Balance Control Task Research Articles

Balance Control Deficits are Associated With Diminished Ankle Force Sense, Not Position Sense, in Athletes With Chronic Ankle Instability

ObjectivesTo compare balance control and ankle proprioception between athletes with and without chronic ankle instability (CAI). A further objective was to explore the relationship between balance control performance and ankle proprioception in athletes with CAI. DesignCross-sectional study. SettingsSports Rehabilitation Laboratory. ParticipantsEighty-eight recreational athletes (47 CAI and 41 healthy control) were recruited. InterventionsNo applicable. Main Outcome MeasuresBalance control performance was assessed using the sway velocity of the center of the pressure during the one-leg standing tasks. Ankle proprioception, including joint position sense and force sense, were tested using absolute error (AE) associated with joint position reproduction and force reproduction tasks in 4 directions, that is, plantarflexion, dorsiflexion, inversion, and eversion. ResultsAthletes with CAI performed significantly worse than those without CAI in balance control tasks. In addition, CAI athletes showed significantly worse joint position sense and force sense in all 3 movement directions tested (plantarflexion, inversion, and eversion). Correlation analysis showed that the AE of the plantarflexion force sense was significantly moderately correlated with medial-lateral sway velocity in the one-leg standing with eyes open and closed conditions (r=.372-.403, P=.006-.012), and the AE of inversion force sense was significantly moderately correlated with medial-lateral sway velocity in the one-leg standing with eyes open (r=.345, P=.018) in athletes with CAI, but the joint position sense measures were not (all P>0.05). ConclusionsAthletes with CAI showed significantly impaired balance control performance and diminished ankle proprioception. Deficit in force sense was deemed as a moderate predictor of one-leg standing balance control deficits in athletes with dominant-side injury CAI, whereas ankle position sense may be a small predictor.

Trunk Instability in the Pitch, Yaw, and Roll Planes during Clinical Balance Tests: Axis Differences and Correlations to vHIT Asymmetries Following Acute Unilateral Vestibular Loss.

Clinical dynamic posturography concentrates on the pitch and roll but not on the yaw plane instability measures. This emphasis may not represent the axis instability observed in clinical stance and gait tasks for patients with balance deficits in comparison to healthy control (HC) subjects, nor the expected instability based on correlations with vestibulo-ocular reflex (VOR) deficits. To examine the axis stability changes with vestibular loss, we measured trunk sway in all three directions (pitch, roll, and yaw) during the stance and gait tasks of patients with acute unilateral vestibular neuritis (aUVN) and compared the results with those of HC. Concurrent changes in VORs were also examined and correlated with trunk balance deficits. The results of 11 patients (mean age of 61 years) recorded within 6 days of aUVN onset were compared within those of 8 age-matched healthy controls (HCs). All subjects performed a two-legged stance task-standing with eyes closed on foam (s2ecf), a semi-gait task-walking eight tandem steps (tan8), and four gait tasks-walking 3 m with head rotating laterally, pitching, or eyes closed (w3hr, w3hp, w3ec), and walking over four barriers 24 cm high, spaced 1 m apart (barr). The tasks' peak-to-peak yaw, pitch and roll angles, and angular velocities were measured with a gyroscope system (SwayStarTM) mounted at L1-3 and combined into three, axis-specific, balance control indexes (BCI), using angles (a) for the tandem gait and barriers task, and angular velocities (v) for all other tasks, as follows: axis BCI = (2 × 2ecf)v + 1.5 × (w3hr + w3hp + w3ec)v + (tan8 + 12 × barr)a. Yaw and pitch BCIs were significantly (p ≤ 0.004) greater (88 and 30%, respectively) than roll BCIs for aUVN patients. For HCs, only yaw but not pitch BCIs were greater (p = 0.002) than those of roll (72%). The order of BCI aUVN vs. HC differences was pitch, yaw, and roll at 55, 44, and 31%, respectively (p ≤ 0.002). This difference with respect to roll corresponded to the known greater yaw plane than roll plane asymmetry (40 vs. 22%) following aUVN based on VOR responses. However, the lower pitch plane asymmetry (3.5%) in VOR responses did not correspond with the pitch plane instability observed in the balance control tests. The increases in pitch plane instability in UVL subjects were, however, highly correlated with those of roll and yaw. These results indicate that greater yaw than pitch and roll trunk motion during clinical balance tasks is common for aUVN patients and HCs. However, aUVN leads to a larger increase in pitch than yaw plane instability and a smaller increase in roll plane instability. This difference with respect to roll corresponds to the known greater yaw plane than roll plane asymmetry (40 vs. 22%) following aUVN observed in VOR responses. However, the lower pitch plane asymmetry (3.5%) in VOR responses does not correspond with the enhanced movements in the pitch plane, observed in balance control tasks. Whether asymmetries in vestibular-evoked myogenic potentials (Vemps) are better correlated with the deficits in pitch plane balance control remains to be investigated. The current results provide a strong rationale for the clinical testing of directional specific balance responses, especially yaw and pitch, and the linking of balance results for yaw and roll to VOR asymmetries.

Gyroscopic Balancer-Enhanced Motion Control of an Autonomous Bikebot

Abstract Bikebot (i.e., bicycle-based robot) is a class of underactuated balance robotic systems that require simultaneous trajectory tracking and balance control tasks. We present a tracking and balance control design of an autonomous bikebot. The external-internal convertible structure of the bikebot dynamics is used to design a causal feedback control to achieve both the tracking and balance tasks. A balance equilibrium manifold is used to define and capture the platform balance profiles and coupled interaction with the trajectory tracking performance. To achieve fully autonomous navigation, a gyrobalancer actuation is integrated with the steering and velocity control for stationary platform balance and stationary-moving switching. Stability and convergence analyses are presented to guarantee the control performance. Extensive experiments are presented to validate and demonstrate the autonomous control design. We also compare the autonomous control performance with human riding experiments and similar action strategies are found between them.

Neural underpinnings of freezing-related dynamic balance control in people with Parkinson's disease

IntroductionPeople with Parkinson's disease (PD) with freezing of gait (FOG; freezers) show impaired dynamic balance and experience falls more frequently compared to those without (non-freezers). Here, we explore the neural underpinnings of these freezing-related balance problems. Methods12 freezers, 16 non-freezers and 14 controls performed a dynamic balance task in the lab. The next day, the same task was investigated in the MRI-scanner through motor imagery (MI). A visual imagery (VI) control task was also performed. Imagery engagement was determined by comparing the performance times between the dynamic balance task, and its MI- and VI-variants. Balance-related brain activations in regions of interest were contrasted between groups based on an MI > rest versus VI > rest contrast. ResultsFreezers and non-freezers were matched for age, cognition and disease severity. Similar performance times between the balance control task and the MI-conditions revealed excellent imagery engagement. Compared to non-freezers, freezers showed decreased activation in regions of interest located in the left mesencephalic locomotor region (MLR; p = 0.006), right anterior cerebellum (p = 0.017) and cerebellar vermis (p < 0.001). Intriguingly, non-freezers showed higher activations in the cerebellar vermis than controls (p = 0.010). ConclusionOverall, we showed that decreased activation in the left MLR, and cerebellar regions in freezers relative to non-freezers could explain why dynamic balance is more affected in freezers. As non-freezers displayed increased cerebellar vermis activation compared to controls, it is possible that freezers show an inability to recruit sufficient compensatory cerebellar activity for effective dynamic balance control.

Cerebello-cortical functional connectivity may regulate reactive balance control in older adults with mild cognitive impairment.

Older adults with mild cognitive impairment (OAwMCI) experience a two-fold increased risk of falling compared to their cognitively intact counterparts. This increased risk could be attributed to impairments in balance control mechanisms (both volitional and reactive), however, the exact neural substrates contributing to the balance impairments remain unclear. While changes in functional connectivity (FC) networks in volitional balance control tasks have been well highlighted, the relationship between these changes and reactive balance control has not been examined. Therefore, this study aims to explore the relationship between FC networks of the brain obtained during resting state fMRI (no visualization or active task performed) and behavioral measures on a reactive balance task in OAwMCI. Eleven OAwMCI (< 25/30 on MoCA, > 55 years) underwent fMRI and were exposed to slip-like perturbations on the Activestep treadmill. Postural stability, i.e., dynamic center of mass motion state (i.e., its position and velocity) was computed to determine reactive balance control performance. The relationship between reactive stability and FC networks was explored using the CONN software. OAwMCI with greater FC in default mode network-cerebellum (r2 = 0.43, p < 0.05), and sensorimotor-cerebellum (r2 = 0.41, p < 0.05) network exhibited lower reactive stability. Further, people with lower FC in middle frontal gyrus-cerebellum (r2 = 0.37, p < 0.05), frontoparietal-cerebellum (r2 = 0.79, p < 0.05) and cerebellar network-brainstem (r2 = 0.49, p < 0.05) exhibited lower reactive stability. Older adults with mild cognitive impairment demonstrate significant associations between reactive balance control and cortico-subcortical regions involved in cognitive-motor control. Results indicate that the cerebellum and its communications with higher cortical centers could be potential substrates contributing to impaired reactive responses in OAwMCI.

Wearable Devices and Smartphone Inertial Sensors for Static Balance Assessment: A Concurrent Validity Study in Young Adult Population.

Falls represent a public health issue around the world and prevention is an important part of the politics of many countries. The standard method of evaluating balance is posturography using a force platform, which has high financial costs. Other instruments, such as portable devices and smartphones, have been evaluated as low-cost alternatives to the screening of balance control. Although smartphones and wearables have different sizes, shapes, and weights, they have been systematically validated for static balance control tasks. Different studies have applied different experimental configurations to validate the inertial measurements obtained by these devices. We aim to evaluate the concurrent validity of a smartphone and a portable device for the evaluation of static balance control in the same group of participants. Twenty-six healthy and young subjects comprised the sample. The validity for static balance control evaluation of built-in accelerometers inside portable smartphone and wearable devices was tested considering force platform recordings as a gold standard for comparisons. A linear correlation (r) between the quantitative variables obtained from the inertial sensors and the force platform was used as an indicator of the concurrent validity. Reliability of the measures was calculated using Intraclass correlation in a subsample (n = 14). Smartphones had 11 out of 12 variables with significant moderate to very high correlation (r > 0.5, p < 0.05) with force platform variables in open eyes, closed eyes, and unipedal conditions, while wearable devices had 8 out of 12 variables with moderate to very high correlation (r > 0.5, p < 0.05) with force platform variables under the same task conditions. Significant reliabilities were found in closed eye conditions for smartphones and wearables. The smartphone and wearable devices had concurrent validity for the static balance evaluation and the smartphone had better validity results than the wearables for the static balance evaluation.

Electromyography Based Analysis of the Impact of Ageing on Muscle Activation Pattern during Static and Dynamic Balance Control Tasks: A Systematic Review

The present systematic review was done, to examine the impact of aging on posture control mechanisms in terms of muscle activity and sway patterns. English language articles describing effects of aging on muscle activation pattern during balance control tasks using electromyography methods published from 2000 to 2019 were identified. Studies were compared with regards to study population, postural tasks, perturbations, muscle inclusion, and outcome measures. All the included studies (N-9) exhibited increased postural sway among elderly in contrast to young population. In contrast, inconsistency was observed in the muscle activation pattern, muscle dependency, and muscle co-contractions among the studies. Altogether, the findings of the review suggest that the aging causes alterations in muscle activity in order to maintain balance during challenging situations; however, the studies do not elucidate these changes across the ages.

EEG-explained cortical correlates of transfemoral amputees during balancing with vibrotactile feedback: A pilot study

Improving postural stability of lower limb amputees by integrating vibrotactile sensory feedback (VF) with balancing exercises has been proved advantageous. However, the cortical processes engaged in human balance control which process the VF and help to improve postural stability remain elusive. To this end, Electroencephalography in synchronization with the center of pressure (CoP) signals was collected from six transfemoral amputees during a balance control task in two sessions: with and without VF. The improved limit of stability (LOS) during the balance task with VF was in response to elicited strong theta and gamma oscillations. The secondary somatosensory cortex-S2 (contralateral to amputated side) processes the sensory information from VF by significantly reducing the theta spectral power. Additionally, the fronto-central (FC) region executed the motor response to improve the LOS by significantly increasing the gamma power. The intra-regional functional-connectivity at the S2 and FC region was significantly stronger with VF, in comparison to no feedback condition, and the two regions (S2 and FC) were strongly connected while perceiving the VF during forward voluntary sway in comparison to no feedback sessions. These findings provide fundamental insights into the cortical activity associated with the VF and helps in understanding the cortical mechanism of balance improvement in transfemoral amputees.

EEG based cortical investigation for the limit of stability analysis in transfemoral amputees: A comparison with able-bodied individuals

BackgroundThe evidences for demonstrating the contributions of the cerebral cortex in human postural control is increasing. However, there remain little insights about the cortical correlates of balance control in lower-limb amputees. The present study aimed to investigate the cortical activity and balance performance of transfemoral amputees in comparison to healthy individuals during a continuous balance task (CBT). MethodsThe postural stability of the participants was defined with limit of stability parameter. Electroencephalography (EEG) data were recorded in synchronization with the center of pressure (CoP) data from eighteen individuals (including eight unilateral transfemoral amputees). We anticipated that, due to the limb loss, the postural demand of transfemoral amputees increases which significantly modulates the spectral power of intrinsic cortical oscillations. FindingsUsing the independent components from the sensorimotor areas and supplementary motor area (SMA), our results present a well-pronounced drop of alpha spectral power at sensorimotor area contralateral to sound limb of amputees in comparison to SMA and the sensorimotor area contralateral to prosthetic limb. Following this, we found significantly higher (p < 0.05) limit of stability (LOS) at their sound limb than at the prosthetic limb. Healthy individuals have similar contribution from both the limbs and the EEG alpha spectral power was similar across the three regions of the cortex during the balance control task as expected. Overall, a decent correlation was found between the LOS and alpha spectral power in both amputee and healthy individuals (Pearson’s correlation coefficient > 0.5). InterpretationBy externally stimulating the highlighted cortical regions, neuroplasticity might be promoted which helps to reduce the training time for the efficient rehabilitation of amputees. Additionally, this new knowledge might benefit in the designing and development of innovative interventions to prevent falls due to lower limb amputation.

Does instructing attentional focus direction affect static single leg balance performance?

Balance and postural control exercises are generally included as a part of exercise programs, during which movement practitioners can provide instructions to facilitate the performance of motor skills. Instructions can be used as cues to direct attentional focus, which has been found to affect the performance of motor skills, including balance and postural control tasks. However, no known studies to date have investigated the effect of both internal and external attentional focus instructions on static single leg balance performance, and it seems unclear whether effects of such instructions are related specifically to the direction of attention. The purpose of this study was to investigate the effect of instructing the direction of attentional focus on single leg static balance performance as reflected by the complexity of the center of pressure (COP) profile. Participants (N = 46) between the ages of 19–28 years old were randomly assigned to one of three group conditions: internal focus (INTn=15), external focus (EXTn=16) and control (CONn=15). Participants performed a thirty-five second static single leg balance task. Outcome measures were the scaling exponent determined from a detrended fluctuation analysis (DFA) to infer complexity of the COP profile in the anterior-posterior (AP) and medial-lateral (ML) directions, and root mean square error (RMSE) of the COP profile in AP and ML directions. A one-way analysis of variance (ANOVA) determined there were no statistically significant differences in the measured variables among groups. The results do not support the claim that manipulating the direction of attentional focus affects static single leg balance performance.

Understanding Balance Control in the Context of Riding a Personal Mobility Device

This study aimed at investigating the human ability to shift weight and maintain balance when driving a self-balancing personal mobility device (SPMD). In the experiment, participants performed a weight-shifting task, which is moving the center of pressure (COP) toward 15 targets comprising three distances and five directions. They were also given a maintaining balance task, which is holding the COP as close as possible to the same targets. The results showed that during the weight-shifting task, the target distance significantly increased the movement time and decreased the movement fluency and accuracy. In the balance control task, while the target distance significantly affected the postural stability, the target direction had no major effect, although there were interaction effects with the direction on the postural sway along the medial–lateral direction. It is expected that this study can help in understanding the balance control of humans and design safer SPMDs.

The Consequences of Glaucoma on Mobility and Balance Control in the Older Adults: A Cross-Sectional Study.

The aim of the study was to explore the functional impairments and related factors in older adults with moderate to advanced stages of glaucoma. Nineteen patients with glaucoma and 19 participants with no ocular disease performed step test and balance control tasks with analysis of overall stability index and fall risk index. Monocular and binocular Humphrey Visual Field tests were used to estimate visual field defect severity. The International Physical Activity Questionnaire was used to measure physical activity level. Patients with glaucoma showed poorer values for most of the mobility and balance control parameters with medium and large effect sizes (0.3-0.5). Mobility scores in patients were partly associated with their monocular visual field defect (rs = .507, p < .05). Low physical activity was identified as a risk factor for falls (rs = -.453, p < .05) and postural instability (rs = -.457, p < .05). Functional declines in dynamic tasks were not related to glaucoma severity. Older adults with glaucoma display impairment with mobility and balance control compared to controls, associated with the degree of monocular visual field loss and lower daily physical activity.

Sensory Down-Weighting in Visual-Postural Coupling Is Linked With Lower Cybersickness

Sensory dynamics can be re-shaped by environmental interaction, allowing adaptation to altered or unfamiliar conditions that would otherwise provoke challenges for the central nervous system. One such condition occurs in virtual reality, where sensory conflict is thought to induce cybersickness. Although the sensory re-weighting process is likely to underlie adaptation to cybersickness, evidence of a link between sensory re-weighting dynamics and cybersickness is rare. Here, we characterize the relationship between sensory re-weighting in a balance control task and cybersickness. Participants were exposed to visual oscillation while standing in tandem stance. The sway path length of the center of pressure (COP) was measured and averaged for each level of visual oscillation, and a ratio was computed between high and low oscillation magnitudes to reflect the relative contributions of multiple sensory sources of information concerning balance control. Results showed a significant relationship between the magnitude dependency of sway and common sub-scales of cybersickness: disorientation (r(21) = .45, p = .028) and oculomotor discomfort (r(21) = .45, p = .033). We conclude that participants who reported less cybersickness were better-able to down-weight visual information at high magnitude oscillations, thus demonstrating a lower dependency between sway and visual magnitude. The results confirm the utility of balance control as an indicator of cybersickness, and support the role of multisensory re-weighting in determining an individual’s tolerance to VR applications.

Extending the center of pressure to incorporate handhold forces: Derivation and sample application

Measures describing movement of the center of pressure (CoP) are frequently used to characterize postural control. Estimates of CoP often focus on forces that individuals exert in a single plane through the feet (standing on force plates). However, balance may also be supported by forces other than those developed at the feet, especially when walkers, handrails, and other aids are used. In these cases, it is common to neglect the contributions of handheld supports. Here, we derive and apply equations for an extended CoP that incorporates handhold forces. We then examine the influence of CoP definition (i.e., including or ignoring handhold forces) on common metrics (path length; RMS and maximum excursion; average and maximum velocity) for 12 younger adults with a handrail located lateral to the participants’ dominant hand. Participants attempted balance recovery in response to a range of small, medium and large forward and backward platform translations. Significant interactions between perturbation magnitude and CoP definition were found for most metrics. Notably, the interaction of CoP definition and perturbation magnitude significantly affected path length (p-values < 0.001). Post-hoc analyses revealed larger CoP path length when handrail forces were incorporated in CoP estimates compared to ignoring handrail forces at medium (backward: 59.9 vs. 19.0% height; forward: 70.5 vs 22.4% height) and large perturbation magnitudes (backward: 69.9 vs 22.4% height; forward: 103.5 vs 24.6% height). Incorporation of hand forces in CoP calculations can present a different view of postural balance control than relying on a feet-only CoP. This measure could be useful in assessing balance control tasks that involve the use of handrails or hand-held mobility devices.

Reduced frontopolar brain activation characterizes concussed athletes with balance deficits.

Athletes with sport-related concussions (SRC) often demonstrate deficits in postural stability. Lower cerebral blood flow in frontal cortices has been documented in athletes with symptoms after SRC, however, it is unclear if functional brain oxygenation during postural control tasks is reduced in symptomatic athletes after SRC in the same manner. We therefore compared brain oxygenation patterns in frontal cortices of symptomatic and asymptomatic athletes with SRC during postural control tasks with the hypothesis that symptomatic athletes are characterized by reduced functional brain oxygenation during postural control. 62 concussed athletes (n=31 symptomatic, n=31 asymptomatic) were investigated during four postural control tasks with eyes closed versus eyes opened conditions and stable vs. unstable surface conditions. Brain oxygenation was assessed using functional NearInfraRed Spectroscopy (fNIRS) on frontopolar cortices of each hemisphere. Postural sway was measured by the analysis of ground reaction forces. Symptomatic athletes showed greater postural sway when compared to asymptomatic athletes during postural control, particularly during closed eyes and/or unstable surface conditions. Changes of oxygenated hemoglobin (∆HbO2) within the left hemispheric frontopolar cortex were significantly reduced in symptomatic athletes when compared to asymptomatic athletes during the eyes closed condition. A stepwise linear regression analysis revealed that self-reported post-concussion symptoms such as headaches and sadness predict decreased brain oxygenation during postural control with closed eyes. Symptomatic athletes with increased postural sway are characterized by decreased frontopolar brain oxygenation during postural control tasks, particularly during conditions with closed eyes. Because the frontopolar cortex showed to be involved in redistributing executive functions to novel task situations, we conclude that athletes with post-concussion symptoms suffer from a deficit in coordinating postural adjustments to balance control tasks with reduced sensory input.

Neuroimaging of Human Balance Control: A Systematic Review.

This review examined 83 articles using neuroimaging modalities to investigate the neural correlates underlying static and dynamic human balance control, with aims to support future mobile neuroimaging research in the balance control domain. Furthermore, this review analyzed the mobility of the neuroimaging hardware and research paradigms as well as the analytical methodology to identify and remove movement artifact in the acquired brain signal. We found that the majority of static balance control tasks utilized mechanical perturbations to invoke feet-in-place responses (27 out of 38 studies), while cognitive dual-task conditions were commonly used to challenge balance in dynamic balance control tasks (20 out of 32 studies). While frequency analysis and event related potential characteristics supported enhanced brain activation during static balance control, that in dynamic balance control studies was supported by spatial and frequency analysis. Twenty-three of the 50 studies utilizing EEG utilized independent component analysis to remove movement artifacts from the acquired brain signals. Lastly, only eight studies used truly mobile neuroimaging hardware systems. This review provides evidence to support an increase in brain activation in balance control tasks, regardless of mechanical, cognitive, or sensory challenges. Furthermore, the current body of literature demonstrates the use of advanced signal processing methodologies to analyze brain activity during movement. However, the static nature of neuroimaging hardware and conventional balance control paradigms prevent full mobility and limit our knowledge of neural mechanisms underlying balance control.

Reduced Cognitive-Motor Interference on Voluntary Balance Control in Older Tai Chi Practitioners.

Recent dual-task studies suggest that Tai Chi practitioners displayed better control of standing posture and maintained a quicker response time of postural muscle activation during a stepping down activity. Whether this effect extends to voluntary balance control, specifically the limits of excursion of the center of pressure, remains to be examined. The purpose of this study was to evaluate the cognitive-motor interference pattern by examining the effects of a concurrently performed cognitive task on attention of voluntary balance control in older adults who are long-term practitioners of Tai Chi. Ten older Tai Chi practitioners and 10 age-matched nonpractitioners performed a voluntary balance task that required them to shift their weight to reach a preset target in the forward and backward directions, with (single task, ST) and without (dual task, DT) a secondary cognitive task, which was the counting backward task. The counting backward task required the individual to compute and verbalize a series of arithmetic differences between a given pair of randomly generated numbers. The cognitive task was also performed independently (cognitive-ST). All trials were performed in a random order. Balance outcomes included reaction time, movement velocity, and maximal excursion of the center of pressure provided by the NeuroCom system. Cognitive outcome was the number of correct responses generated within the 8-second trial during the ST and DT conditions. Outcome variables were analyzed using a 2-factor, group by task, analysis of variance. DT costs for the variables were calculated as the relative difference between ST and DT conditions and were compared between the 2 groups using independent t tests. Tai Chi practitioners displayed shorter reaction times (P < .001) and faster movement velocities (P < .05) of their center of pressure than older nonpractitioners for both directions; however, no difference was found between the maximal excursions of the 2 groups. Cost analyses revealed that reaction time and cognitive costs were significantly lower in the Tai Chi practitioners for both forward and backward directions (P < .05); however, similar findings for movement velocity costs were significant only in the backward direction (P < .05). Our results suggest that Tai Chi practitioners expended fewer motor and cognitive resources than older nonpractitioners during a fairly complex (dynamic) postural equilibrium task while performing a verbal working memory task. They exhibited lesser cognitive-motor interference and thus better allocation of attentional resources toward the voluntary balance control task. Given that dynamic balance is a crucial prerequisite for walking and dual-tasking ability is considered to be a significant predictor of falls in older adults, our results might point at the possible long-term benefits of Tai Chi practice to counteract age-related decline in dual-tasking ability. Findings present preliminary data for further investigation, especially related to potential benefits in fall prevention.

How providing more or less time to solve a cognitive task interferes with upright stance control; a posturographic analysis on healthy young adults

Contrasted postural effects have been reported in dual-task protocols associating balance control and cognitive task that could be explained by the nature and the relative difficulty of the cognitive task and the biomechanical significance of the force platform data. To better assess their respective role, eleven healthy young adults were required to stand upright quietly on a force platform while concomitantly solving mental-calculation or mental-navigation cognitive tasks. Various levels of difficulty were applied by adjusting the velocity rate at which the instructions were provided to the subject according to his/her maximal capacities measured beforehand. A condition without any concomitant cognitive task was added to constitute a baseline behavior. Two basic components, the horizontal center-of-gravity movements and the horizontal difference between center-of-gravity and center-of-pressures were computed from the complex center-of-pressure recorded movements. It was hypothesized that increasing the delay should infer less interaction between postural control and task solution. The results indicate that both mental-calculation and mental-navigation tasks induce reduced amplitudes for the center-of-pressure minus center-of-gravity movements, only along the mediolateral axis, whereas center-of-gravity movements were not affected, suggesting that different circuits are involved in the central nervous system to control these two movements. Moreover, increasing the delays task does not infer any effect for both movements. Since center-of-pressure minus center-of-gravity expresses the horizontal acceleration communicated to the center-of-gravity, one may assume that the control of the latter should be facilitated in dual-tasks conditions, inferring reduced center-of-gravity movements, which is not seen in our results. This lack of effect should be thus interpreted as a modification in the control of these center-of-gravity movements. Taken together, these results emphasized how undisturbed upright stance control can be impacted by mental tasks requiring attention, whatever their nature (calculation or navigation) and their relative difficulty. Depending on the provided instructions, i.e. focusing our attention on body movements or on the opposite diverting this attention toward other objectives, the evaluation of upright stance control capacities might be drastically altered.

Digital Posturography Games Correlate with Gross Motor Function in Children with Cerebral Palsy.

This pilot study aimed to assess whether performance on posturography games correlates with the Gross Motor Function Measure (GMFM) in children with cerebral palsy. Simple games using static posturography technology allowed subjects to control screen events via postural sway. Game performance was compared with GMFMs using correlation analysis in a convenience sample of nine girls and six boys with cerebral palsy. Likert scales were used to obtain subjective responses to the balance games. GMFM scores correlated with game performance, especially measures emphasizing rhythmic sway. Twelve of the 15 subjects enjoyed the game and asserted an interest in playing again. Digital posturography games engage children with cerebral palsy in balance tasks, provide visual feedback in a balance control task, and have the potential to increase autonomy in balance control training among pediatric patients with cerebral palsy. This approach can support the relationship between child and therapist. The potential for interactive posturography to complement the assessment and treatment of balance in cerebral palsy bears continuing study.

Psychometric properties of functional balance tests in children: a literature review.

Identifying balance problems are the first step towards monitoring and rehabilitation. Therefore, this paper aims to make an overview of the psychometric properties of the functional balance tests available for children. A literature search was performed in PubMED and Web of Science on 8 February 2014 and updated on 6 July 2014. A conceptual framework for functional balance tests was defined, taking balance control components and task constraints into account. The tests were selected for inclusion by consensus of 2-3 reviewers using the conceptual framework. Fourteen tests were investigated in 25 articles and analysed within the conceptual framework. The Timed Up and Go test, Pediatric Balance Scale, and Pediatric Reach Test are well investigated and all show good reliability. Validity remains unclear because of lack of a criterion standard to measure balance control. Because of the lack of good methodological studies, strong evidence for the use of one or more functional balance tests in children cannot be provided. Moreover, it is necessary that a criterion standard to measure balance is established.