Time dependent structure of postural sway in individuals with multiple sclerosis

Non-linear analyses, which examine the time dependent structure of physiological output have been found to be able to detect subtle differences in postural control between pathological groups and healthy controls while traditional linear parameters do not. This investigation examines whether a specific non-linear metric, approximate entropy, may provide a novel biomarker for balance impairment in individuals with multiple sclerosis (MS) who have normal sway. This analysis included a sample of 30 individuals with MS with normal postural sway and 36 controls. Participants stood on a force platform for two trials of 30 s with eyes open. Postural control was indexed by sway area, mean velocity along the antero-posterior (AP) and mediolateral (ML) axis. The time dependent structure of the COP along the AP and ML axes was indexed with approximate entropy (ApEn_AP; ApEn_ML). T-tests and Mann–Whitney U tests were utilized to analyze differences between groups. Per design there were no differences in sway area between the MS and control groups. Additionally, there were no differences in sway velocity. The MS group had lower ApEn_ML values compared to the control group (U = 376, p = .026). The results indicate that individuals with MS who have normal sway area had greater time dependent structure in ML sway. This investigation highlights the utility of non-linear analyses when assessing balance impairment in MS samples that present with minimal sway area.     

Balance impairment in kidney transplant recipients without concurrent peripheral neuropathy

Kidney transplant recipients (KTRs) present with compromised functional capacity, low levels of physical activity, muscle atrophy, and peripheral nerve dysfunction that may result in high postural instability. This study aimed to compare the static balance control of 19 KTRs with 19 healthy adults (HA). All participants completed the Romberg test on a stabilometric platform with eyes open (EO), eyes closed (EC) and during a dual task (DT) condition. Centre of pressure (COP) measures (COP velocity (COPv) and sway area (SA)), as well as position-based outcomes such as anterior-posterior (AP) and medio-lateral (ML) ranges of COP displacements were recorded. Independent ANCOVA revealed an overall lower performance of KTRs compared to HA (p < 0.05) with the EC condition exhibiting the worst relative performance for KTRs, suggesting a poorer capacity of relying on proprioceptive information when maintaining the upright posture. The addition of a cognitive task did not further worsen balance performance in KTRs. As impaired postural control is one of the main predictors of falls in elderly subjects, these data might also indicate that this constitutes an equivalent risk factor for falling in middle-aged KTRs.     

Balance dysfunction in hereditary and spontaneous spastic paraparesis

ObjectiveTo determine how postural sway is affected in people with spastic paraparesis (pwSP) and the impact of different impairments.MethodsIn 20 pwSP and 18 matched healthy controls standing postural sway was measured with eyes open and closed. Vibration threshold, isometric ankle and hip muscle strength and ankle stiffness with the participant at rest or preactivating the muscle was measured.ResultsAntero-posterior (AP) and medio-lateral (ML) sway was higher in pwSP. Muscle strength was reduced and ankle stiffness increased in pwSP. Increased vibratory threshold was seen in 35% of participants. Higher total ankle stiffness (R² = 0.44) was associated with lower AP sway with eyes open whilst hip abductor weakness was associated with increased ML sway with eyes open (R² = 0.36) or closed (R² = 0.47) or AP sway with the eyes closed (R² = 0.48).ConclusionsThe degree of postural sway was related to muscle paresis of the hip abductors particularly in the ML direction and under conditions of reduced sensory input. People with higher total ankle stiffness have less AP sway suggesting that this may help to stabilise the body.     

Quantitative trunk sway and prediction of incident falls in older adults

Poor balance and balance impairments are major predictors of falls. The purpose of the current study was to determine the clinical validity of baseline quantitative static trunk sway measurements in predicting incident falls in a cohort of 287 community-dwelling non-demented older Americans (mean age 76.14 ± 6.82 years; 54% female). Trunk sway was measured using the SwayStar™ device, and quantified as angular displacement in degrees in anterior-posterior (pitch) and medio-lateral (roll) planes. Over a one-year follow-up period, 66 elders (23%) reported incident falls. Anterior-posterior angular displacement was a strong predictor of incident falls in older adults in Cox proportional hazards models (hazard ratio adjusted for age, gender, education, RBANS total score, medical comorbidities, geriatric depression scale score, sensory impairments, gait speed, and history of fall in the past 1 year ((aHR) = 1.59; p = 0.033) whereas, angular displacement in the medio-lateral plane was not predictive of falls (aHR = 1.35; p = 0.276). Our results reveal the significance of quantitative trunk sway, specifically anterior-posterior angular displacement, in predicting incident falls in older adults.     

Vibrotactile tilt feedback improves dynamic gait index: A fall risk indicator in older adults

The purpose of this study was to determine the effectiveness of vibrotactile feedback of body tilt in improving dynamic gait index (DGI) a fall risk indicator in community dwelling older adults. Twelve healthy elderly subjects (three males and nine females, age 79.7 ± 5.4 yrs) were tested in an institutional balance rehabilitation laboratory to investigate changes between the feedback off and on conditions. Subjects were acutely exposed to a vibrotactile display that indicated the magnitude and direction of their body tilt from the vertical. DGI and mediolateral (ML) sway were determined during locomotion with, and without, vibrotactile tilt feedback (VTTF). All subjects were at risk for falls based on their initial DGI Score (range: 15–19, mean 17.4 ± 1.56), which was taken with the vibratory stimulus turned off. Subjects learned to use the trunk tilt information from the vibrotactile feedback vest through 20–30 min of gait and balance training consisting of activities that challenged their balance. Subjects were then retested on the DGI. Statistically significant changes were demonstrated for the DGI total score while using the vibrotactile tilt feedback. DGI total scores improved from 17.1 ± 0.4 to 20.8 ± 0.3 (p < 0.05). We conclude that vibrotactile tilt feedback improves both control of mediolateral sway during gait and dynamic gait index. Both are fall risk indicators for this population.     

Effect of hearing aids on static balance function in elderly with hearing loss

While a few studies have investigated the relationship between hearing acuity and postural control, little is known about the effect of hearing aids on postural stability in elderly with hearing loss. The aim was to compare static balance function between elderly with hearing loss who used hearing aids and those who did not use. The subjects asked to stand with (A) open eyes on rigid surface (force platform), (B) closed eyes on rigid surface, (C) open eyes on a foam pad, and (D) closed eyes on a foam pad. Subjects in the aided group (n = 22) were tested with their hearing aids turned on and hearing aids turned off in each experimental condition. Subjects in the unaided group (n = 25) were tested under the same experimental conditions as the aided group. Indicators for postural stability were center of pressure (COP) parameters including; mean velocity, standard deviation (SD) velocity in anteroposterior (AP) and mediolateral (ML) directions, and sway area (95% confidence ellipse). The results showed that within open eyes–foam surface condition, there was greater SD velocity in the off-aided than the on-aided and the unaided than the on-aided (p < 0.0001 for SD velocity in AP and ML). Also, no significant differences were found between the off-aided and unaided group (p = 0.56 and p = 0.77 for SD velocity in AP and ML, respectively). Hearing aids improve static balance function by reducing the SD velocity. Clinical implications may include improving hearing inputs in order to increase postural stability in older adults with hearing loss.     

Multiscale entropy identifies differences in complexity in postural control in women with multiple sclerosis

Loss of postural center-of-pressure complexity (COP complexity) has been associated with reduced adaptability that accompanies disease and aging. The aim of this study was to identify if COP complexity is reduced: (1) in those with Multiple Sclerosis (MS) compared to controls; (2) when vision is limited compared to remaining intact; and (3) during more demanding postural conditions compared to quiet standing. Additionally, we explored the relationship between the COP complexity and disease severity, fatigue, cutaneous sensation and central motor drive. Twelve women with MS and 12 age-matched controls were tested under quiet standing and postural maximal lean conditions with normal and limited vision. The key dependent variable was the complexity index (C_I) of the center of pressure. We observed a lower C_I in the MS group compared to controls in both anterior-posterior (AP) and medio-lateral (ML) directions (p's < 0.002), during the performance of maximal self-regulated leans (AP: p < 0.001; ML: p = 0.018), and under limited vision (AP: p = 0.001; ML: p = 0.006). No group-by-vision interaction (p > 0.05) was observed, indicating that limiting vision did not impact COP complexity differently in the two groups. Decreased cutaneous sensitivity was associated with lower C_I values in the AP direction among those with MS (r² = 0.57); all other measures did not exhibit significant relationships. The findings reported here suggest that (1) MS is associated with diminished COP complexity under both normal and challenging postures, and (2) complexity is strongly correlated with cutaneous sensitivity, suggesting the unique contribution of impaired somatosensation on postural control deficits in persons with MS.     

Postural sway following cryotherapy in healthy adults

In light of the wide use of cryotherapy and its potential negative effects on postural stability, little is known about how postural sway is affected, particularly when the whole lower limb is immersed. The purpose of this study was to analyze the influence of cryotherapy on postural sway in healthy males. Twenty-six subjects were randomly assigned into two intervention groups: control (tepid water at ∼26 °C) or ice (cold water at ∼11 °C). Postural sway was measured through the center of pressure (COP) position while they stood on a force plate during bipedal (70 s) and unipedal (40 s) conditions before and after the subjects were immersed in a water tub up to the umbilical level for 20 min. COP standard deviation (SD) and COP velocity were analyzed in the anterior–posterior (AP) and medial–lateral (ML) directions. Statistical analysis showed that in the bipedal condition cryotherapy increased the COP SD and COP velocity in the ML direction. During the unipedal condition, a higher COP velocity in the AP and ML directions was also reported. Our findings indicate that cryotherapy by immersing the whole lower limb should be used with caution before engaging in challenging postural control activities.     

Quantifying stair gait stability in young and older adults,with modifications to insole hardness

Stair gait falls are prevalent in older adults aged 65 years and older. Extrinsic variables such as changes to insole hardness are important factors that can compromise the balance control system and increase the incidence of falls, especially since age-related decline in the cutaneous sensation is common. Balance measurements such as the minimum center of mass/base of support (COM–BOS, termed ‘stability margin') and COM–BOS medial/lateral range provide information about stability during stair gait. This study was conducted to investigate stair gait stability of young and older adults, with modifications to insole hardness. Twenty healthy adults (10 young adults, 10 older adults) were recruited (mean age = 23.1, SD 2.1; mean age = 73.2, SD 5.5) and instructed to descend a 4 step staircase, for a total of 40 trials. All participants wore similar canvas shoes of varying sizes, and corresponding insole hardnesses (barefoot, soft, medium, hard). Kinematic equipment utilized 12 infrared markers anteriorly placed on the individual to record COM motion and BOS location. The findings from the study demonstrated that older adults were less stable during stair descent. Consequently, insole conditions revealed that the barefoot condition may increase the likelihood of falls, as opposed to the other insole hardnesses (soft, medium and hard). These results suggest that older adults while barefoot are putting themselves at a great risk of falling during stair descent. Since age-related changes are inevitable and the preferred footwear of choice inside the home is bare feet, this is a crucial issue that should be addressed.     

Root mean square of lower trunk acceleration during walking in patients with unilateral total hip replacement

Although several studies have described abnormal trunk motion before and after total hip arthroplasty (THA) surgery, few studies have examined trunk motion using accelerometry. The aim of this study was to determine whether abnormal trunk motion persisted after THA using accelerometry.A total of 24 female patients (61.0 ± 6.9 years) and 20 healthy female subjects (59.9 ± 6.8 years) participated in this study. Patients were assessed at 1 month prior to surgery and 12 months after surgery. Trunk acceleration during gait was measured using a triaxial accelerometer attached to the L3 spinous process. We calculated the root mean square (RMS) and RMS ratio (RMSR) in the vertical (VT), medio-lateral (ML), and anterior–posterior (AP) directions.Results revealed that the RMS in the VT and AP directions postoperatively was greater than that preoperatively, whereas there was no difference in the RMS in the ML direction. In addition, the preoperative RMSR in the ML direction was significantly greater compared with that of healthy individuals and the postoperative RMSR. There was no difference in the RMSR in the ML direction between healthy individuals and postoperatively.These findings suggested that the trunk motion in the frontal plane prior to surgery had improved and was comparable to that of healthy individuals following THA.     

The effect of visual field manipulations on standing balance control in people with multiple sclerosis

BackgroundMultiple sclerosis (MS) is associated with an increased risk of falls, degeneration of sensory organization, and possible increased reliance on vision for balance control.Research questionThe aim of this study was to assess differences in standing postural control between people with MS and age and sex matched controls during medial-lateral (ML) oscillations of the visual field, with and without blinders to the lower periphery.MethodsTen persons with MS (mean age 54.0 ± 5.3 years) and ten age and sex matched controls (mean age: 56.3 ± 6.0 years) participated in this study. Balance control was assessed while participants stood in a Christie Cave system while wearing stereoscopic glasses that projected an immersive forest scene. Visual conditions consisted of 2 m ML visual oscillations of the scene at five frequencies (0.0, 0.3, 0.6, 0.7 and 0.8 Hz) with and without blinders to block the lower periphery.Results and significanceThe results demonstrated that, in comparison to controls, participants with MS had a significantly larger center of pressure sway in both the ML and AP direction to ML visual oscillations. Additionally, participants with MS and controls both increased center of pressure frequency content to the visual oscillation frequency, while participants with MS also increased relative power at the visual oscillation frequency in the AP direction. Blinders of lower periphery reduced the percent power at the visual oscillation frequency in both groups and reduced overall sway in participants with MS during visual oscillations. Overall, results indicate that postural balance is sensitive to visual feedback in people with MS. The elicited AP sway to ML visual oscillation could reflect errors in visual processing for the control of balance, and decreased sway in response to blocking vision of the lower peripheral field could indicate an increased reliance on visual cues to maintain balance.     

Impaired postural control in children with developmental coordination disorder is related to less efficient central as well as peripheral control

BackgroundDevelopmental coordination disorder (DCD) is a neurodevelopmental impairment that affects approximately 6% of children in primary school age. Children with DCD are characterized by impaired postural control. It has yet to be determined what effect peripheral and central neuromuscular control has on their balance control.ObjectiveThe aim of this study was to investigate the underlying mechanisms to impaired postural control in children with DCD using the rambling-trembling decomposition of the center of pressure (CoP).MethodNine children with DCD (9.0 ± 0.5 years, 7 boys, 2 girls) and 10 age- and gender-matched typically developing children (TD) with normal motor proficiency (9.1 ± 0.4 years, 7 boys and 3 girls) performed 3 × 30 s bipedal standing on a force plate in six sensory conditions following the sensory organization procedure. Sway length was measured and rambling-trembling decomposition of CoP was calculated in medio-lateral (ML) and anterior-posterior (AP) direction.ResultsBoth rambling and trembling were larger for the children with DCD in AP (p = 0.031; p = 0.050) and ML direction (p = 0.025; p = 0.007), respectively.ML rambling trajectories did not differ in any conditions with fixed support surface. In ML direction children with DCD had a lower relative contribution of rambling to total sway (p = 0.013).ConclusionThis study showed that impaired postural control in children with DCD is associated with less efficient supraspinal control represented by increased rambling, but also by reduced spinal feedback control or peripheral control manifested as increased trembling.     

Visual contribution to postural stability: Interaction between target fixation or tracking and static or dynamic large-field stimulus

Stationary visual information has a stabilizing effect on posture, whereas moving visual information is destabilizing. We compared the influence of a stationary or moving fixation point to the influence of stationary or moving large-field stimulation, as well as the interaction between a fixation point and a large-field stimulus. We recorded body sway in 20 healthy subjects who were fixating a stationary or oscillating dot (vertical or horizontal motion, 1/3 Hz, ±12° amplitude, distance 96 cm). In addition, a large-field random dot pattern (extension: ～80 × 70°) was stationary, moving or absent. Visual fixation of a stationary dot in darkness did not reduce antero-posterior (AP) sway compared to the situation in total darkness, but slightly reduced lateral sway at frequencies below 0.5 Hz. In contrast, fixating a stationary dot on a stationary large-field pattern reduced both AP and lateral body sway at all frequencies (0.1–2 Hz). Ocular tracking of the oscillating dot caused a peak in body sway at 1/3 Hz, i.e. the stimulus frequency, but there was no influence of large-field stimulus at this frequency. A stationary large-field pattern, however, reduced AP and lateral sway at frequencies between 0.1 and 2 Hz when subjects tracked a moving dot, compared to tracking in darkness. Our results demonstrate that a stationary large-field pattern has a stabilizing effect in all conditions, independent of whether the eyes are fixing on a stationary target or tracking a moving target.     

The Romberg ratio in people with multiple sclerosis

Postural control relies on the integration of inputs from the visual, somatosensory and vestibular systems which are frequently impaired in people with Multiple Sclerosis (PwMS). In this situation, examining the Romberg ratio can be useful. This parameter can be interpreted as a gross indicator of a vestibular and proprioceptive contribution to postural control. Therefore, the primary objective of the current study was to examine whether the Romberg ratio differs between MS fallers, non-fallers and neurological disability levels. In addition, we clarified the association between the Romberg ratio values with validated gait and the balance tests in PwMS. Romberg ratio values were calculated according to the sway rate, total sway area and center of pressure (CoP) path length. The patient group included 542 PwMS (337 women) with a mean age of 42.3 (S.D = 13.8). In terms of fall status, significant differences were observed between the faller (n = 287) and non-faller (n = 255) groups solely in terms of the Romberg ratio-ellipse sway area: 2.76 (S.D = 2.46) vs. 2.24 (S.D = 2.01), P-value = 0.01. A significant increase in the Romberg ratio was found between the severe group (n = 50), the very mild (n = 245), mild (n = 186) and moderate (n = 61) groups for each of the three Romberg ratio quotients. Significant weak correlation scores were found between the Romberg ratio-ellipse sway area and all walking and balance outcome measures; the Pearson’s rho ranged from 0.172 to 0.270. The present data suggest that an elevated Romberg ratio quotient, especially according to the sway area, is an indicator of poor walking and balance capabilities in PwMS.     

History of falls,balance performance,and quality of life in older cancer survivors

Older cancer survivors may be predisposed to falls because of the sequalae associated with cancer and its treatments. This study examined the association between the fall history, balance performance, and health‐related quality of life (QoL) in older, community‐dwelling cancer survivors who had completed primary cancer treatments. Forty-one cancer survivors (age = 67.9 ± 8.8 years) participated in the study. Balance performance was examined using the Activities-specific Balance Confidence Scale (ABC) and the Balance Evaluation Systems Test (BESTest). Scores from the Physical Component Summary (PCS) and Mental Component Summary (MCS) of the SF‐36v2 were obtained to assess the QoL. The demographics and health status were comparable between the fallers and non-fallers. While 54% of the participants had experienced at least one fall in the past 12 months, 30% had experienced two or more falls. Spearman's correlation analysis revealed a significant relationship between the outcomes from the ABC and the PCS (p < 0.001), and between the BESTest and the PCS (p < 0.001). Only the PCS significantly differentiated fallers from non-fallers (p < 0.01). Logistic regression analysis estimated that a one-unit increase in the PCS score significantly reduced the odds of falling by 13% (p < 0.01). The results demonstrate that in older cancer survivors, falls are a significant problem and balance control is a determinant of perceived physical function and well-being. Older cancer survivors reporting a poor QoL in the physical health domain may have higher risks of falling. Future studies are needed to examine the risk factor profiles of falls and the interventions to prevent falls in older cancer survivors.     

Use of ACE-inhibitors and falls in patients with Parkinson’s disease

Falls represent a major concern in patients with Parkinson’s disease (PD); however, currently acknowledged treatments for PD are not effective in reducing the risk of falling. The aim was to assess the association of use of ACE-inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) with falls among patients with PD.We analysed data of 194 elderly with PD attending a geriatric Day Hospital. Self-reported history of falls that occurred over the last year, as well as use of drugs, including ACEIs and angiotensin II receptor blockers (ARBs) were recorded. The association of the occurrence of any falls with use of ACEIs, and ARBs was assessed by logistic regression analysis. The association between the number of falls and use of ACEIs, and ARBs was assessed according to Poisson regression.In logistic regression, after adjusting for potential confounders, use of ACEIs was associated with a reduced probability of falling over the last year (OR = 0.15, 95% CI = 0.03–0.81; P = 0.028). This association did not vary with blood pressure levels (P for the interaction term = 0.528). Also, using Poisson regression, use of ACEIs predicted a reduced number of falls among participants who fell (PR = 0.31; 95% CI = 0.10–0.94; P = 0.039). No association was found between use of ARBs and falls.Our results indicate that use of ACEIs might be independently associated with reduced probability, and a reduced number of falls among patients with PD. Dedicated studies are needed to define the single agents and dosages that might most effectively reduce the risk of falling in clinical practice.     

Dynamic instability during post-stroke hemiparetic walking

Falls and fall-related injuries cause extremely costly and potentially fatal health problems in people post-stroke. However, there is no global indicator of walking instability for detecting which individuals will have increased risk of falls. The purposes of this study were to directly quantify walking stability in stroke survivors and neurologically intact controls and to determine which stability measures would reveal the changes in walking stability following stroke. This study thus provided an initial step to establish objective measures for identifying potential fallers. Nine post-stroke individuals and nine controls walked on a treadmill at four different speeds. We computed short-term local divergence exponent (LDE) and maximum Floquet multiplier (maxFM) of the trunk motion, average and variability of dynamic margins of stability (MOS) and step spatiotemporal measures. Post-stroke individuals demonstrated larger short-term LDE (p = 0.002) and maxFM (p = 0.041) in the mediolateral (ML) direction compared to the controls but remained orbitally stable (maxFM < 1). In addition, post-stroke individuals walked with greater average step width (p = 0.003) but similar average ML MOS (p = 0.154) compared to the controls. Post-stroke individuals also exhibited greater variability in all MOS and step measures (all p < 0.005). Our findings indicate that post-stroke individuals walked with greater local and orbital instability and gait variability than neurologically intact controls. The results suggest that short-term LDE of ML trunk motion and the variability of MOS and step spatiotemporal measures detect the changes in walking stability associated with stroke. These stability measures may have the potential for identifying those post-stroke individuals at increased risk of falls.     

Improvements in balance control in individuals with PCS detected following vestibular training: A case study

Concussed individuals have been found to experience balance deficits in the anterior-posterior (AP) direction as indicated by greater Center of Pressure (COP) displacement and velocity. One possible reason for this change in balance control could be due to damage to the lateral vestibulospinal tract which sends signals to control posterior muscles, specifically ankle extensors leading to compensatory torques about the ankle. The purpose of the study was to quantify balance assessments in individuals experiencing persistent post-concussion symptoms (PCS) to determine balance control changes following a vestibular training intervention. Participants (N = 6, >26 days symptomatic), were tested during their first appointment with a registered physiotherapist (PT) and during each follow up appointment. Participants were prescribed balance, visual, and neck strengthening exercises by the PT that were to be completed daily between bi-weekly appointments. Balance assessments were quantified using a Nintendo Wii board to record ground reaction forces. Participants completed 4 balance assessments: 1) Romberg stance eyes open (REO); 2) Romberg stance eyes closed (REC); 3) single leg stance eyes open (SEO); and 4) single leg stance eyes closed (SEC). The balance assessments were conducted on both a firm and compliant surfaces. Significant improvements in balance control were noted in ML/AP displacement and velocity of COP for both SEC and Foam REC conditions, with additional improvements in AP velocity of COP for Foam REC and in ML displacement of COP during Foam SEC. Overall, findings indicate that objectively quantifying balance changes for individuals experiencing persistent PCS allows for a more sensitive measure of balance and detects changes unrecognizable to the naked eye.     

The relationship between physical activity,and physical performance and psycho-cognitive functioning in older adults living in residential aged care facilities

Objectives

Insight into modifiable factors related to falls risk in older adults living in residential aged care facilities (RACFs) is necessary to tailor preventive strategies for this high-risk population. Associations between physical activity (PA), physical performance and psycho-cognitive functioning have been understudied in aged care residents. This study investigated associations between PA, and both physical performance and psycho-cognitive functioning in older adults living in RACFs.