Postural control in healthy adults: Determinants of trunk sway assessed with a chest-worn accelerometer in 12 quiet standing tasks

Validation of the Equidyn protocol for evaluation of dynamic balance in older adults through a smartphone application

BACKGROUND

Different tasks and proxy measurements have been employed to evaluate dynamic balance in older individuals. However, due to inherent limitations, results from most evaluations could hardly be taken as valid measurements of dynamic balance.

RESEARCH QUESTION

Is the Equidyn smartphone application-based protocol valid and sensitive for assessment of dynamic balance in older adults?

METHODS

Dynamic balance was evaluated in 52 physically active individuals, age range 60-80 years (M = 69.36). The dynamic tasks were one-leg sway either in the mediolateral (ML) or anteroposterior (AP) direction while supported on the contralateral leg, and cyclic sit-to-stand with a narrow support base. These tasks were performed under standardized movement amplitude and rhythm. Outcomes were correlated with unipedal quiet standing. A smartphone was attached to the trunk backside, and a custom-made application (Equidyn) was employed to provide guidance throughout evaluation, timed beeps to pace the movements, and three-dimensional trunk acceleration measurement for balance evaluation.

RESULTS

Our data showed (a) that both ML and AP leg sway tasks were sensitive to aging and to direction of leg sway movements; (b) referenced to quiet unipedal stance, moderate/strong correlations for the ML/AP leg sway tasks and moderate correlations for the sit-to-stand task; and (c) moderate/strong correlations between the ML and AP leg sway tasks, and moderate correlations between the sit-to-stand and the two unipedal dynamic tasks in the ML acceleration direction.

SIGNIFICANCE

The current results support the conclusion that the Equidyn protocol is a sensitive and valid tool to evaluate dynamic balance in healthy older individuals. The protocol tasks standardized in amplitude and rhythm favor their reproducibility and trunk acceleration data interpretation. As the whole assessment is made through a smartphone application, this dynamic balance evaluation could be made in a low-cost simple way both in the laboratory and clinical settings.

Symmetric unipedal balance in quiet stance and dynamic tasks in older individuals

Previous evidence of increased difference of muscular strength between the dominant and non-dominant legs in older adults suggests the possibility of dissimilar balance control between the legs (between-leg asymmetry) associated with aging. In the current investigation, we evaluated between-leg asymmetries in older adults when performing quiet and dynamic balance tasks. Fifty-two physically active and healthy older adults within the age range of 60 to 80 years were recruited. Participants performed balance tasks in unipedal stance, including quiet standing and cyclic sway (rhythmic oscillation) of the non-supporting leg in the anteroposterior or mediolateral directions, producing foot displacements with amplitudes of 20 cm paced in 1 Hz through a metronome. Body balance was evaluated through trunk accelerometry, by using the sensors embedded into a smartphone fixed at the height of the 10th-12th thoracic spines. Analysis revealed lack of significant differences in balance control between the legs either when comparing the right versus left or the preferred versus non-preferred legs, regardless of whether they were performing quiet stance or dynamic tasks. Further examination of the data showed high between-leg correlation coefficients (rs range: 0.71-0.84) across all tasks. Then, our results indicated symmetric and associated between-leg balance control in the examined older adults.

Sensory integration and segmental control of posture during pregnancy

BACKGROUND

Approximately 25% of pregnant people fall, yet the underlying mechanisms of this increased fall-risk remain unclear. Prior studies examining pregnancy and balance have utilized center of pressure analyses and reported mixed results. The purpose of this study was to examine sensory and segmental contributions to postural control throughout pregnancy using accelerometer-based measures of sway.

METHODS

Thirty pregnant people (first trimester: n = 10, second trimester: n = 10, third trimester: n = 10) and 10 healthy, nonpregnant control people stood quietly for one minute in four conditions: eyes open on a firm surface, eyes closed on a firm surface, eyes open on a foam pad, and eyes closed on foam. Postural sway was quantified using the root mean square accelerations in the anterior-posterior and medial-lateral directions from an inertial sensor at the lumbar region. Sensory sway ratios, segmental coherence and co-phase, were calculated to assess sensory contributions and segmental control, respectively.

FINDINGS

Pregnant people did not display greater sway compared to healthy, nonpregnant controls. There were no group differences in vestibular, visual, or somatosensory sway ratios, and no significant differences in balance control strategies between pregnant and nonpregnant participants across sensory conditions.

INTERPRETATION

The small effects observed here contrast prior studies and suggest larger, definitive studies are needed to assess the effect of pregnancy on postural control. This study serves as a preliminary exploration of pregnant sensory and segmental postural control and highlights the need for future to hone the role of balance in fall risk during pregnancy.

Relationship between Timed Up and Go performance and quantitative biomechanical measures of balance

Traumatic brain injury (TBI) impairs sensory-motor functions, with debilitating consequences on postural control and balance, which persist during the chronic stages of recovery. The Timed Up and Go (TUG) test is a reliable, safe, time-efficient, and one of the most widely used clinical measures to assess gait, balance, and fall risk in TBI patients and is extensively used in inpatient and outpatient settings. Although the TUG test has been used extensively due to its ease of performance and excellent reliability, limited research has been published that investigates the relationship between TUG performance and quantitative biomechanical measures of balance. The objective of this paper was to quantify the relationship between biomechanical variables of balance and the TUG scores in individuals with chronic TBI. Regression models were constructed using six biomechanical variables to predict TUG scores. The model that conservatively removed gait speed (i.e., TUG-1/GS) gave the best results, achieving a root-mean-square error of ∼±2 s and explaining over 69% of the variability.

Gait quality in prosthesis users is reflected by force-based metrics when learning to walk on a new research-grade powered prosthesis

Introduction

Powered prosthetic feet require customized tuning to ensure comfort and long-term success for the user, but tuning in both clinical and research settings is subjective, time intensive, and the standard for tuning can vary depending on the patient's and the prosthetist's experience levels.

Methods

Therefore, we studied eight different metrics of gait quality associated with use of a research-grade powered prosthetic foot in seven individuals with transtibial amputation during treadmill walking. We compared clinically tuned and untuned conditions with the goal of identifying performance-based metrics capable of distinguishing between good (as determined by a clinician) from poor gait quality.

Results

Differences between the tuned and untuned conditions were reflected in ankle power, both the vertical and anterior-posterior impulse symmetry indices, limb-force alignment, and positive ankle work, with improvements seen in all metrics during use of the tuned prosthesis.

Discussion

Notably, all of these metrics relate to the timing of force generation during walking which is information not directly accessible to a prosthetist during a typical tuning process. This work indicates that relevant, real-time biomechanical data provided to the prosthetist through the future provision of wearable sensors may enhance and improve future clinical tuning procedures associated with powered prostheses as well as their long-term outcomes.

Effect of test duration and sensor location on the reliability of standing balance parameters derived using body-mounted accelerometers

BACKGROUND

Balance parameters derived from wearable sensor measurements during postural sway have been shown to be sensitive to experimental variables such as test duration, sensor number, and sensor location that influence the magnitude and frequency-related properties of measured center-of-mass (COM) and center-of-pressure (COP) excursions. In this study, we investigated the effects of test duration, the number of sensors, and sensor location on the reliability of standing balance parameters derived using body-mounted accelerometers.

METHODS

Twelve volunteers without any prior history of balance disorders were enrolled in the study. They were asked to perform two 2-min quiet standing tests with two different testing conditions (eyes open and eyes closed). Five inertial measurement units (IMUs) were employed to capture postural sway data from each participant. IMUs were attached to the participants' right legs, the second sacral vertebra, sternum, and the left mastoid processes. Balance parameters of interest were calculated for the single head, sternum, and sacrum accelerometers, as well as, a three-sensor combination (leg, sacrum, and sternum). Accelerometer data were used to estimate COP-based and COM-based balance parameters during quiet standing. To examine the effect of test duration and sensor location, each 120-s recording from different sensor locations was segmented into 20-, 30-, 40-, 50-, 60-, 70-, 80-, 90-, 100-, and 110-s intervals. For each of these time intervals, time- and frequency-domain balance parameters were calculated for all sensor locations.

RESULTS

Most COM-based and COP-based balance parameters could be derived reliably for clinical applications (Intraclass-Correlation Coefficient, ICC ≥ 0.90) with a minimum test duration of 70 and 110 s, respectively. The exceptions were COP-based parameters obtained using a sacrum-mounted sensor, especially in the eyes-closed condition, which could not be reliably used for clinical applications even with a 120-s test duration.

CONCLUSIONS

Most standing balance parameters can be reliably measured using a single head- or sternum-mounted sensor within a 120-s test duration. For other sensor locations, the minimum test duration may be longer and may depend on the specific test conditions.

Accelerometry applications and methods to assess standing balance in older adults and mobility-limited patient populations: a narrative review

Accelerometers provide an opportunity to expand standing balance assessments outside of the laboratory. The purpose of this narrative review is to show that accelerometers are accurate, objective, and accessible tools for balance assessment. Accelerometry has been validated against current gold standard technology, such as optical motion capture systems and force plates. Many studies have been conducted to show how accelerometers can be useful for clinical examinations. Recent studies have begun to apply classification algorithms to accelerometry balance measures to discriminate populations at risk for falls. In addition to healthy older adults, accelerometry can monitor balance in patient populations such as Parkinson's disease, multiple sclerosis, and traumatic brain injury. The lack of software packages or easy-to-use applications have hindered the shift into the clinical space. Lack of consensus on outcome metrics has also slowed the clinical adoption of accelerometer-based balance assessments. Future studies should focus on metrics that are most helpful to evaluate balance in specific populations and protocols that are clinically efficacious.

Physical activity and sport practice to improve balance control of visually impaired individuals: a narrative review with future perspectives

Visual disability negatively impacts balance, everyday self-efficacy, and mobility and often leads affected subjects to perceive physical exercise as a burdensome challenge thus discouraging them from practicing. Despite the well-proven benefits of regular physical activity in visually impaired people, especially addressing postural control, there are no specific guidelines and most of the available literature seems to be flawed by critical issues. Given the wide heterogeneity and the multidimensional needs of this population, a more realistic and target-specific perspective is needed in order to properly investigate and promote exercise practice and adherence for balance improvement. On this basis, through a critical overview of the recent literature, the present article aimed to enrich the current knowledge about this topic by providing innovative suggestions, both practical and methodological, and specifically deepening the disability-related deficits and peculiarities of different age ranges. Moreover, since a multidisciplinary approach is advisable when designing and leading exercise protocols tailored to visually impaired individuals, such innovative hints also highlighted the central role of the adapted physical activity specialist, hence contributing to foster its official professional recognition and involvement in this field.

Modalities of sequential human robot collaboration trigger different modifications of trunk oscillations

Introduction

Human robot collaboration is quickly gaining importance in the robotics and ergonomics fields due to its ability to reduce biomechanical risk on the human operator while increasing task efficiency. The performance of the collaboration is typically managed by the introduction of complex algorithms in the robot control schemes to ensure optimality of its behavior; however, a set of tools for characterizing the response of the human operator to the movement of the robot has yet to be developed.

Methods

Trunk acceleration was measured and used to define descriptive metrics during various human robot collaboration strategies. Recurrence quantification analysis was used to build a compact description of trunk oscillations.

Results and discussion

The results show that a thorough description can be easily developed using such methods; moreover, the obtained values highlight that, when designing strategies for human robot collaboration, ensuring that the subject maintains control of the rhythm of the task allows to maximize comfort in task execution, without affecting efficiency.

Disorientation effects, circulating small ribonucleic acid, and genetic susceptibility on static postural stability

Background

Motion Sickness increases risk of performance deficits and safety of flight concerns. The etiology of motion sickness is poorly understood. Here, we attempted to quantify the physiological effects of motion sickness on static balance and determine the genetic predictors associated with these effects.

Methods

16 subjects underwent a disorientation stimulus to induce motion sickness. Motion sickness susceptibility was identified using the Motion Sickness Susceptibility Questionnaire. Postural balance outcomes were measured using two tasks, and small ribonucleic acid profiles were assessed with blood draws before motion sickness stimulus. Differences in postural sway before and after the stimulus as well as effect modification of susceptibility were assessed. A random forest followed by regression tree analysis was constructed for each postural sway variable to determine top genetic and covariate predictors.

Findings

Significant differences existed in mean postural balance responses between before and after stimulus. Individuals with longer stimulus survival experienced a greater (but insignificant) perception of sway, even if not displaying increased sway for all conditions. Circulation small ribonucleic acids were differentially expressed between individuals with long and short stimulus survival, many of these microRNA have purported targets in genes related to vestibular disorders.

Interpretation

We found motion sickness produces transient motor dysfunction in a healthy military population. Small ribonucleic acids were differentially expressed between subjects with long and short stimulus survival times.

Correlation between Physical Performance and Stabilometric Parameters in Older Adults

Background and Objectives: Falls are a common and serious threat to the health and independence of older adults. The decrease in functional capacity during aging means an increased risk of falls. To date, it is not known whether there is a relationship between balance and functional tests. The aim of the study was to evaluate the correlation between eyes-open and eyes-closed static balance with different functional tests. Materials and Methods: A correlation study was designed with 52 healthy subjects over 65 years of age. Results: Regarding the open eyes stabilometric parameters, significant correlations observed between the surface and the functional tests were weak in all cases. The correlations observed between length and the functional tests performed were moderate, except for that of the Timed Up and Go test (TUG) which was weak. No significant correlation between TUG and surface was found. Regarding the closed eyes stabilometric parameters, statistically significant moderate correlations were found between the surface and the Short Physical Performance Battery (SPPB) and the Five Times Sit to Stand test (5XSST). In the case of the length with eyes closed, a statistically significant moderate correlation (rho = 0.40-0.69) was found with the SPPB and 5XSST variables, and weak correlations with the 4 m Walk Speed test (4WS) and TUG variables. Conclusions: There is a mild to moderate correlation between some functional tests and stabilometric parameters in adults over 65 years old.

Examining the ability to track multiple moving targets as a function of postural stability: a comparison between team sports players and sedentary individuals

Background

The ability to track multiple objects plays a key role in team ball sports actions. However, there is a lack of research focused on identifying multiple object tracking (MOT) performance under rapid, dynamic and ecologically valid conditions. Therefore, we aimed to assess the effects of manipulating postural stability on MOT performance.

Methods

Nineteen team sports players (soccer, basketball, handball) and sixteen sedentary individuals performed the MOT task under three levels of postural stability (high, medium, and low). For the MOT task, participants had to track three out of eight balls for 10 s, and the object speed was adjusted following a staircase procedure. For postural stability manipulation, participants performed three identical protocols (randomized order) of the MOT task while standing on an unstable platform, using the training module of the Biodex Balance System SD at levels 12 (high-stability), eight (medium-stability), and four (low-stability).

Results

We found that the ability to track moving targets is dependent on the balance stability conditions (F2,66 = 8.7, p < 0.001, η² = 0.09), with the disturbance of postural stability having a negative effect on MOT performance. Moreover, when compared to sedentary individuals, team sports players showed better MOT scores for the high-stability and the medium-stability conditions (corrected p-value = 0.008, Cohen's d = 0.96 and corrected p-value = 0.009, Cohen's d = 0.94; respectively) whereas no differences were observed for the more unstable conditions (low-stability) between-groups.

Conclusions

The ability to track moving targets is sensitive to the level of postural stability, with the disturbance of balance having a negative effect on MOT performance. Our results suggest that expertise in team sports training is transferred to non-specific sport domains, as shown by the better performance exhibited by team sports players in comparison to sedentary individuals. This study provides novel insights into the link between individual's ability to track multiple moving objects and postural control in team sports players and sedentary individuals.

Specific Posture-Stabilising Effects of Vision and Touch Are Revealed by Distinct Changes of Body Oscillation Frequencies

We addressed postural instability during stance with eyes closed (EC) on a compliant surface in healthy young people. Spectral analysis of the centre of foot pressure oscillations was used to identify the effects of haptic information (light-touch, EC-LT), or vision (eyes open, EO), or both (EO-LT). Spectral median frequency was strongly reduced by EO and EO-LT, while spectral amplitude was reduced by all "stabilising" sensory conditions. Reduction in spectrum level by EO mainly appeared in the high-frequency range. Reduction by LT was much larger than that induced by the vision in the low-frequency range, less so in the high-frequency range. Touch and vision together produced a fall in spectral amplitude across all windows, more so in anteroposterior (AP) direction. Lowermost frequencies contributed poorly to geometric measures (sway path and area) for all sensory conditions. The same subjects participated in control experiments on a solid base of support. Median frequency and amplitude of the spectrum and geometric measures were largely smaller when standing on solid than on foam base but poorly affected by the sensory conditions. Frequency analysis but not geometric measures allowed to disclose unique tuning of the postural control mode by haptic and visual information. During standing on foam, the vision did not reduce low-frequency oscillations, while touch diminished the entire spectrum, except for the medium-high frequencies, as if sway reduction by touch would rely on rapid balance corrections. The combination of frequency analysis with sensory conditions is a promising approach to explore altered postural mechanisms and prospective interventions in subjects with central or peripheral nervous system disorders.

Static balance performance differs depending on the test, age and specific role played in acrobatic gymnastics

BACKGROUND

Static balance performance appears to detect differences between roles played in team sports. Static balance can also be influenced by the subject's height and age, and the type of test used.

RESEARCH QUESTION

Could the static balance profile show differences among the role played depending on the specific test evaluated and the gymnasts' age?

METHODS

A cross-sectional design was applied. 46 acrobatic gymnasts (37 females and 9 males) were divided in four groups according to role (base or top gymnast) and stage of adolescence (early adolescent or mid-adolescent) during two different static tests: (1) unipedal with open and closed eyes (generic), and (2) headstand (specific). To test the effect of the role and the age group, a two-way analysis of variance (ANOVA) between groups was performed. Centre of pressure (COP) measurements were obtained and normalised relative to participants height, including length travelled on the anteroposterior and mediolateral axis (AP_CoP and ML_CoP) and the mean speed (SP_CoP).

RESULTS

Base gymnasts obtained lower values in the CoP excursion than Top gymnasts but only in unipedal tests for all the variables analysed (5.536 ≥ F_1,42 ≤ 10.589, 0.002 ≥ p ≤ 0.023), except for the AP_CoP in unipedal-closed. Mid-adolescent gymnasts obtained lower values in the CoP excursion regardless of the task than early adolescent (5.324 ≥ F_1,42 ≤ 14.805, 0.000 ≥ p ≤ 0.026).

SIGNIFICANCE

It has been observed a clear effect of age on the static balance manifested in acrobatic gymnastics, regardless of the subject's height, the role played, and the test performed. The effect of the role played in this team sport has been different depending on the type of test performed.

Simultaneous measurement of centre of pressure and centre of mass in assessing postural sway in healthcare workers with non-specific back pain: protocol for a cross-sectional study

INTRODUCTION

Low back pain (LBP) is widely prevalent in healthcare workers. It is associated with impaired postural and core stability. So far, centre of pressure (CoP) measures have been commonly recorded through the use of a force plate in order to assess postural stability. However, this approach provides limited information about the centre of mass (CoM) movement in the lumbar region in individuals with LBP. Recent developments in sensor technology enable measurement of the trunk motion which could provide additional information on postural sway. However, the question remains as to whether CoM measures would be more sensitive in discriminating individuals with mild and moderate back pain than traditional CoP analyses. This study aims to investigate the sensitivity of CoP and CoM measures under varied stable, metastable and unstable testing conditions in healthcare workers, and their relationship with the level of subjective reported back pain.

METHODS AND ANALYSIS

This is a cross-sectional controlled laboratory study. A group of 90 healthcare professionals will be recruited from rehabilitation centres within local areas. Participants will complete the Oswestry Disability Questionnaire. The primary outcome will be the rate of their back pain on the 0-10 Low Back Pain Scale (1-3 mild pain and 4-6 moderate pain). Secondary outcomes will include variables of postural and core stability testing during bipedal and one-legged stance on a force plate, a foam mat placed on the force plate, and a spring-supported platform with either eyes open or eyes closed. Both CoP using the posturography system based on a force plate and CoM using the inertial sensor system placed on the trunk will be simultaneously measured.

ETHICS AND DISSEMINATION

Projects were approved by the ethics committee of the Faculty of Physical Education and Sport, Comenius University in Bratislava (Nos. 4/2017, 1/2020). Findings will be published in peer-reviewed journals and presented at conferences.

Proof-of-Concept of the Virtual Reality Comprehensive Balance Assessment and Training for Sensory Organization of Dynamic Postural Control

Accurate quantification of the impact of visual, somatosensory, and vestibular systems on postural control may inform tailor-made balance intervention strategies. The aim of this proof-of-concept study was to determine the safety, sense of presence, system usability, and face validity of a newly developed Virtual Reality Comprehensive Balance Assessment and Training (VR-ComBAT) in healthy young individuals. The VR-ComBAT included six balance condition: (1) stable surface with fixed virtual reality (VR) surroundings; (2) stable surface with blacked out VR surroundings; (3) stable surface with VR visual conflict; (4) unstable surface with fixed VR surroundings; (5) unstable surface with blacked out VR surroundings; and (6) unstable surface with VR visual conflict. Safety was evaluated using the number of adverse events, including scores on the Simulator Sickness Questionnaire. Sense of presence was evaluated using the igroup Presence Questionnaire (iPQ). System usability was assessed using the Systems Usability Scale (SUS). Friedman analyses with post hoc Wilcoxon Signed Rank tests were employed to demonstrate face validity by quantifying center of pressure (COP) changes in mean distance, mean velocity, and mean frequency in the anteroposterior (AP) and mediolateral (ML) direction across the six conditions. Twenty-three participants (27.4 ± 8.0 years old; 13 women) reported no adverse events. Participants scores on average 44.9 ± 9.6 on the iPQ and 79.7 ± 9.9 on the SUS. Post hoc analyses showed significant changes in COP-based measures when compared to baseline. The mean frequency change of COP showed direction-dependence in which increased frequency change in AP was observed while decreased change in ML was noted. The VR-ComBAT provides a safe, feasible, and cost-effective VR environment that demonstrates consistent sensory re-weighting between visual, somatosensory, and vestibular systems. Future studies should investigate whether VR-ComBAT can be used to inform precision rehabilitation of balance and fall prevention in older adults without and with neurological conditions.

Internal Consistency of Sway Measures via Embedded Head-Mounted Accelerometers: Implications for Neuromotor Investigations

Accelerometers are being increasingly incorporated into neuroimaging devices to enable real-time filtering of movement artifacts. In this study, we evaluate the reliability of sway metrics derived from these accelerometers in a standard eyes-open balance assessment to determine their utility in multimodal study designs. Ten participants equipped with a head-mounted accelerometer performed an eyes-open standing condition on 7 consecutive days. Sway performance was quantified with 4 standard metrics: root-mean-square (RMS) acceleration, peak-to-peak (P2P) acceleration, jerk, and ellipse area. Intraclass correlation coefficients (ICC) quantified reliability. P2P in both the mediolateral (ICC = 0.65) and anteroposterior (ICC = 0.67) planes yielded the poorest reliability. Both ellipse area and RMS exhibited good reliability, ranging from 0.76 to 0.84 depending on the plane. Finally, jerk displayed the highest reliability with an ICC value of 0.95. Moderate to excellent reliability was observed in all sway metrics. These findings demonstrate that head-mounted accelerometers, commonly found in neuroimaging devices, can be used to reliably assess sway. These data validate the use of head-mounted accelerometers in the assessment of motor control alongside other measures of brain activity such as electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS).

Protocol for static posturography with dynamic tests in individuals without vestibular complaints using the Horus system

PURPOSE

To propose a protocol for investigating the body balance and determining reference values in different age groups and gender, using the methodology of static posturography with dynamic tests, in low-cost Brazilian equipment for diagnosing balance.

METHODS

The objectives of this study aimed to propose a protocol for investigating the body balance and determining reference values in different age groups and gender, using the methodology of static posturography with dynamic tests, in new low-cost Brazilian equipment for diagnosing balance. Method: 297 healthy volunteers, between 20 and 89 years old, without vestibular complaints, were divided into six groups according to age group and gender. Stability limits and seven sensory conditions named from C1 to C7 were evaluated. The work was carried out using Horus equipment, manufactured in Brazil.

RESULTS

The reference values of the stability limit for females and males were obtained according to the ages: from 20 to 59 (≥ 12,594 mm2 and ≥ 19,221 mm2); from 60 to 69 (≥ 7,031 mm2 and ≥ 12,161 mm2); from 70 to 89 (≥ 6,340 mm2 and ≥ 8,794 mm2). For sensory integration tests under conditions C1 to C7, as age increased, the values of the Confidence Ellipse (CE) area also increased. Reference percentile values were established for Residual Functional Balance (RFB) and Sensory Analysis (SA).

CONCLUSION

A protocol was established to investigate body balance via static posturography as well as reference values for normal individuals were determined, according to the different gender and age groups.

Are Core Stability Tests Related to Single Leg Squat Performance in Active Females?

Core stability (CS) deficits can have a significant impact on lower limb function. The aim of this study was to investigate the relationship between two dynamic core exercise assessments and dynamic knee valgus during single-leg squats. In total, 20 physically active female students participated in this study. The OCTOcore smartphone application assesses CS during two dynamic exercise tests, the partial range single-leg deadlift (SLD) test and the bird-dog (BD) test. A two-dimensional assessment of a single-leg squat test was used to quantify participants’ hip frontal angle (HFA_SLS) and knee frontal plane projection angle (FPPA_SLS). Ankle dorsiflexion was evaluated through the weight-bearing dorsiflexion test. The correlational analyses indicated that the HFA_SLS was significantly related to the partial range single-leg deadlift test (r = 0.314, p < 0.05) and ankle dorsiflexion (r = 0.322, p < 0.05). The results showed a significant difference (p < 0.05) in the CS test between cases categorised as dynamic knee valgus (>10°) and normal (≤10°). The CS deficit may influence the neuromuscular control of the lumbopelvic-hip complex during single-leg movements. The link between CS and kinematic factors related to knee injuries was only observed when CS was measured in the SLD test but not in the BD test.

Chest-Worn Inertial Sensors: A Survey of Applications and Methods

Inertial Measurement Units (IMUs) are frequently implemented in wearable devices. Thanks to advances in signal processing and machine learning, applications of IMUs are not limited to those explicitly addressing body movements such as Activity Recognition (AR). On the other hand, wearing IMUs on the chest offers a few advantages over other body positions. AR and posture analysis, cardiopulmonary parameters estimation, voice and swallowing activity detection and other measurements can be approached through chest-worn inertial sensors. This survey tries to introduce the applications that come with the chest-worn IMUs and summarizes the existing methods, current challenges and future directions associated with them. In this regard, this paper references a total number of 57 relevant studies from the last 10 years and categorizes them into seven application areas. We discuss the inertial sensors used as well as their placement on the body and their associated validation methods based on the application categories. Our investigations show meaningful correlations among the studies within the same application categories. Then, we investigate the data processing architectures of the studies from the hardware point of view, indicating a lack of effort on handling the main processing through on-body units. Finally, we propose combining the discussed applications in a single platform, finding robust ways for artifact cancellation, and planning optimized sensing/processing architectures for them, to be taken more seriously in future research.

Role of vision in static balance in persons with and without visual impairments

BACKGROUND

Vision is one of the elements of the system responsible for maintaining static balance. Any visual impairments or conditions hampering the reception of visual stimuli may affect static balance. It would be interesting to identify to what extent people with different degrees of dysfunction and in different conditions are able to compensate for the inability to receive visual stimuli while maintaining balance.

AIM

The aim of this study was to determine the role of the vision in maintaining static balance. This study sought to assess balance and the degree of compensation when the possibility of receiving visual stimuli is limited in persons without visual impairments and persons with varying degrees of visual impairments.

DESIGN

Controlled observational study.

SETTING

Main University Laboratory.

POPULATION

The study included 122 individuals, 81 of whom were visually impaired. The participants with visual impairments were divided into three groups according to their levels of disability.

METHODS

Subjects performed tests on a stabilographic platform: standing on both feet with eyes open and closed, single right- and left-leg stance with eyes open and closed. The center of pressure path length and the visual inspection indicator were analysed. Significance of differences between the groups regarding the visual inspection indicator and tests performed with eyes open and closed was assessed with the use of the Mann-Whitney U test. The effects and interactions between variables were verified using the ANOVA test for the main effects and factorial designs.

RESULTS

Differences were noted in balance of persons without visual impairments in single-leg stance tests with eyes open and closed as well as when standing on both feet with eyes open and closed. In persons with visual impairment, significant differences were observed in the single left-leg stance test with eyes open and closed only. Testing conditions and disability levels exerted a significant influence on static balance in single-leg tests.

CONCLUSIONS

The findings of the study confirm the role of vision in maintaining balance in the context of factors that may affect it, i.e. conditions (eyes open or closed) and possibilities of receiving visual stimuli (disability level).

CLINICAL REHABILITATION IMPACT

The significance of the visual effect was noted in single-leg tests. More demanding tests detect compensatory mechanisms of balance more accurately.

Physiological Vibration Acceleration (Phybrata) Sensor Assessment of Multi-System Physiological Impairments and Sensory Reweighting Following Concussion

Objective

To assess the utility of a head-mounted wearable inertial motion unit (IMU)-based physiological vibration acceleration (“phybrata”) sensor to support the clinical diagnosis of concussion, classify and quantify specific concussion-induced physiological system impairments and sensory reweighting, and track individual patient recovery trajectories.

Methods

Data were analyzed from 175 patients over a 12-month period at three clinical sites. Comprehensive clinical concussion assessments were first completed for all patients, followed by testing with the phybrata sensor. Phybrata time series data and spatial scatter plots, eyes open (Eo) and eyes closed (Ec) phybrata powers, average power (Eo+Ec)/2, Ec/Eo phybrata power ratio, time-resolved phybrata spectral density (TRPSD) distributions, and receiver operating characteristic (ROC) curves are compared for individuals with no objective impairments and those clinically diagnosed with concussions and accompanying vestibular impairment, other neurological impairment, or both vestibular and neurological impairments. Finally, pre- and post-injury phybrata case report results are presented for a participant who was diagnosed with a concussion and subsequently monitored during treatment, rehabilitation, and return-to-activity clearance.

Results

Phybrata data demonstrate distinct features and patterns for individuals with no discernable clinical impairments, diagnosed vestibular pathology, and diagnosed neurological pathology. ROC curves indicate that the average power (Eo+Ec)/2 may be utilized to support clinical diagnosis of concussion, while Eo and Ec/Eo may be utilized as independent measures to confirm accompanying neurological and vestibular impairments, respectively. All 3 measures demonstrate area under the curve (AUC), sensitivity, and specificity above 90% for their respective diagnoses. Phybrata spectral analyses demonstrate utility for quantifying the severity of concussion-induced physiological impairments, sensory reweighting, and subsequent monitoring of improvements throughout treatment and rehabilitation.

Conclusion

Phybrata testing assists with objective concussion diagnosis and provides an important adjunct to standard concussion assessment tools by objectively ascertaining neurological and vestibular impairments, guiding targeted rehabilitation strategies, monitoring recovery, and assisting with return-to-sport/work/learn decision-making.

Validity and Reliability of the Satel 40 Hz Stabilometric Force Platform for Measuring Quiet Stance and Dynamic Standing Balance in Healthy Subjects

BACKGROUND

A force platform must have validity and reliability for optimal use. The objective of this study was to analyze the validity and the reliability of the Satel 40 Hz stabilometric force platform.

METHODS

A study of instrumental validity and reliability, involving a cross-sectional correlational and comparative analysis was performed. To determine the validity, four certified weights located on three axes were used and the ability of the stabilometric force platform to detect changes in the position of the different axes was observed. A test-retest was performed to analyze the reliability. Forty-two symptom-free volunteers participated in the study. Assessments were taken in a standing static position and in a dynamic position, with the eyes open and closed. Three measurements were taken and the intra-class correlation coefficient (ICC) was calculated.

RESULTS

The validity increased as the weight increased for all the variables measured in the stabilometric parameters (p < 0.05). The reliability was shown to be good to excellent for the two visual conditions. The positional variables obtained a higher ICC. The variable with the best ICC was the Y mean in OE (ICC 0.874 and a p < 0.001). All the values showed an increase in a dynamic situation.

CONCLUSION

The findings support the reliability and validity of the Satel 40 Hz stabilometric force platform. The platform could be recommended to evaluate static and dynamic standing balance in healthy adult individuals. Guidelines for treatment and the level of quality of stabilometry could be obtained from its use.

Specific Motor and Cognitive Performances Predict Falls during Ward-Based Geriatric Rehabilitation in Patients with Dementia

The aim of this study was to identify in-hospital fall risk factors specific for multimorbid hospitalized geriatric patients with dementia (PwD) during hospitalization. Geriatric inpatients during ward-based rehabilitation (n = 102; 79.4% females; 82.82 (6.19) years of age; 20.26 (5.53) days of stay) were included in a comprehensive fall risk assessment combining established clinical measures, comprehensive cognitive testing including detailed cognitive sub-performances, and various instrumented motor capacity measures as well as prospective fall registration. A combination of unpaired t-tests, Mann-Whitney-U tests, and Chi-square tests between patients with ("in-hospital fallers") and without an in-hospital fall ("in-hospital non-fallers"), univariate and multivariate regression analysis were used to explore the best set of independent correlates and to evaluate their predictive power. In-hospital fallers (n = 19; 18.63%) showed significantly lower verbal fluency and higher postural sway (p < 0.01 to 0.05). While established clinical measures failed in discriminative as well as predictive validity, specific cognitive sub-performances (verbal fluency, constructional praxis, p = 0.01 to 0.05) as well as specific instrumented balance parameters (sway area, sway path, and medio-lateral displacement, p < 0.01 to 0.03) significantly discriminated between fallers and non-fallers. Medio-lateral displacement and visuospatial ability were identified in multivariate regression as predictors of in-hospital falls and an index combining both variables yielded an accuracy of 85.1% for fall prediction. Results suggest that specific cognitive sub-performances and instrumented balance parameters show good discriminative validity and were specifically sensitive to predict falls during hospitalization in a multimorbid patient group with dementia and an overall high risk of falling. A sensitive clinical fall risk assessment strategy developed for this specific target group should include an index of selected balance parameters and specific variables of cognitive sub-performances.