Postural sway during quiet standing is related to physiological tremor and muscle volume in young and elderly adults

To examine the age-related deterioration in postural control, we investigated the association between postural sway during quiet standing and either amplitude of physiological tremor or muscle volume of the plantar flexors in 20 young and 20 elderly adults. They maintained a quiet standing position on a force platform for 60s with their eyes open or closed. During quiet standing, physiological tremors detected using a piezoresistive accelerometer were recorded from the soleus muscle, and the center of pressure (COP) displacement and body acceleration in the antero-posterior direction were calculated using the ground reaction forces as an assessment of postural sway. Muscle volume was predicted from muscle thickness by an ultrasonographic image. The physiological tremor of the soleus muscle during quiet standing was significantly greater in elderly than in young adults, and a positive association between physiological tremor and the amplitude of postural sway was found for young and elderly adults combined. Furthermore, physiological tremor was positively correlated with the high-frequency component of COP sway during quiet standing. A significantly negative relation between the muscle volume of the plantar flexors and postural sway was found in both age groups. These results suggest that physiological tremor reflects high-frequency fluctuations in postural sway during quiet standing in young and elderly adults, and age-related increases in the postural sway amplitude in the antero-posterior direction may be related to a decrease in muscle volume of the plantar flexors for maintaining an upright posture.     

Postural sway in children: A literature review

Background and aimStatic posturography can serve as an easy and fast way to determine whether a child possesses sufficient balance control in different sensory conditions. Therefore, the aim of this review is to map age-related differences in postural sway during childhood in typically developing children, using static posturography and to provide an overview of the available (age-specific) reference values in scientific literature.MethodsThe search strategy was performed in five databases (Pubmed, Web of Science, ScienceDirect, Cochrane Clinical Trials, Medline (Ovid)) November 2nd 2014 and updated twice: March 16th 2015 and July 20th 2015. The following keywords were used: (children OR child) AND (“postural control” OR “postural stability” OR equilibrium OR posture OR “postural balance”[mesh]) AND (“quiet stance” OR standing OR stance OR “quiet stance” OR static) AND (“postural sway” OR posturography OR “body sway” OR stabilography OR “trunk sway” OR “medio-lateral sway” OR “antero-posterior sway”). Relevant studies were identified using predefined selection criteria, applied on title and abstract (phase 1) and on full text (phase 2), supplemented with reference screening after the second phase.ResultsA total of 14 studies met the criteria. This review showed three main findings: 1) during natural bipedal stance with the eyes open, all studies reported a decrease in postural sway with increasing age, with conflicting results on the (non-)linearity of its development, 2) with eyes closed, all children show more sway than with eyes open and 3) only four studies reported numeric sway values that could serve as reference values, mainly focusing on children aged five and older.ConclusionConsiderable disagreement exists on the (non-)linearity of the development of postural sway in children. By choosing arbitrary age categories, it remains unclear between which age groups differences are situated. Future research is necessary to determine for which age groups age-specific reference values are relevant.     

Effects of initial foot position on postural responses to lateral standing surface perturbations in younger and older adults

BackgroundAn age-related decline in standing balance control in the medio-lateral direction is associated with increased risk of falls. A potential approach to improve postural stability is to change initial foot position (IFP).Research questionsIn response to a lateral surface perturbation, how are lower extremity muscle activation levels different and what are the effects of different IFPs on muscle activation patterns and postural stability in younger versus older adults?MethodsTen younger and ten older healthy adults participated in this study. Three IFPs were tested [Reference (REF): feet were placed parallel, shoulder-width apart; Toes-out with heels together (TOHT): heels together with toes pointing outward; Modified Semi-Tandem (M-ST): the heel of the anterior foot was placed by the big toe of the posterior foot]. Unexpected lateral translations of the standing surface were applied. Electromyographic (EMG) activity of the lower extremity muscles, standard deviation (SD) of the body’s CoM acceleration (SD of CoMAccel), and center of pressure (CoP) sway area were compared across IFPs and age.ResultsActivation levels of the muscles serving the ankle and gluteus medius were greater than for the knee joint muscles and gluteus maximus in the loaded leg across all IFPs in both groups. TOHT showed greater EMG peak amplitude of the soleus and fibularis longus compared to REF, and had smaller SD of CoMAccel and CoP sway area than M-ST. Compared to younger adults, older adults demonstrated lower EMG peak amplitude and delayed peak timing of the fibularis longus and greater SD of CoMAccel and CoP sway area in all IFPs during balance recovery.SignificanceDuring standing balance recovery, ankle muscles and gluteus medius are important active responders to unexpected lateral surface perturbations and a toes-out IFP could be a viable option to enhance ankle muscle activation that diminishes with age to improve postural stability.     

Age-related changes in human postural control of prolonged standing

The aim of this study was to characterize prolonged standing and its effect on postural control in elderly individuals in comparison to adults. It is unknown how elderly individuals behave during prolonged standing and how demanding such a task is for them. We recorded the center of pressure (COP) position of 14 elderly subjects and 14 adults while they performed prolonged standing (30 min) and quiet stance tasks (60 s) on a force plate. The number and amplitude of the COP patterns, the root mean square (RMS), speed, and frequency of the COP sway were analyzed. The elderly subjects were able to stand for prolonged periods but they produced postural changes of lesser amplitude and a decreased sway during the prolonged standing task. Both the adults and the elderly subjects were influenced by the prolonged standing task, as demonstrated by their increased COP RMS and COP speed in the quiet standing trial after the prolonged standing task, in comparison to the trial before. We suggest that the lack of mobility in elderly subjects may be responsible for the observed sub-optimal postural changes in this group. The inability of elderly individuals to generate similar responses to adults during prolonged standing may contribute to the increased risk of falls in the older population.     

Postural control development from late childhood through young adulthood

BackgroundThe development of stable postural control is characterized by changes in sway variability and periods of rapid reorganization of motor system components.Research questionThe current study examined whether changing biomechanical and perceptual demands influences the postural control behavior during development.MethodThe center of pressure (COP) was assessed via a cross-sectional design. Data were collected from 48 females in three age groups (late childhood, mid-adolescence, and young adulthood) during four quiet stance conditions: (1) eyes open with feet apart, (2) eyes open with feet together, (3) eyes closed with feet apart, and (4) eyes closed with feet together. Linear measures included total path length of the COP and the mean/standard deviation of the overall COP position and speed. To characterize the sway patterns via nonlinear analyses, the speed and two-dimensional positional time series were submitted to sample entropy and Renyi entropy, respectively.ResultsThe linear results indicated that the late childhood group displayed longer COP trajectories (p < .001) and faster and more variable COP speed (p’s < .001). These results held for both the feet apart and feet together conditions, independent of vision. The nonlinear results indicated that the late childhood group exhibited less regularity, overall, in their COP sway position (i.e., Renyi entropy) compared to the two older groups in the feet apart condition (p’s ≤ .041), and to the young adults in the feet together condition, independent of vision (p < .001). However, the mid-adolescent group demonstrated greater regularity in their COP speed (i.e., sample entropy) when their eyes were closed compared to the other two groups, independent of stance (p’s < .05).SignificanceThe linear results support previous findings, while the nonlinear measures indicate sway characteristics that may provide a window into the development of underlying control processes that regulate quiet standing.     

The role of spatial alignment in posture-cognition dual task interaction

BackgroundA range of cognitive tasks can interfere with postural control, particularly in older adults. In the case of spatial tasks, the spatial alignment between the task and postural control can incur dual-task costs separately from task load. It has been suggested that spatial tasks incur dual-task costs because accessing the visuospatial sketchpad component of working memory reduces the capacity to utilize external visual information for postural control.Research questionWe investigated whether the spatial alignment between a cognitive and a postural control task can affect postural stability even when visual perception is not involved in either task and task load does not differ between aligned and non-aligned conditions. We predicted that any such effect would be greater in older people and in a more challenging stance.MethodsFifty healthy adults (27 aged 20–35, 23 aged 59–88) with no history of balance or cognitive difficulties performed a mental navigation task while standing in open or closed stance with eyes closed. The mental navigation task was presented in a reference plane that was either aligned or non-aligned to the horizontal reference plane in which the posture control system controlled the position of the body’s center of gravity. Task performance was measured as accuracy and response time and postural sway as anteroposterior (AP) and mediolateral (ML) sway velocity.ResultsThe older group were less accurate in the mental navigation task, and both groups had higher AP and ML sway velocity in closed stance. When standing in the more challenging stance, the older group had higher AP sway velocity while performing the mental navigation task in the non-aligned than the aligned reference plane condition.SignificanceThe spatial configuration compatibility between a cognitive task and postural control can affect postural stability even when visual information is not being used for either task and task load is unchanged.     

Age-related changes in human postural control of prolonged standing

The aim of this study was to characterize prolonged standing and its effect on postural control in elderly individuals in comparison to adults. It is unknown how elderly individuals behave during prolonged standing and how demanding such a task is for them. We recorded the center of pressure (COP) position of 14 elderly subjects and 14 adults while they performed prolonged standing (30 min) and quiet stance tasks (60 s) on a force plate. The number and amplitude of the COP patterns, the root mean square (RMS), speed, and frequency of the COP sway were analyzed. The elderly subjects were able to stand for prolonged periods but they produced postural changes of lesser amplitude and a decreased sway during the prolonged standing task. Both the adults and the elderly subjects were influenced by the prolonged standing task, as demonstrated by their increased COP RMS and COP speed in the quiet standing trial after the prolonged standing task, in comparison to the trial before. We suggest that the lack of mobility in elderly subjects may be responsible for the observed sub-optimal postural changes in this group. The inability of elderly individuals to generate similar responses to adults during prolonged standing may contribute to the increased risk of falls in the older population.     

Normative database of postural sway measures using inertial sensors in typically developing children and young adults

ObjectiveReference values utilizing the APDM MobilityLab® inertial sensor system have not been established in children and young adults ages 5−30. These values are necessary for clinicians and researchers to compare to children with balance impairments.MethodsA group of 144 typically developing children and young adults from age 5–30 years completed the instrumented SWAY test during 6 test conditions: normal stance, firm surface, eyes open (EO) and closed (EC); normal stance, foam surface, EO and EC; and tandem stance, firm surface, EO and EC. Selected variables for normative outcomes included total sway area, and the mean, sagittal and coronal values for RMS sway, jerk, sway velocity and path length. Sex differences were examined within age groups via t tests. The effect of age on postural sway variables was analyzed using a one-way ANOVA for the mean values of total sway area, RMS sway, velocity and jerk, followed by post-hoc pairwise comparisons.ResultsAll sway parameters decreased significantly with age (p < 0.0001). Adult-like total sway area and jerk were achieved by ages 9−10 except for jerk during EC on foam. RMS sway and sway velocity reached adult levels by ages 11−13 during all EO and tandem stance conditions, and 14−21 with EC during normal stance on firm and foam surfaces for RMS sway and EC on firm surfaces for velocity. Females ages 5−6 performed more poorly during EO firm and EC foam for certain variables, but better during EO tandem and females ages 7–13 outperformed males when sex differences were found.SignificanceThese reference values can now be used by clinicians and researchers to evaluate abnormal postural sway and response to interventions in children and young adults.     

Association of postural balance and falls in adult patients receiving haemodialysis: A prospective cohort study

BackgroundStatic postural balance performance is often impaired in people receiving haemodialysis (HD) for the treatment of stage-5 chronic kidney disease (CKD-5). However, the question as to whether lower postural balance is associated with adverse clinical outcomes such as falls has not been addressed yet.Research questionWe conducted a prospective cohort study to explore the association between static postural balance and falls in people receiving HD. We hypothesised that higher postural sway would be associated with increased odds of falling.MethodsSeventy-five prevalent CKD-5 patients receiving HD (age: 61.8 ± 13.4 years) from three Renal Units were enrolled in this prospective cohort study. At baseline, postural balance was assessed with a force platform in eyes open (EO) and eyes closed (EC) conditions. Centre of pressure (CoP) measures of range, velocity and area were taken for the analysis. Falls experienced by study participants were prospectively recorded during 12 months of follow-up. Secondary outcomes included timed-up and go, five-repetition sit-to-stand test and the Tinetti falls efficacy scale (FES).ResultsIn multivariable logistic regression analysis, higher CoP range in medial-lateral direction during EC was associated with increased odds of falling (OR: 1.04, 95 %CI: 1.00−1.07, p = 0.036). In ROC curve analysis, CoP velocity in EO exhibited the greatest prognostic accuracy (AUC: 0.69, 95 %CI: 0.55−0.82), however this was not statistically different from CoP measures of area and range. None of the postural balance measures exceeded the prognostic accuracy of the FES (AUC: 0.70, 95 %CI: 0.58−0.83, p = 0.005).SignificanceThis prospective cohort study showed that higher postural sway in medial-lateral direction was associated with increased odds of falling in people receiving HD. CoP measures of range, velocity and area displayed similar prognostic value in discriminating fallers from non-fallers. The overall utility of static posturography to detect future fall-risk may be limited in a clinical setting.     

Motor dual task with eyes closed improves postural control in patients with functional motor disorders: A posturographic study

BackgroundFunctional motor disorders (FMD) are highly disabling neurological conditions in which postural control deficits increase the risk of falls and disability in performing daily living activities. Scattered evidence suggests that such disturbances may depend on abnormal attentional focus and might improve with distraction.Research questionHow do motor and cognitive dual tasks performed under two different sensory conditions shape postural control in patients with FMD.MethodsThis posturographic study involved 30 patients with FMD (age, 45.20 ± 14.57 years) and 30 healthy controls (age, 41.20 ± 16.50 years). Postural parameters were measured with eyes open, and eyes closed in quiet stance (single task) and on a motor dual task (m-DT) and a calculation (cognitive) dual task (c-DT). The dual task effect (DTE, expressed in percentage) on motor and cognitive performance was calculated for sway area, length of Center of Pressure (CoP), and velocity of CoP displacement.ResultsThere was a statistically significant three-way interaction between task, condition, and group for the DTE on sway area (p = 0.03). The mean sway area DTE on the motor task in the eyes-closed condition was increased by 70.4 % in the healthy controls, while it was decreased by 1% in the patient group (p = 0.003). No significant three-way interaction was observed for the DTE on length of CoP and velocity of CoP displacement.SignificanceThis study provides novel preliminary evidence for the benefit of a simple motor dual task in the eyes closed condition as a way to improve postural control in patients with FMD. These findings are relevant for the management of postural control disorders in patients with FMD.     

The effect of cervical spine subtypes on center of pressure parameters in a large asymptomatic young adult population

BackgroundRecent research highlighted that non-lordotic subtypes are common within an asymptomatic population of young adults. The potential mechanisms responsible for the decreased postural control witnessed in healthy participants exhibiting non-lordotic cervical alignment are unclear.Research questionTherefore, the aim of this study is to compare and contrast asymptomatic radiographically derived sagittal cervical alignment subtypes with Center of Pressure (CoP) parameters.MethodsIn this cross-sectional study strict asymptomatic inclusion criteria were met by 150 of the original 182 volunteers. All radiographs were assessed using a multi-method subtype system with participants classified into lordotic and non-lordotic groups. Participants performed 90s narrow stance trials with their eyes closed whilst standing on both a firm surface (FS) and compliant surface (CS) (3 trials per surface). CoP parameters were recorded from a force platform sampling at 100 Hz. Nonparametric statistical tests were conducted to assess differences between groups for each surface type and to determine differences in CoP parameters between FS and CS types.ResultsSignificant differences were found between groups on both surfaces for the anterior to posterior range (FS: p = 0.013; CS: p = 0.023), total excursion (FS: p = 0.029; CS: p = 0.005) and mean velocity of total excursion (FS: p = 0.032; CS: p = 0.004).SignificanceOur data suggest that sagittal plane cervical alignment is a measure capable of distinguishing between the postural control of asymptomatic lordotic and non-lordotic young adult participants on both surfaces types. Furthermore, decreased postural control is present in asymptomatic participants across all non-lordotic subtypes and is not isolated exclusively to those with forward head posture. Consequently, future research endeavours should investigate the clinical significance of these non-lordotic findings in relation to both the potential for early cervical osseous degeneration and the transitional stages of non-specific pain sufferers from previously asymptomatic young adults.     

Differences in lower extremity muscular coactivation during postural control between healthy and obese adults

IntroductionIt is well established that obesity is associated with deterioration in postural control that may reduce obese adults’ autonomy and increase risks of falls. However, neuromuscular mechanisms through which postural control alterations occur in obese adults remain unclear.ObjectiveTo investigate the effects of obesity on muscle coactivation at the ankle joint during static and dynamic postural control.Materials and methodsA control group (CG; n = 20; age = 32.5 ± 7.6 years; BMI = 22.4 ± 2.2 Kg/m²) and an obese group (OG; n = 20; age = 34.2 ± 5.6 years; BMI = 38.6 ± 4.1 Kg/m²) participated in this study. Static postural control was evaluated by center of pressure (CoP) displacements during quiet standing. Dynamic postural control was assessed by the maximal distance traveled by the CoP during a forward lean test. Electromyography activity data for the gastrocnemius medialis (GM), soleus (SOL) and tibialis anterior (TA) were collected during both quiet standing and forward lean tests. Muscle activities were used to calculate two separate coactivation indexes (CI) between ankle plantar and dorsal flexors (GM/TA and SOL/TA, respectively).ResultsCoP displacements were higher in the OG than in the CG for quiet standing (p < 0.05). When leaning forward, the maximal distance of the CoP was higher in the CG than in the OG (p < 0.05). Only the CI value calculated for SOL/TA was higher in the OG than in the CG for both static and dynamic tasks (p < 0.05). The SOL/TA CI value in the OG was positively correlated with CoP displacements during quiet standing (r = 0.79; p < 0.05).ConclusionObesity increases muscle coactivation of the soleus and tibialis anterior muscles at the ankle joint during both static and dynamic postural control. This adaptive neuromuscular response may represent a joint stiffening strategy for enhancing stability. Consequently, increased ankle muscle coactivation could not be considered as a good adaptation in obese adults.     

Effects of subthreshold electrical stimulation with white noise,pink noise,and chaotic signals on postural control during quiet standing

BackgroundThe stochastic resonance (SR) phenomenon has been used to improve postural control through the application of imperceptible noise to the somatosensory system. White noise signals have been applied in numerous SR studies on postural control. However, because the SR effect depends on the noise structure, the stimulation effects of signals with different structures, such as pink noise and chaotic signals, on postural control, must be determined to achieve better clinical applications of SR technology.Research questionDuring quiet standing, how is postural control affected by subthreshold electrical stimulation to the knee joints when signals with different structures (white noise, pink noise, and chaotic signals) are used?MethodsSixteen healthy young adults stood quietly for 40 s with their eyes closed. To evaluate postural sway, we calculated the mean velocity, root mean square (CoP_RMS), and range (CoP_Range) values for the center of pressure (CoP) in the anteroposterior direction. The standing task was conducted under subthreshold electrical stimulation with white noise, pink noise, and chaotic signals based on the Lorenz system, in addition to the no-stimulation condition. The four stimulation conditions were randomized within each set and repeated seven times.ResultsSignificant effects of stimulation were observed in the CoP_RMS and CoP_Range values. The CoP_RMS value under the pink noise signal was significantly lower than that under the no-stimulation condition. The CoP_Range value also tended to decrease under the pink noise signal compared with the no-stimulation condition; however, the differences were not statistically significant. No significant changes were found with the white noise and chaotic signals compared with the no-stimulation condition.SignificanceWe demonstrated that the pink noise signal was more effective in reducing postural sway than the white noise and chaotic signals based on the Lorenz system during quiet standing.     

Relationship between postural sway on an unstable platform and ankle plantar flexor force steadiness in community-dwelling older women

BackgroundForce steadiness is evaluated as force variability during constant force exertion around a target level. Ankle plantar flexor force steadiness is reported to be related to postural sway on an unstable platform in healthy young adults; however, this relationship in older adults is unclear.Research questionThis study aimed to investigate whether ankle plantar flexor force steadiness was related to postural sway on stable and unstable platforms in older adults.MethodsTwenty-six community-dwelling older women participated in this study (72 ± 6 years). Maximal isometric strength and force steadiness at 5%, 20 %, and 50 % of the maximal strength of ankle plantar flexion were assessed. Postural sway in the anteroposterior direction during bipedal standing was measured on stable and unstable platforms.ResultsThe results showed that force steadiness at any intensity level and maximal isometric strength were not related to postural sway on the stable platform. Force steadiness at 20 % of maximal strength alone was significantly correlated with postural sway on the unstable platform (ρ = 0.441, p < 0.05).SignificanceThese results indicate that the ability to control muscle force could be important for postural stability on an unstable platform in older adults.     

The influence of ambient lighting levels on postural sway in healthy children

The purpose of this study was to determine whether postural sway in healthy children varied in different levels of ambient lighting. Twelve boys and 26 girls with a mean age of 118 months stood on a force platform under three conditions: eyes closed, eyes opened in regular light (200 lx) and eyes opened in dim light (3 lx). Analysis of variance and pairwise comparisons revealed significantly more postural sway with the eyes closed condition compared to the regular and dim light conditions but no differences between the regular and dim light conditions. While our results on postural sway during the eyes closed condition are consistent with current findings in the pediatric and adult literature, our findings comparing postural sway during regular and dim light conditions differ from those found in older adults. It appears that the visual system of children is efficient in dim light conditions, adding support to the view that quiet standing is more dependent on vision in older adults than in younger individuals.     

Effect of individualized cognitive and postural task difficulty levels on postural control during dual task condition

BackgroundPrevious dual task studies suggested that the difficulty of the concurrent cognitive and motor tasks may not be challenging to the same degree for each person. This study approaches this problem by setting individualized difficulty levels for tasks to examine the dual task interference.Research questionDo the features of postural sway depend on increased individualized difficulty levels of concurrent cognitive and postural activities?Methods20 young healthy participants (10 male, 10 female) took part in the study. Before the experiments, cognitive task difficulty (No-, Medium-, High) has been set individually. Subjects performed postural tasks (quiet stance, voluntary sway) concurrently with or without a cognitive task which based on simple arithmetic calculations. Postural sway features were examined.ResultsPostural sway features were affected by individualized difficulty level of concurrent cognitive and postural activities. In voluntary sway, as a more challenging postural task, higher reductions were observed for such sway features as COP velocity and range in AP direction.SignificanceThis study signaled task-specific changes in postural sway features. When the difficulty levels were set individually, the effect of motor and cognitive dual task was more apparent when the balance requirement of the primary motor task increased.     

Athletic skill level is reflected in body sway: A test case for accelometry in combination with stochastic dynamics

Recent studies on postural control have shown that the variability of body sway during quiet standing may provide valuable information to characterize changes in postural control due to age, pathology, skill and task. The aim of the present study was to determine – as spade work for possible clinical applications – whether body sway measured with a three-axial accelerometer at the trunk can differentiate between three healthy young populations that differ in athletic skill level. The three groups in question (group size: n = 22) consisted of regular bachelor students, physical education students and physical education students specialized in gymnastics. Data were recorded during tandem stance with eyes open or closed and while standing on foam. The acceleration time-series were analysed in anteriorposterior and mediolateral direction. Differences in postural control were quantified in terms of variability, spectral properties and stochastic dynamical measures, i.c., regularity (sample entropy, long-range correlations) and local stability (largest Lyapunov exponent). The results were clear-cut. Standing with eyes closed and on foam increased variability. Compared to standing with eyes open, standing with eyes closed resulted in less regular sway patterns but with greater local stability, whereas standing on foam had an opposite effect. With greater gymnastic skills, acceleration time-series were less variable, less regular and more stable. These results imply that quantifying the stochastic-dynamical structure of postural sway using ambulant accelerometry may provide a useful diagnostic tool.     

Impaired postural control of axial segments in children with cerebral palsy

BackgroundSensorimotor control of axial segments, which develops during childhood and is not mature until adolescence, is essential for the development of balance control during motor activities. Children with cerebral palsy (CP) have deficits in postural control when standing or walking, including less stabilization of the head and trunk which could affect postural control.Research questionIs dynamic stabilization of axial segments during an unstable sitting task deficient in children with CP compared to typically developing children? Is this deficit correlated with the deficit of postural control during standing?MethodSeventeen children with CP (GMFCS I-II) and 17 typically-developing children from 6 to 12 years old were rated on the Trunk Control Measurement Scale (TCMS). In addition, posturography was evaluated in participants while they maintained their balance in stable sitting, unstable sitting, and quiet standing, under “eyes open” and “eyes closed” conditions. In sitting tasks, the participants had to remain stable while being prevented from using the lower and upper limbs (i.e. to ensure the involvement of axial segments alone).ResultsChildren with CP compared to TD children had significantly larger surface area, mean velocity and RMS values of CoP displacements measured during the unstable sitting task and the standing task, under both “eyes open” and “eyes closed” conditions. No significant group effects were observed during the stable sitting task. The TCMS total score was significantly lower, indicating trunk postural deficit, in the CP group than in the TD group and was significantly correlated with postural variables in the sitting and standing tasks.SignificanceChildren with CP indeed have a specific impairment in the postural control of axial segments. Since the postural control of axial segments is important for standing and walking, its impairment should be taken into account in rehabilitation programs for children with CP.     

Auditory cues behind congenitally blind subjects improve their balance control in bipedal upright posture

BackgroundCongenitally blind subjects developed postural adaptations improving somatosensory and vestibular systems to maintain upright stability and auditory skills to orient them in environment. However, the influence of auditory cues on upright stability in congenitally blind subjects stays unknown.Research questionThe aim of this study is to define the influence of an auditory cue in congenitally blind subjects back space on their balance posture.MethodsEleven sighted subjects and eleven congenitally blind subjects performed upright bipedal and unipedal quiet stances on a force plate with two conditions of auditory cue played by a loudspeaker placed 2 m behind them. Mean CoP velocity were recorded. Student test was used to compare significant difference between blind and sighted subjects bipedal and unipedal postures stability in both conditions of auditory cue.Results and significanceResults showed that congenitally blind subjects had no significant difference in mean sway velocity compared to sighted subjects in bipedal upright posture in auditory signal condition. However, blind subjects had significant lower mean sway velocity than sighted subjects in bipedal upright posture without sound. Blind subjects had significant increased mean sway velocity during unipedal quiet standing in both auditory cue conditions (with and without sound). The results showed that congenitally blind subjects used auditory cues placed behind them in order to improve their balance control in bipedal upright posture. In this case, blind subjects could better use compensatory mechanisms to perform quiet standing as sighted subjects. Without sound or in unipedal upright posture, congenitally blind subjects probably have sensory perturbations or limitations that impose them adaptations in order to avoid falling risk. Auditory cues should be study in the aim to better understand the compensatory mechanisms used by congenitally blind subjects to perform postural balance in usual environment.