Vertebral level specific modulation of paraspinal muscle activity based on vestibular signals during walking.

Evoking muscle responses by electrical vestibular stimulation (EVS) may help to understand the contribution of the vestibular system to postural control. Although paraspinal muscles play a role in postural stability, the vestibulo-muscular coupling of these muscles during walking has rarely been studied. This study aimed to investigate how vestibular signals affect paraspinal muscle activity at different vertebral levels during walking with preferred and narrow step width. Sixteen healthy participants were recruited. Participants walked on a treadmill for 8 min at 78 steps/min and 2.8 km/h, at two different step width, either with or without EVS. Bipolar electromyography was recorded bilaterally from the paraspinal muscles at eight vertebral levels from cervical to lumbar. Coherence, gain, and delay of EVS and EMG responses were determined. Significant EVS-EMG coupling (P < 0.01) was found at ipsilateral and/or contralateral heel strikes. This coupling was mirrored between left and right relative to the midline of the trunk and between the higher and lower vertebral levels, i.e. a peak occurred at ipsilateral heel strike at lower levels, whereas it occurred at contralateral heel strike at higher levels. EVS-EMG coupling only partially coincided with peak muscle activity. EVS-EMG coherence slightly, but not significantly, increased when walking with narrow steps. No significant differences were found in gain and phase between the vertebral levels or step width conditions. In summary, vertebral level specific modulation of paraspinal muscle activity based on vestibular signals might allow a fast, synchronized, and spatially co-ordinated response along the trunk during walking. KEY POINTS: Mediolateral stabilization of gait requires an estimate of the state of the body, which is affected by vestibular afference. During gait, the heavy trunk segment is controlled by phasic paraspinal muscle activity and in rodents the medial and lateral vestibulospinal tracts activate these muscles. To gain insight in vestibulospinal connections in humans and their role in gait, we recorded paraspinal surface EMG of cervical to lumbar paraspinal muscles, and characterized coherence, gain and delay between EMG and electrical vestibular stimulation, during slow walking. Vestibular stimulation caused phasic, vertebral level specific modulation of paraspinal muscle activity at delays of around 40 ms, which was mirrored between left, lower and right, upper vertebral levels. Our results indicate that vestibular afference causes fast, synchronized, and spatially co-ordinated responses of the paraspinal muscles along the trunk, that simultaneously contribute to stabilizing the centre of mass trajectory and to keeping the head upright.

Impact of visual rotations on heading direction and center of mass control during steady-state gait.

Visual information is essential to navigate the environment and maintain postural stability during gait. Visual field rotations alter the perceived heading direction, resulting in gait trajectory deviations, known as visual coupling. It is unclear how center of mass (CoM) control relative to a continuously changing base of support (BoS) is adapted to facilitate visual coupling. This study aimed to characterize mediolateral (ML) balance control during visual coupling in steady-state gait. Sixteen healthy participants walked on an instrumented treadmill, naive to sinusoidal low-frequency (0.1 Hz) rotations of the virtual environment around the vertical axis. Rotations were continuous with 1) high or 2) low amplitude or were 3) periodic with 10-s intervals. Visual coupling was characterized with cross-correlations between CoM trajectory and visual rotations. Balance control was characterized with the ML margin of stability (MoSML) and by quantifying foot placement control as the relation between CoM dynamics and lateral foot placement. Visual coupling was strong on a group level (continuous low: 0.88, continuous high: 0.91, periodic: 0.95) and moderate to strong on an individual level. Higher rotation amplitudes induced stronger gait trajectory deviations. The MoSML decreased toward the deviation direction and increased at the opposite side. Foot placement control was similar compared with regular gait. Furthermore, pelvis and foot reorientation toward the rotation direction was observed. We concluded that visual coupling was facilitated by reorientating the body and shifting the extrapolated CoMML closer to the lateral BoS boundary toward the adjusted heading direction while preserving CoM excursion and foot placement control.NEW & NOTEWORTHY Healthy, naive participants were unaware of subtle, low-frequency rotations of the visual field but still coupled their gait trajectory to a rotating virtual environment. In response, participants decreased their margin of stability toward the new heading direction, without changing the center of mass excursion magnitude and foot placement strategy.

Balance Control in Individuals with Hearing Impairment: A Systematic Review and Meta-Analysis.

Comprehensive insights into balance control of individuals with hearing impairment are compared with individuals with hearing. Primary sources were obtained from 7 databases including PubMed, LILACS, SCOPUS, CINAHL, PEDro, CENTRAL, and Web of Science. The search period extended from inception until January 5, 2022. The systematic review included 24 studies and 27 trials, with a total of 2,148 participants. The meta-analysis showed a significant difference in the average balance control between individuals with hearing impairment and individuals with hearing, with individuals with hearing having a favorable advantage (p = 0.001). Additionally, average balance control was found to be in favor of individuals with hearing (p = 0.001) when comparing individuals with hearing impairment who participated in sports. Finally, individuals with hearing impairment who participated in sports demonstrated a significantly higher average difference in balance control (p = 0.001) when compared to sedentary people with hearing impairment. Our meta-analysis results indicate a balance defect in individuals with hearing impairment compared to individuals with hearing. In addition, with increasing age, the balance in individuals with hearing impairment improved. Additionally, the dependence of individuals with hearing impairment on the visual and proprioception systems to maintain balance increased. Finally, there was more dependence on the proprioception than the visual system, while individuals with hearing had stronger average balance control than individuals with hearing impairment who participated in sports, when compared to sedentary people with hearing impairment.

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

OBJECTIVES: To 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. DESIGN: Cross-sectional study. SETTINGS: Sports Rehabilitation Laboratory. PARTICIPANTS: Eighty-eight recreational athletes (47 CAI and 41 healthy control) were recruited. INTERVENTIONS: No applicable. MAIN OUTCOME MEASURES: Balance 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. RESULTS: Athletes 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). CONCLUSIONS: Athletes 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.

The psychometric properties of the Six-Spot Step Test - a systematic review using the COSMIN guidelines.

OBJECTIVE: Accurate and reliable balance measures are important for prescribing fall prevention treatments and monitoring their effectiveness. Thus, we aimed to systematically review the psychometric properties of the Six-Spot Step Test, an increasingly used measure of dynamic balance. DATA SOURCES: A literature search using the free-text term "Six-Spot Step Test" was performed on 12 February 2024, in Medline, Embase, Rehabilitation & Sports Medicine and SPORTDiscus. Eligibility criteria were adults aged 18 or more, trials evaluating the psychometric properties of the Six-Spot Step Test, and English-language articles. Conference abstracts were excluded. REVIEW METHODS: Two investigators screened and selected data independently and assessed the methodological quality and evidence using the COSMIN Risk of Bias checklist and modified GRADE approach. One investigator extracted study characteristics such as design, population and psychometric properties. RESULTS: Of the 159 articles identified, 16, evaluating multiple measurement properties, were included in the final analysis. A total of 1319 people participated, including people affected by Stroke, multiple sclerosis, Parkison's disease, chronic inflammatory polyneuropathy and older adults with balance problems. Eight articles assessing reliability (n = 618, intraclass correlations coefficient ≥0.7, minimal detectable change = 22%) and 12 construct validity (n = 1082, 83% true hypothesis, area under the curve >0.7) exhibited sufficient methodological quality with high-level evidence, while two studies (n = 167) examining responsiveness showed very low evidence. CONCLUSION: Apart from responsiveness, robust evidence supports the reliability and validity of the Six-Spot Step Test for assessing dynamic balance in a specific group of individuals with neurological diseases and older adults. Further, it is considered feasible for clinical use.

Exploring the effect of human-drone communication modality on safety and balance control in virtual construction environments.

This study examines the impact of Human-Drone Interaction (HDI) modalities on construction workers' safety and balance control within virtual environments. Utilising virtual reality (VR) simulations, the study explored how gesture and speech-based communications influence workers' physical postures and balance, contrasting these modalities with a non-interactive control group. One hundred participants were recruited, and their movements and balance control were tracked using motion sensors while they interacted with virtual drones through either gesture, speech, or without communication. Results showed that interactive modalities significantly improved balance control and reduced the risk of falls, suggesting that advanced HDI can enhance safety on construction sites. However, speech-based interaction increased cognitive workload, highlighting a trade-off between physical safety and mental strain. These findings underscore the potential of integrating intuitive communication methods into construction operations, although further research is needed to optimise these interactions for long-term use and in diverse noise environments.

This study examines the impact of Human-Drone Interaction (HDI) modalities on construction workers' safety and balance control within virtual environments with a human subject experiment. Results showed that interactive modalities significantly improved balance control and reduced the risk of falls.

Tai Chi counteracts age-related somatosensation and postural control declines among older adults.

Objective: To investigate the effect of a 16-week Tai Chi practice on strength, tactile sensation, kinesthesia, and static postural control among older adults of different age groups. Methods: This is a quasi-experimental study. Thirteen participants aged 60-69 years (60-69yr), 11 aged 70-79 years (70-79yr), and 13 aged 80-89 years (80-89yr) completed 16 weeks of 24-form Tai Chi practice. Their ankle and hip peak torque, tactile sensation, ankle and knee kinesthesia, and the root mean square of the center of pressure (Cop-RMS) were measured before (week 0) and after (week 17) practice. Results: 80-89yr showed less ankle plantar/dorsiflexion and hip abduction peak torques (p = 0.003, p < 0.001, p = 0.001), and a greater ankle plantar/dorsiflexion kinesthesia (p < 0.001, p = 0.002) than 60-69yr and 70-79yr. Greater ankle plantar/dorsiflexion and hip abduction torques (p = 0.011, p < 0.001, p = 0.045), improved arch and heel tactile sensation (p = 0.040, p = 0.009), and lower knee flexion/extension kinesthesia (p < 0.001, p = 0.044) were observed at week 17. The significant group*practice interaction for the fifth metatarsal head tactile sensation (p = 0.027), ankle plantar/dorsiflexion kinesthesia (p < 0.001, p = 0.004), and the CoP-RMS in the mediolateral direction (p = 0.047) only in 80-89yr revealed greater improvement at week 17. Conclusion: Tai Chi practice increased strength, tactile sensation, kinesthesia, and static postural control among older adults. Tai Chi practice improved tactile, kinesthesia sensations, and static postural control among older adults over 80, who presented with worse strength and kinesthesia than their younger counterparts. Tai Chi practice offers a safe exercise option for those aged over 80 to encourage improvements in sensorimotor control.

The role of torque feedback in standing balance.

It has been proposed that sensory force/pressure cues are integrated within a positive feedback mechanism, which accounts for the slow dynamics of human standing behavior and helps align the body with gravity. However, experimental evidence of this mechanism remains scarce. This study tested predictions of a positive torque feedback mechanism for standing balance, specifically that differences between a "reference" torque and actual torque are self-amplified, causing the system to generate additional torque. Seventeen healthy young adults were positioned in an apparatus that permitted normal sway at the ankle until a brake on the apparatus was applied, discreetly "locking" body movement during stance. Once locked, a platform positioned under the apparatus remained in place (0 mm) or slowly translated backward (3 mm or 6 mm), tilting subjects forward. Postural behavior was characterized by two distinct responses: the center of pressure (COP) offset (i.e., change in COP elicited by the surface translation) and the COP drift (i.e., change in COP during the sustained tilt). Model simulations were performed using a linear balance control model containing torque feedback to provide a conceptual basis for the interpretation of experimental results. Holding the body in sustained tilt positions resulted in COP drifting behavior, reflecting attempts of the balance control system to restore an upright position through increases in plantar flexor torque. In line with predictions of positive torque feedback, larger COP offsets led to faster increases in COP over time. These findings provide experimental support for a positive torque feedback mechanism involved in the control of standing balance.NEW & NOTEWORTHY Using model simulations and a novel experimental approach, we tested behavioral predictions of a sensory torque feedback mechanism involved in the control of upright standing. Torque feedback is thought to reduce the effort required to stand and play a functional role in slowly aligning the body with gravity. Our results provide experimental evidence of a torque feedback mechanism and offer new and valuable insights into the sensorimotor control of human balance.

Perturbation-based balance training leads to improved reactive postural responses in individuals with Parkinson's disease and freezing of gait.

Perturbation-based balance training (PBT) exposes individuals to a series of sudden upright balance perturbations to improve their reactive postural responses. In this study, we aimed to evaluate the effect of a short PBT program on body balance recovery following a perturbation in individuals with freezing of gait due to Parkinson's disease. Volunteers (mean age = 64 years, SD = 10.6) were pseudorandomly assigned either to a PBT (n = 9) or to a resistance training (RT, n = 10) group. PBT was implemented through balance perturbations varying in the kind, direction, side and magnitude of support base displacements. Both groups exercised with progressive difficulty/load activities twice a week for 4 weeks. Specific gains and generalization to dual-tasking and faster-than-trained support base displacements were evaluated 24 h after the end of the training, and retention was evaluated after 30 days of no training. Results showed that, compared with RT, PBT led to more stable postural responses in the 30-day retention evaluation, as indicated by decreased CoP displacement, velocity and time to direction reversal and reduced numbers of near-falls. We found no transfer either to a dual task or to a higher perturbation velocity. In conclusion, a training program based on diverse unpredictable balance perturbations improved the stability of reactive postural responses to those perturbations suffered during the training, without generalization to more challenging tasks.

Turning and multitask gait unmask gait disturbance in mild-to-moderate multiple sclerosis: Underlying specific cortical thinning and connecting fibers damage.

Multiple sclerosis (MS) causes gait and cognitive impairments that are partially normalized by compensatory mechanisms. We aimed to identify the gait tasks that unmask gait disturbance and the underlying neural correlates in MS. We included 25 patients with MS (Expanded Disability Status Scale score: median 2.0, interquartile range 1.0-2.5) and 19 healthy controls. Fast-paced gait examinations with inertial measurement units were conducted, including straight or circular walking with or without cognitive/motor tasks, and the timed up and go test (TUG). Receiver operating characteristic curve analysis was performed to distinguish both groups by the gait parameters. The correlation between gait parameters and cortical thickness or fractional anisotropy values was examined by using three-dimensional T1-weighted imaging and diffusion tensor imaging, respectively (corrected p < .05). Total TUG duration (>6.0 s, sensitivity 88.0%, specificity 84.2%) and stride velocity during cognitive dual-task circular walking (<1.12 m/s, 84.0%, 84.2%) had the highest discriminative power of the two groups. Deterioration of these gait parameters was correlated with thinner cortical thickness in regional areas, including the left precuneus and left temporoparietal junction, overlapped with parts of the default mode network, ventral attention network, and frontoparietal network. Total TUG duration was negatively correlated with fractional anisotropy values in the deep cerebral white matter areas. Turning and multitask gait may be optimal to unveil partially compensated gait disturbance in patients with mild-to-moderate MS through dynamic balance control and multitask processing, based on the structural damage in functional networks.

Correlation of balance posturographic parameters during quiet standing with the berg balance scale in patients with parkinson's disease.

BACKGROUND: Parkinson's disease (PD) is often clinically associated with posture instability and more easily falling. The Berg balance scale is a clinical indicator commonly used to subjectively evaluate a patient's balance ability. Meanwhile, computerized force platforms have been used in research on postural control. The various parameters obtained from posturography are interpreted to assess balance ability. The present study aims to explore the correlations between posturographic variables and the BBS, and furthermore to efficiently evaluate postural instability and fall risk of early and moderate PD patients. METHODS: A total of 46 PD patients were involved in the experiment. Patients were asked to perform BBS tests and force platform tests under eye open (EO) and eye closed (EC) conditions. The recorded COP signal was analyzed with the time domain statistical method, the frequency domain method of Power Spectral Density (PSD), and structural methods of Stabilogram Diffusion Analysis (SDA), Sway Density Plot (SDP) to retrieve different posturographic variables. The correlation between posturographic variables under EO and EC conditions with BBS was compared statistically. The significantly correlated posturographic parameters were then applied to analyze posturographic differences between different groups: faller vs. non-faller (patients with/without a history of falls in the past 12 months). RESULTS: Among the different posturographic parameters, the prediction ellipse area, the slope of the regression line at a high-frequency band of PSD in the medial-lateral (ML) direction, the crossover point of the regression lines of SDA in the anterior-posterior (AP) direction, and the distance between successive peaks of SDP had significant correlations with BBS. These selected BBS-related parameters also showed significant differences between faller and non-faller. The selected posturographic parameters can be used as effective indicators to evaluate the balance ability of Parkinson's disease patients.

Identifying priorities for balance interventions through a participatory co-design approach with end-users.

BACKGROUND: Most individuals living with spinal cord injuries/diseases (SCI/D) or stroke experience at least one fall each year; hence, the development of interventions and technologies that target balance control is needed. The purpose of this study was to identify and explore the priorities for balance-focused interventions and technologies from the perspectives of end-users to assist with the design of an intervention that combines functional electrical stimulation (FES) with visual feedback training for standing balance. METHODS: Two individuals with SCI/D, one individual with stroke, two physical therapists (PT) and one hospital administrator were recruited. Participants attended three focus group meetings that followed a participatory co-design approach. A semi-structured interview guide, developed from the FAME (Feasibility, Appropriateness, Meaningfulness, Effectiveness, Economic Evidence) framework, was used to lead the discussion, querying participants' experiences with balance deficits and interventions, and FES. Meetings were audio-recorded and transcribed verbatim. An iterative and reflexive inductive thematic analysis was applied to the transcripts by three researchers. RESULTS: Four themes were identified: (1) Balance is meaningful for daily life and rehabilitation. Participants acknowledged various factors influencing balance control and how balance deficits interfered with participation in activities. End-users stressed the importance of continuing to work on one's balance after discharge from hospital-based rehabilitation. (2) Desired characteristics of balance interventions. Participants explained that balance interventions should be tailored to an individual's unique needs and goals, relevant to their lives, balance their safety and risk, and be engaging. (3) Prior experiences with FES to inform future therapeutic use. Participants with stroke or SCI/D described initial apprehension with FES, but experienced numerous benefits that motivated them to continue with FES. Challenges with FES were mentioned, including wires, cost, and time of set up. (4) Potential role of FES in balance interventions. Participants felt that FES would complement balance interventions; however, they had not experienced this combination of therapies previously. CONCLUSIONS: End-users described how their experiences with balance deficits, rehabilitation, and FES informed their priorities for balance interventions. The findings inform the design and implementation of future balance interventions for individuals with SCI/D or stroke, including an intervention involving FES and visual feedback training.

The feasibility of using an auditory cue to elicit anticipatory postural adjustments for a posterior perturbation.

When humans are exposed to a predictable external perturbation, they usually generate anticipatory postural adjustments (APAs), which reduce the effect of potential body disturbance. However, when an external perturbation comes from behind and as such unpredicted, no APAs are generated, which challenges postural control. The aim of this study was to examine whether humans exposed to unpredictable perturbations could generate APAs using an auditory cue. Ten young adults were exposed to external perturbations hitting their shoulders from behind with or without an auditory cue prior to the physical impact. Electromyography (EMG) activities of eight trunk and leg muscles and center-of-pressure (COP) displacements were recorded and analyzed during the anticipatory and compensatory phases of postural control. Outcome measures included the latencies and integrals of muscle activities, COP displacements, and indices of co-contraction and reciprocal activation of muscles. The results showed that young adults were able to rely on an auditory cue to generate APAs prior to external perturbations coming from behind, and they demonstrated stronger APAs with training. Moreover, they utilized co-contraction of ventral and dorsal muscles as their APA response. The outcome provides a foundation for future studies aiming at using auditory cues to facilitate the generation of APAs and improve postural control in people with impaired balance while exposed to perturbations.

Age-related effects of repeated task switching in a novel voluntary gait adaptability task.

Age-related effects of task switching have been extensively studied based on cognitive tasks and simple motor tasks, but less on complex cognitive-motor tasks involving dynamic balance control while walking. The latter tasks may especially be difficult and relevant for older adults in terms of safe mobility in daily life. The aim of the present study was, therefore, to examine age-related changes in task-switching adaptability using a novel voluntary gait adaptability test protocol. Fifteen healthy young (27.5 ± 2.9 years) and 16 healthy old (70.9 ± 7.6 years) adults carried out 2 different visual target stepping tasks (either target avoidance or stepping) twice in a block (A-B-A-B, 2 min per task; three blocks in total) without any intrablock breaks. Our results showed that old adults showed significantly more step errors both in Tasks A and B as well as more interference effects than young adults. Age-related differences in step accuracy were significant in the anterior-posterior direction both in Task A and B but not in the mediolateral direction. Both in step errors and accuracy, no interaction effects of age and trial were shown. Our results suggest that old adults could not cope with rapid and direct task changes in our voluntary gait adaptability task as young adults. Since the significant main effect of trial for Task B, but not Task A appears to be due to different task complexity, further studies may determine the effect of task complexity or task switch timing.

Arterial stiffness and augmentation index are associated with balance function in young adults.

OBJECTIVE: Arterial stiffness and pulsatile central hemodynamics have been shown to affect various aspects of physical function, such as exercise capacity, gait speed, and motor control. The aim of this study was to examine the potential association between arterial stiffness and balance function in healthy younger men and women. METHODS: 112 participants (age = 21 ± 4 years, n = 78 women) underwent measures of arterial stiffness, pulsatile central hemodynamics, balance function and physical fitness in this cross-sectional study. Postural sway was measured in triplicate while participants stood on a foam surface with their eyes closed for 20 s. The average total center of pressure path length from the three trials was used for analysis. Measures of vascular function were estimated using an oscillometric blood pressure device while at rest and included pulse wave velocity (PWV), augmentation index (AIx), and pulse pressure amplification. Measures of physical fitness used as covariates in statistical models included handgrip strength determined from a handgrip dynamometer, lower-body flexibility assessed using a sit-and-reach test, estimated maximal aerobic capacity (VO2max) using heart rate and a step test, and body fat percentage measured from air displacement plethysmography. RESULTS: The results from linear regression indicated that after considering sex, mean arterial pressure, body fat, estimated VO2max, handgrip strength, and sit-and-reach, PWV (ß = 0.44, p < 0.05) and AIx (ß = - 0.25, p < 0.01) were significant predictors of postural sway, explaining 10.2% of the variance. CONCLUSION: Vascular function is associated with balance function in young adults independent of physical fitness. Increased arterial stiffness may negatively influence balance, while wave reflections may be protective for balance.

The effect of foot posture on static balance, ankle and knee proprioception in 18-to-25-year-old female student: a cross-sectional study.

BACKGROUND & PURPOSE: Afferent input from the sole affects postural stability. Cutaneous reflexes from the foot are important to posture and gait. Lower-limb afferents alone provide enough information to maintain upright stance and are critical in perceiving postural sway. Altered feedback from propreoceptive receptors alters gait and patterns of muscle activation. The position and posture of the foot and ankle may also play an important role in proprioceptive input.Therefore, the current research aims to compare static balance and ankle and knee proprioception in people with and without flexible flatfeet. METHODOLOGY: 91 female students between the ages of 18 and 25 voluntarily participated in this study, of which 24 were in the flexible flatfoot group and 67 were in the regular foot group after evaluating the longitudinal arch of the foot. The position sense of ankle and knee joints were measured using the active reconstruction test of the ankle and knee angle; Static balance was measured using the Sharpened Romberg test. Data were non-normally distributed. Accordingly, non-parametric tests were applied. The Kruskal-Wallis test was applied to compare differences between groups in variables. RESULT: Kruskal-Wallis test showed a significant difference between two groups of flat feet and normal feet in the variables of static balance and position sense of ankle plantarflexion, ankle dorsiflexion, and knee flexion (p ≤ 0.05). A significant correlation was found between static balance and sense of ankle and knee position in the group with normal feet. The analysis of the regression line also showed that ankle and knee position sense could predict the static balance score in the regular foot group (ankle dorsiflexion position sense 17% (R2 = 0.17), ankle plantarflexion position sense 17% (R2 = 0.17) and knee flexion position sense 46% (R2 = 0.46) explain of changes in static balance). DISCUSSION & CONCLUSION: Flexible flatfoot soles can cause loss of balance and sense of joint position; therefore, according to this preliminary study, clinicians must be aware and should take into account this possible deficit in the management of these patients.

Anticipatory postural adjustments and kinematic analysis of step ascent and descent in adults with Down syndrome.

BACKGROUND: Step ascent and descent is one of the most common daily tasks. Although it is generally considered a rather simple movement, it may not be so easy for participants with Down syndrome. METHODS: A kinematic analysis of step ascent and descent was conducted, and a comparison between 11 adult participants with Down syndrome and 23 healthy participants was carried out. This analysis was accompanied by a posturographic analysis with the aim of evaluating aspects relating to balance. The principal aim of postural control was to investigate the trajectory of the centre of pressure, while the kinematic analysis of movement included the following: (1) the analysis of anticipatory postural adjustments, (2) the calculation of spatiotemporal parameters and (3) the evaluation of articular range of motion. RESULTS: A general instability for participants with Down syndrome, highlighted in the postural control by an increased anteroposterior and mediolateral excursion, when the test was conducted with both open and closed eyes, was found out. Regarding anticipatory postural adjustments, this deficit in balance control was revealed by the execution of small steps before completing the movement and by a much longer preparation time anticipating the movement. In addition, the kinematic analysis reported a longer ascent and descent time and a lower velocity, accompanied by a greater rising of both limbs in ascent, which indicates an increased perception of the obstacle. Finally, a wider trunk range of motion in both the sagittal and frontal planes was revealed. CONCLUSIONS: All the data confirm a compromised balance control that could be associated with damage to the sensorimotor centre.

Assisting walking balance using a bio-inspired exoskeleton controller.

BACKGROUND: Balance control is important for mobility, yet exoskeleton research has mainly focused on improving metabolic energy efficiency. Here we present a biomimetic exoskeleton controller that supports walking balance and reduces muscle activity. METHODS: Humans restore balance after a perturbation by adjusting activity of the muscles actuating the ankle in proportion to deviations from steady-state center of mass kinematics. We designed a controller that mimics the neural control of steady-state walking and the balance recovery responses to perturbations. This controller uses both feedback from ankle kinematics in accordance with an existing model and feedback from the center of mass velocity. Control parameters were estimated by fitting the experimental relation between kinematics and ankle moments observed in humans that were walking while being perturbed by push and pull perturbations. This identified model was implemented on a bilateral ankle exoskeleton. RESULTS: Across twelve subjects, exoskeleton support reduced calf muscle activity in steady-state walking by 19% with respect to a minimal impedance controller (p < 0.001). Proportional feedback of the center of mass velocity improved balance support after perturbation. Muscle activity is reduced in response to push and pull perturbations by 10% (p = 0.006) and 16% (p < 0.001) and center of mass deviations by 9% (p = 0.026) and 18% (p = 0.002) with respect to the same controller without center of mass feedback. CONCLUSION: Our control approach implemented on bilateral ankle exoskeletons can thus effectively support steady-state walking and balance control and therefore has the potential to improve mobility in balance-impaired individuals.

Recurrent Neural Network Methods for Extracting Dynamic Balance Variables during Gait from a Single Inertial Measurement Unit.

Monitoring dynamic balance during gait is critical for fall prevention in the elderly. The current study aimed to develop recurrent neural network models for extracting balance variables from a single inertial measurement unit (IMU) placed on the sacrum during walking. Thirteen healthy young and thirteen healthy older adults wore the IMU during walking and the ground truth of the inclination angles (IA) of the center of pressure to the center of mass vector and their rates of changes (RCIA) were measured simultaneously. The IA, RCIA, and IMU data were used to train four models (uni-LSTM, bi-LSTM, uni-GRU, and bi-GRU), with 10% of the data reserved to evaluate the model errors in terms of the root-mean-squared errors (RMSEs) and percentage relative RMSEs (rRMSEs). Independent t-tests were used for between-group comparisons. The sensitivity, specificity, and Pearson's r for the effect sizes between the model-predicted data and experimental ground truth were also obtained. The bi-GRU with the weighted MSE model was found to have the highest prediction accuracy, computational efficiency, and the best ability in identifying statistical between-group differences when compared with the ground truth, which would be the best choice for the prolonged real-life monitoring of gait balance for fall risk management in the elderly.

Daily Outdoor Cycling by Older Adults Preserves Reactive Balance Behavior: A Case-Control Study.

We examined whether older adults who cycle outdoors regularly have better reactive balance control than noncycling older adults. Sixteen cyclist older adults and 24 age-, sex-, and health-matched controls who did not cycle (noncyclists) were exposed to unannounced perturbations of increased magnitudes in standing. We evaluated the strategies and kinematics employed at each perturbation magnitude. We found that cyclists exhibited a significantly higher stepping threshold, lower probability of stepping at each perturbation magnitude, and lower number of trials in which the participant needed to make a step to retain their balance. Cyclists also tended to recover balance using unloaded leg strategies in the first recovery step rather than a loaded leg strategy; they showed faster swing phase duration in the first recovery step, better controlling the displacement of center of mass than noncyclists. Older adults who cycle regularly outdoors preserve their reactive balance functions, which may reduce fall risks.