compared with lying position

Objective: To assess the reliability of the standing measurement of hand‐to‐foot bioimpedance compared with measurements made in the lying position. Research Methods and Procedures: In 205 volunteers 6 to 89 years of age, 111 males and 94 females from six ethnic groups, effects of posture, time, and age on hand‐to‐foot resistance were studied over a range of body size. The effect of time in a position on resistance was also recorded in a small subset (n = 10), and repeat measurements over 3 days at the same time of the day were recorded in another subset (n = 12). Results: Lying impedance was consistently higher than standing, with the relationship (resistance lying/resistance standing) for the children (5 to 14 years) being 1.031, progressing to a ratio of 1.016 in those >60 years. The time spent static in either position did change resistance measurements—a decrease of up to 9 Ω (mean 5 Ω, 1.0%) over 10 minutes of standing and an increase of up to 7 Ω (mean 3 Ω, 0.7%) with lying. Discussion: In the field, measurements of hand‐to‐foot bioimpedance can be made in the standing position, and, with appropriate adjustment, previously validated recumbent equations can be used. Given that errors in the measurement of height and weight also affect the reliability of the derivation of body fat from bioelectrical conductance, the errors that may arise from a more practical standing measurement rather than lying are minimal.     

Using a dry electrode EEG device during balance tasks in healthy young-adult males: Test–retest reliability analysis

Abstract

Background: The analysis of brain activity during balance is an important topic in different fields of science. Given that all measurements involve an error that is caused by different agents, like the instrument, the researcher, or the natural human variability, a test–retest reliability evaluation of the electroencephalographic assessment is a needed starting point. However, there is a lack of information about the reliability of electroencephalographic measurements, especially in a new wireless device with dry electrodes.

Objective: The current study aims to analyze the reliability of electroencephalographic measurements from a wireless device using dry electrodes during two different balance tests.

Method: Seventeen healthy male volunteers performed two different static balance tasks on a Biodex Balance Platform: (a) with two feet on the platform and (b) with one foot on the platform. Electroencephalographic data was recorded using Enobio (Neuroelectrics). The mean power spectrum of the alpha band of the central and frontal channels was calculated. Relative and absolute indices of reliability were also calculated.

Results: In general terms, the intraclass correlation coefficient (ICC) values of all the assessed channels can be classified as excellent (>0.90). The percentage standard error of measurement oscillated from 0.54% to 1.02% and the percentage smallest real difference ranged from 1.50% to 2.82%.

Conclusion: Electroencephalographic assessment through an Enobio device during balance tasks has an excellent reliability. However, its utility was not demonstrated because responsiveness was not assessed.     

The relationship between dynamic balancing ability and posture-related modulation of the soleus H-reflex

Soleus H-reflex reveals down modulation with increased postural difficulty. Role of this posture-related reflex modulation is thought to shift movement control toward higher motor centers in order to facilitate more precise postural control. Present study hypothesized that the ability to modulate H-reflex is related to one’s ability to dynamically balance while in an unstable posture. This study examined the relationship between dynamic balancing ability and soleus H-reflex posture-related modulation. Thirty healthy adults participated. The soleus maximal H-reflex (Hmax), motor response (Mmax), and background EMG activity (bEMG) were obtained during three postural conditions: prone, open-legged standing, and closed-legged standing. Hmax/Mmax ratios were normalized via the corresponding bEMG in order to remove the effects of background muscle activity from the obtained H-reflex. Reflex modulation was calculated as the ratio of the normalized Hmax/Mmax ratios in one postural condition to another posture in a more difficult condition. Dynamic balancing ability was assessed by testing stability while standing on a wobble board. A significant negative correlation was observed between balancing scores and reflex modulation from open-legged standing to closed-legged standing. This suggests that the ability to modulate monosynaptic stretch reflex excitability in response to a changing posture is a significant factor for dynamic balancing.     

Relationship of multiscale entropy to task difficulty and sway velocity in healthy young adults

Abstract

Purpose/background: Multiscale entropy (MSE) is a nonlinear measure of postural control that quantifies how complex the postural sway is by assigning a complexity index to the center of pressure (COP) oscillations. While complexity has been shown to be task dependent, the relationship between sway complexity and level of task challenge is currently unclear. This study tested whether MSE can detect short-term changes in postural control in response to increased standing balance task difficulty in healthy young adults and compared this response to that of a traditional measure of postural steadiness, root mean square of velocity (VRMS).

Methods: COP data from 20?s of quiet stance were analyzed when 30 healthy young adults stood on the following surfaces: on floor and foam with eyes open and closed and on the compliant side of a Both Sides Up (BOSU) ball with eyes open. Complexity index (CompI) was derived from MSE curves.

Results: Repeated measures analysis of variance across standing conditions showed a statistically significant effect of condition (p?<?0.001) in both the anterior–posterior and medio-lateral directions for both CompI and VRMS. In the medio-lateral direction there was a gradual increase in CompI and VRMS with increased standing challenge. In the anterior–posterior direction, VRMS showed a gradual increase whereas CompI showed significant differences between the BOSU and all other conditions. CompI was moderately and significantly correlated with VRMS.

Conclusions: Both nonlinear and traditional measures of postural control were sensitive to the task and increased with increasing difficulty of standing balance tasks in healthy young adults.     

The Relationships between Foot Arch Volumes and Dynamic Plantar Pressure during Midstance of Walking in Preschool Children

Objectives

The purpose of this study was to examine the correlation between the foot arch volume measured from static positions and the plantar pressure distribution during walking.

Methods

A total of 27 children, two to six years of age, were included in this study. Measurements of static foot posture were obtained, including navicular height and foot arch volume in sitting and standing positions. Plantar pressure, force and contact areas under ten different regions of the foot were obtained during walking.

Results

The foot arch index was correlated (r = 0.32) with the pressure difference under the midfoot during the foot flat phase. The navicular heights and foot arch volumes in sitting and standing positions were correlated with the mean forces and pressures under the first (r = −0.296∼−0.355) and second metatarsals (r = −0.335∼−0.504) and midfoot (r = −0.331∼−0.496) during the stance phase of walking. The contact areas under the foot were correlated with the foot arch parameters, except for the area under the midfoot.

Conclusions

The foot arch index measured in a static position could be a functional index to predict the dynamic foot functions when walking. The foot arch is a factor which will influence the pressure distribution under the foot. Children with a lower foot arch demonstrated higher mean pressure and force under the medial forefoot and midfoot, and lower contact areas under the foot, except for the midfoot region. Therefore, children with flatfoot may shift their body weight to a more medial foot position when walking, and could be at a higher risk of soft tissue injury in this area.     

Balance control is impaired in adults with sickle cell anaemia

Abstract

Background: Musculoskeletal involvement and cerebrovascular disease are common in sickle cell anaemia (SCA). These changes are potentially important factors that modify the control of balance in this population.

Objective: To assess balance control in adults with SCA and investigate the associations among balance, posture and muscle function.

Methods: Twenty neurologically intact (i.e. without previous episodes of overt stroke or transient ischaemic attack) adults with SCA and 18 controls were evaluated. All participants underwent static balance measurement through stabilometry, postural evaluation through photogrammetry and assessment of muscle function through handgrip and respiratory muscle strength.

Results: Compared to the controls, the adults with SCA exhibited greater displacement of the centre of mass, particularly in the mediolateral direction. Moreover, the adults with SCA exhibited greater postural deviations for the following variables: angles of the right and left hip, horizontal asymmetry of the scapula in relation to T3, angles of the right and left leg-heel and horizontal alignment of the pelvis. Handgrip strength, respiratory muscle strength and haemoglobin (Hb) levels were significantly correlated with postural balance measurements. Significant correlations between balance and posture were only observed between the variables of balance and the postural parameters that involved the angulations calculated from the vertical alignment of the pelvis, hip and ankle.

Conclusions: Neurologically intact adults with SCA exhibit damage in static balance, particularly in the mediolateral direction. These patients present postural deviations due to changes in the hip and ankle joints. In addition, balance control is related to posture, Hb level and muscle function.     

Effect of tongue position on postural stability during quiet standing in healthy young males

Abstract

Background and aims: Role of the neck and jaw sensory motor system in control of body balance has been established. Tongue is an integral part of jaw sensory motor system and helps in execution of purposeful and precise motor tasks like eating, drinking and speaking. The purpose of this study was to evaluate the possible effects of tongue position on the postural control system.

Materials and method: We compared the mean center of gravity (COG) velocity during quiet standing on an unstable surface with eyes closed during two test conditions: (i) with habitual jaw resting position and (ii) with instructed tongue positioned against the upper incisors. One hundred and sixteen normal healthy male subjects (average age 31.56?±?8.51 years and height 170.86?±?7.26?cm) participated in the study. Their COG velocity (deg/s) was measured using the NeuroCom® Balance Master version 8.5.0 (Clackamas, OR, USA).

Results and conclusions: The results show that COG velocity decreased significantly while tongue was positioned against upper incisors in comparison to the habitual jaw resting position. Our findings suggest that the tongue positioning can modulate postural control mechanisms. Tongue positioning against the upper incisors can enhance the postural stability during upright standing on an unstable surface and in the absence of vision in healthy young adults. Our findings can be of value for evaluation and rehabilitation protocols for postural control dysfunction.     

Human upright posture control in a virtual visual environment

The sagittal and frontal components of the stabilogram were monitored in 14 healthy subjects standing on a rigid or pliant support under three different conditions of visual control: with the eyes opened (EO), with the eyes closed (EC), or in a virtual visual environment (VVE). Under the VVE conditions, the subjects looked at a three-dimensional image of elements of a room (a 3-D artificial room) that was generated by a computer and locked to the fluctuations of the body center of gravity (CG) so that the visual connection between body sway and shifts of the visual environment typical of normal visual conditions was reproduced. Frequency filtration of the fluctuations of the foot’s center of pressure (FCP) was used to isolate the movements of the vertical projection of the CG and determine the difference between these two variables. The changes in the variables (CG and FCP-CG) were estimated using spectral analysis followed by the calculation of the root mean square (RMS) amplitudes of their spectral fluctuations. In subjects standing on a rigid support, the RMS amplitudes of the spectra of both variables were the highest under the VVE and EC conditions and the lowest under the EO conditions. In subjects standing on a pliant support, body sway was considerably enhanced, which was accompanied by a different pattern of visual influences. The RMS values were the highest under the EC conditions and were lower by a factor of 2–2.5 under the EO and VVE conditions. Thus, it has been demonstrated that the cerebral structures controlling posture ignore the afferent input from the eyes under VVE conditions, if the subject is standing on a rigid support and the CG fluctuations are relatively small; however, this afferentation is efficiently used for maintaining the posture on a pliable support, when the body sway is substantially enhanced.     

Effect of dentures wearing on motor reaction time and balance function in elderly people

OBJECTIVE: To investigate the influence of dentures wearing on the parameters of physical fitness, particularly on agility and balance function in elderly people. DESIGN: A case control study.Setting: Motohachiohjimachi, Hachiohji, Tokyo, Japan. METHODS: Motor reaction time was measured in the presence and absence of dentures in the subjects who were 1) in a sitting position and lifted the lower limbs as fast as possible in response to a stimulus (Sitting Group) and those who were 2) in a standing position and jumped upright as fast as possible in response to a light stimulus (Jumping Group). The effects of dentures wearing on balance function were investigated by comparing the measured values of static and dynamic body sway. RESULTS AND CONCLUSIONS: Light-reaction time was not significantly influenced by dentures wearing in Sitting Group performing a light body movement that required little muscular force.In a relatively heavy body movement that required agility (i.e., jumping from the standing position), the reactivity changed depending on the muscular force; which might result in the difference of the reactivity due to dentures wearing (i.e., t-test showed a significant difference in the light-reaction time under clenching posture between with and without wearing dentures (p < 0.01)).No significant difference was observed in body sway under clenching posture between with and without wearing dentures.Therefore, we assumed that reaction speed varied depending upon dentures wearing.     

10周核心力量练习对男性中老年人平衡能力的影响

目的：探讨核心力量练习对中老年男性平衡能力的影响,为运动锻炼改善老年人平衡能力和降低跌倒风险提供依据。方法：选取16名50~60岁男性中老年人,随机分为试验组（核心力量练习）和对照组,每组8人。利用悬吊绳和瑜伽垫进行动、静态支撑与推拉练习以及徒手下肢力量等间歇性组合核心力量训练,共练习10周,每周4~5次,每次50~60 min。对照组保持原有生活习惯。锻炼前后测定受试者静态平衡和动态平衡等指标。结果：①锻炼后试验组闭眼单脚站立时间和动态平衡得分较锻炼前显著升高分别为（9.00±2.27） s、（10.63±1.69） s,P<0.01;（77.38±10.94）、（89.50±5.53）,P<0.01。②锻炼后试验组星形伸展平衡测试（SEBT）,右腿支撑时左腿在8个方向、左腿支撑时右腿在6个方向的SEBT值均较锻炼前显著增加（P<0.01）。结论：10周核心力量练习显著提高男性中老年人的动、静态平衡能力。     

Implication of obesity on motion,posture and internal stress of the foot: an experimental and finite element analysis

Obesity causes increased loading on the foot which can damage the soft tissue and bone ultimately leading to foot problems. Experimental and computational methods were used to analyse the chain of biomechanical changes in the lower limb due to obesity. The experimental study shows some changes in foot posture and gait where obese subjects were more likely to have pronated feet, smaller joint angles in the sagittal and frontal planes, smaller cadence, and smaller stride length. Anatomically correct finite element models generated on obese subjects showed increased and altered internal and plantar stress. Altered foot posture was identified as a key indicator of increased internal stress indicating the importance of foot posture correction.     

Effects of excessive body weight on postural control

Research that evaluated both static and dynamic stability was performed, to clarify the impact of excessive body weight on postural control. The spontaneous center of foot pressure (CP) motion during quiet stance and a range of forward voluntary CP displacements were studied in 100 obese, and 33 lean women. Characteristics of postural sway were acquired while the subjects were standing quiet on a force plate with eyes open (EO) and with eyes closed (EC). Their anterior range of CP voluntary displacements was assessed upon a range of maximal whole body leanings which were directed forward. A substantial reduction of postural sway was observed in all patients which had increased body weight. Main postural sway parameters i.e., the total path length as well as its directional components were negatively correlated with the body mass and body mass index (BMI). The range of a whole body voluntary forward leaning, did not exhibit any significant change in patients with an obesity grade of I and II. Such a deficit was, however, found in subjects with a body mass index above 40. In conclusion, the increased body weight imposed new biomechanical constraints, that resulted in functional adaptation of the control of the erect posture. This functional adaptation was characterized by a reduced postural sway associated with a substantial reduction of the dynamic stability range in subjects with BMI>40.     

Gender‐specific Effect of Obesity on Balance

Obesity modifies the body geometry by adding mass to different regions and it influences the biomechanics of activities of daily living. Weight influences postural stability, but there is no consensus as to whether the different fat distribution in males and females produces gender‐related effects on balance. The aim of this study was to investigate the effect of body weight increases on postural performance in males and females. A total of 22 obese females (BMI: 41.1 ± 4.1 kg/m²) and 22 obese males (BMI: 40.2 ± 5 kg/m²) were analyzed during a static posture trial on a force platform in standardized conditions. Twenty healthy subjects (10 females, 10 males) constituted the control group. We computed the following parameters related to the center of pressure (CoP): velocity and displacements along the antero‐posterior (AP) and medio‐lateral axis (ML). We found several statistically significant differences between healthy and obese men, in particular regarding the AP and ML CoP parameters, which were correlated to body weight (r = 0.36–0.58). The comparison between healthy and obese females pointed out statistically significant differences in AP parameters and no significant differences in ML displacements. Body weight was found to correlate with AP parameters (r = 0.36–0.74), but not with ML displacements. The increased body mass seems to produce AP instability in both genders and ML destabilization only in males. Rehabilitation programs should take these findings into account by adopting specific interventions to improve ML control in obese males, and through weight loss and strengthening of ankle flexors/extensors in both genders.     

Experimental verification of a computational technique for determining ground reactions in human bipedal stance

We have developed a three-dimensional (3D) biomechanical model of human standing that enables us to study the mechanisms of posture and balance simultaneously in various directions in space. Since the two feet are on the ground, the system defines a kinematically closed-chain which has redundancy problems that cannot be resolved using the laws of mechanics alone. We have developed a computational (optimization) technique that avoids the problems with the closed-chain formulation thus giving users of such models the ability to make predictions of joint moments, and potentially, muscle activations using more sophisticated musculoskeletal models. This paper describes the experimental verification of the computational technique that is used to estimate the ground reaction vector acting on an unconstrained foot while the other foot is attached to the ground, thus allowing human bipedal standing to be analyzed as an open-chain system. The computational approach was verified in terms of its ability to predict lower extremity joint moments derived from inverse dynamic simulations performed on data acquired from four able-bodied volunteers standing in various postures on force platforms. Sensitivity analyses performed with model simulations indicated which ground reaction force (GRF) and center of pressure (COP) components were most critical for providing better estimates of the joint moments. Overall, the joint moments predicted by the optimization approach are strongly correlated with the joint moments computed using the experimentally measured GRF and COP (0.78 < or = r(2) < or = 0.99,median,0.96) with a best-fit that was not statistically different from a straight line with unity slope (experimental=computational results) for postures of the four subjects examined. These results indicate that this model-based technique can be relied upon to predict reasonable and consistent estimates of the joint moments using the predicted GRF and COP for most standing postures.     

Serum levels of oncostatin M (a gp 130 cytokine): an inflammatory biomarker in periodontal disease

Objective: Periodontitis is considered to be a risk factor for systemic diseases such as atherosclerosis, diabetes, etc., and cytokines play a key role. The present study was carried out to measure the level of serum oncostatin M (OSM) in patients with chronic periodontitis, and to evaluate the effect of non-surgical periodontal therapy on the serum OSM concentration.

Materials and methods: Sixty subjects were divided into three groups (each group n?=?20) based on the gingival index (GI), probing pocket depth (PPD) and clinical attachment level (CAL): group I healthy; group II gingivitis; and group III chronic periodontitis. Group III patients were followed for 8 weeks after non-surgical periodontal therapy as the after-treatment group (group IV). Estimation of serum OSM was done using an enzyme-linked immunosorbent assay.

Results: The mean OSM concentrations in serum were highest in the chronic periodontitis group (mean 68.05 pg ml^?1) and decreased following treatment (39.65 pg ml^?1) while OSM was undetectable in healthy subjects or in patients with gingivitis.

Conclusion: Increased serum OSM concentration in patients with chronic periodontitis and its positive correlation with PPD and CAL, suggest its role as an inflammatory biomarker in periodontal disease and it may exaggerate other systemic conditions such as atherosclerosis and rheumatoid arthritis.     

Immediate effect of individual bars of insoles and their combination on gait parameters in asymptomatic healthy adults

Abstract

Objective: The way how individual bars of sensorimotor insoles influence the gait kinematics is not fully understood yet. Therefore, this study aimed to explore the effect of three sensorimotor orthotic conditions (the medial calcaneal and retrocapital lateral bars and their combination) on the gait parameters in healthy adults during the stance phase of gait cycle.

Materials and methods: Twenty-six young adults performed 20 gait cycles in each condition using their self-selected cadence and provided standardised shoes with the base-sole and the three types of orthotics. A three-dimensional motion analysis system (8 cameras; 200?Hz) was used and a six-degrees of freedom model was applied. The cadence, the stride length, the first peaks of foot external rotation, eversion and dorsal flexion as well as the first peak of hip adduction were analysed.

Results: Significant differences (p?<?0.05) were found for all parameters between the orthotic conditions, except the cadence. Significant difference in the first peak of hip adduction (p?=?0.008) was found between the dominant and non-dominant leg. There were no significant interactions between the factors of condition and leg dominance (p?>?0.05).

Conclusions: There seems to be overall tendencies in immediate changes in ankle joint kinematics caused by all three sensorimotor orthotic conditions and besides the mechanical principles, also ‘proprioceptive mechanism’ seems to play a role. However, maximum observed average angular change was 2° and some variability in reactions to each orthotic condition exists among the individuals. Therefore, clinical relevance of such changes remains unclear and careful analysis of expected outcomes should be the common part of every orthotic intervention.