Postural Behavior Research Articles

Simulation of Pregnancy-Related Abdominal Mass Results in Nonimmediate Changes in Postural Control: An Exploratory Study

Background: Changes to segmental inertial properties, abdominal growth, and increased circulating relaxin are some of the numerous contributing factors to higher risks of falling during pregnancy. These factors emerge in different phases of pregnancy, have a cumulative effect, and vary across women. For these reasons, determining each factor's role in the development of higher fall risk is challenging and yet crucial in uncovering their clinical importance. Objectives: To investigate the independent effect of additional abdominal weight on balance control in nonpregnant women. Study Design: A longitudinal study. Methods: Ten healthy women were submitted to computerized posturography while an additional abdominal weight (7% of body mass) was applied for 24 hours. Postural behavior was recorded from 4 experimental conditions: before placement of the additional weight (Baseline), immediately after placement of the abdominal weight (T1), 24 hours after continuous application of the abdominal weight (T2), and immediately after abdominal weight removal (T3). Variables of interest were extracted from the participant's body sway dynamics and included the center of pressure (COP) migration area, range, root mean square (RMS), mean velocity, median frequency (F50), and signal sample entropy (SEnt). Results: At T3, significant increases were found for the COP migration area, mediolateral range, and mediolateral RMS (P values range: .005-.013). Also at T3, significant decreases were found for mediolateral F50 and SEnt (P values range: .001-.038). Conclusion: Modifications in balance behavior were observed when the abdominal weight was removed after 24 hours of application. Significant changes occurred in the mediolateral body sway amplitude and regularity suggesting the presence of mediolateral instability.

Efficient Detection Method of Pig-Posture Behavior Based on Multiple Attention Mechanism.

Due to the low detection precision and poor robustness, the traditional pig-posture and behavior detection method is difficult to apply in the complex pig captivity environment. In this regard, we designed the HE-Yolo (High-effect Yolo) model, which improves the Darknet-53 feature extraction network and integrates DAM (Dual attention mechanism) of channel attention mechanism and space attention mechanism, to recognize the posture behaviors of the enclosure pigs in real-time. First, the pig data set is clustered and optimized by the K-means algorithm to obtain a new anchor frame size. Second, the DSC (Depthwise separable convolution) and h-switch activation function are innovatively introduced into the Darknet-53 feature extraction network, and the C-Res (Contrary residual structure) unit is designed to build Darknet-A feature extraction network, so as to avoid network gradient explosion and ensure the integrity of feature information. Subsequently, DAM integrating the spatial attention mechanism and the channel attention mechanism is established, and it is further combined with the Incep-abate module to form DAB (Dual attention block), and HE-Yolo is finally built by Darknet-A and DAB. A total of 2912 images of 46 enclosure pigs are divided into the training set, the verification set, and the test set according to the ratio of 14 : 3:3, and the recognition performance of HE-Yolo is verified according to the parameters of the precision P, the recall R, the AP (i.e., the area of P-R curve) and the MAP (i.e., the average value of AP). The experiment results show that the AP values of HE-Yolo reach 99.25%, 98.41%, 94.43%, and 97.63%, respectively, in the recognition of four pig-posture behaviors of standing, sitting, prone and sidling of the test set. Compared with other models such as Yolo v3, SSD, and faster R–CNN, the mAP value of HE-Yolo is increased by 5.61%, 4.65%, and 0.57%, respectively, and the single-frame recognition time of HE-Yolo is only 0.045 s. In the recognition of images with foreign body occlusion and pig adhesion, the mAP values of HE-Yolo are increased by 4.04%, 4.94%, and 1.76%, respectively, while compared with other models. Under different lighting conditions, the mAP value of HE-Yolo is also higher than that of other models. The experimental results show that HE-Yolo can recognize the pig-posture behaviors with high precision, and it shows good generalization ability and luminance robustness, which provides technical support for the recognition of pig-posture behaviors and real-time monitoring of physiological health of the enclosure pigs.

The Walls Are Closing In: Postural Responses to a Virtual Reality Claustrophobic Simulation

Background: Changes in the visual environment and thereby, the spatial orientation, can induce postural instability leading to falls. Virtual reality (VR) has been used to expose individuals to virtual environments (VE) that increase postural threats. Claustrophobia is an anxiety disorder categorized under situational phobias and can induce such postural threats in a VE. Purpose: The purpose of the study was to investigate if VR-generated claustrophobic simulation has any impact on postural threats that might lead to postural instability. Methods: Thirty healthy men and women (age: 20.7 ± 1.2 years; height: 166.5 ± 7.3 cm; mass: 71.7 ± 16.2 kg) were tested for postural stability while standing on a force platform, upon exposure to five different testing trials, including a normal stance (NoVR), in stationary VE (VR), and three consecutive, randomly initiated, unexpected claustrophobia trials (VR CP1, VR CP2, VR CP3). The claustrophobia trials involved all four walls closing in towards the center of the room. Center of pressure (COP)-derived postural sway variables were analyzed with a one-way repeated measures analysis of variance at an alpha level of 0.05. Results: Significant main effect differences existed in all but one dependent COP-derived postural sway variables, at p < 0.05. Post-hoc pairwise comparisons with a Bonferroni correction revealed that, predominantly, postural sway excursions were significantly lower in claustrophobia trials compared to NoVR and VR, but only accomplished with significantly increased sway velocity. Conclusion: The VR CP trials induced lower postural sway magnitude, but with increased velocity, suggesting a bracing and co-contraction strategy when exposed to virtual claustrophobic postural threats. Additionally, postural sway decreased with subsequent claustrophobia trials, suggesting potential motor learning effects. Findings from the study offer insights to postural control behavior under virtual claustrophobic simulations and can aid in VR exposure therapy for claustrophobia.

Persistent Postural-Perceptual Dizziness (PPPD) from Brain Imaging to Behaviour and Perception.

Persistent postural-perceptual dizziness (PPPD) is a common cause of chronic dizziness associated with significant morbidity, and perhaps constitutes the commonest cause of chronic dizziness across outpatient neurology settings. Patients present with altered perception of balance control, resulting in measurable changes in balance function, such as stiffening of postural muscles and increased body sway. Observed risk factors include pre-morbid anxiety and neuroticism and increased visual dependence. Following a balance-perturbing insult (such as vestibular dysfunction), patients with PPPD adopt adaptive strategies that become chronically maladaptive and impair longer-term postural behaviour. In this article, we explore the relationship between behavioural postural changes, perceptual abnormalities, and imaging correlates of such dysfunction. We argue that understanding the pathophysiological mechanisms of PPPD necessitates an integrated methodological approach that is able to concurrently measure behaviour, perception, and cortical and subcortical brain function.

Differences in postural control between healthy and subjects with chronic ankle instability

IntroductionChronic ankle instability (CAI) is characterized by the occurrence of repetitive inversion mechanism of the ankle, resulting in numerous ankle sprains. CAI occurs in approximately 70% of patients with a history of a lateral ankle sprain. Many causes of functional ankle instability have been postulated and include deficits in proprioception, impaired neuromuscular-firing patterns, disturbed balance and postural control. ObjectiveThe purpose of this study was to compare postural control behaviour in subjects with chronic ankle instability and healthy subjects, using the traditional linear and nonlinear variables for the centre of pressure (CoP) displacement, during one-leg stance on stable and unstable surfaces. Methods16 CAI subjects and 20 healthy subjects were evaluated with the single leg stance on a stable surface and an unstable surface, for 60 s with a force plate. The traditional linear variables like CoP displacement, CoP amplitude and CoP velocity were calculated. Variability of CoP displacement was also submitted to nonlinear analysis and the approximated entropy, sample entropy, correlation dimension and Lyapunov exponent were calculated. ResultsOn the stable surface, no differences between groups for all the traditional variables were found but the correlation dimension of CoP mediolateral displacement had lower values on the CAI group with statistical significance (p < 0.05). On the unstable surface, no differences were found neither with linear variable neither with variability nonlinear analysis. ConclusionCorrelated dimension of CoP displacement during one-leg stance on a stable surface was the only variable that show significant differences between the two groups. The lower values of this variable in the CAI subjects may implicate a balance control system with more difficulties to adapt to the environment and the task demands. More studies are needed to better understand CAI subjects balance control.

Influence of serial subtraction tasks on transient characteristics of postural control.

We sought to better understand the influence of cognitive perturbations on transient aspects of postural control. Twenty healthy, younger adults had their postural control assessed during eyes open quiet stance. Participants completed three different conditions that either had no cognitive perturbation present, an easy cognitive perturbation (i.e., serial subtraction by ones), or a more difficult cognitive perturbation (i.e., serial subtraction by sevens). All trials finished with 60s of undisturbed eyes open quiet stance, which was the focus of the balance assessment. 95% confidence ellipse area (EA) was calculated for 5-s epochs throughout the trial. The difference in EA from the first epoch after participants started (onset) or stopped (offset) the cognitive task to the last epoch of the trial (i.e., 55-60s after perturbation) was used to characterize transient postural control behavior. Functional near-infrared spectroscopy was also used to quantify changes in prefrontal cortex activation during the counting tasks to support interpretation of the transient balance findings. There was a significant effect of condition for transient balance characteristics following a cognitive perturbation (P<0.001), with greater transient increases in postural sway for both difficult (Cohen's d=0.40, P<0.001) and easier (Cohen's d=0.29, P=0.013) cognitive perturbations relative to no cognitive perturbation. The onset of cognitive tasks was also associated with greater transient increases in postural sway than the offset of the cognitive tasks (Cohen's d=0.24, P=0.019). The functional near-infrared spectroscopy data indicated that a significant decrease in deoxygenated hemoglobin was observed for left Brodmann area 46 for both the subtraction by ones (T=-3.97; Benjamini-Hochberg significance value (q)=0.008) and subtraction by sevens (T=-3.11; q=0.036) conditions relative to the baseline condition. The subtraction by sevens condition was also associated with a relative increase in deoxygenated hemoglobin for the right Brodmann area 9 (T=3.36; q=0.026) compared to the subtraction by ones condition. In conclusion, serial subtraction can elicit transient increases in postural sway, with more difficult tasks and the onset of the cognitive-motor challenge exhibiting magnified effects. Additionally, even the cessation of a cognitive task (i.e., serial subtraction) can be associated with lingering perturbing effects on balance control.

Postural Complexity during Listening in Young and Middle-Aged Adults.

Postural behavior has traditionally been studied using linear assessments of stability (e.g., center of pressure ellipse area). While these assessments may provide valuable information, they neglect the nonlinear nature of the postural system and often lead to the conflation of variability with pathology. Moreover, assessing postural behavior in isolation or under otherwise unrealistic conditions may obscure the natural dynamics of the postural system. Alternatively, assessing postural complexity during ecologically valid tasks (e.g., conversing with others) may provide unique insight into the natural dynamics of the postural system across a wide array of temporal scales. Here, we assess postural complexity using Multiscale Sample Entropy in young and middle-aged adults during a listening task of varying degrees of difficulty. It was found that middle-aged adults exhibited greater postural complexity than did young adults, and that this age-related difference in postural complexity increased as a function of task difficulty. These results are inconsistent with the notion that aging is universally associated with a loss of complexity, and instead support the notion that age-related differences in complexity are task dependent.

Automatic driver cognitive fatigue detection based on upper body posture variations

Driver cognitive fatigue can significantly affect driving and may lead to fatal accidents. In this regard, automatic detection of underload driver cognitive fatigue based on upper body posture dynamics is studied in this paper, where a semi-supervised approach is developed to identify the cognitive fatigue patterns of driver posture. Initially, an unsupervised Gaussian Mixture Model (GMM) clustering is applied to the acceleration data representing the driver’s head, neck, and sternum obtained in a simulated driving through a motion capture suit. This provides the optimum clusters of the most-similar and correlated time-series data of driver upper posture. Then, an automatic labelling algorithm is developed that mines the maximal value and the standard deviation of each GMM cluster and assigns a symbol according to the discrepancy in postural behaviour. Finally, novel machine learning supervised classifiers, including Gaussian Support Vector Machines, and Bootstrap-Aggregating based Ensemble Classifiers, are trained on the GMM-labelled upper body posture dataset, as real-time algorithms, to detect the driver fatigue. The proposed method was validated against cognitive fatigue measured through a neurophysiological method based on an electroencephalogram. The results show that the proposed semi-supervised approach outperforms the existing state-of-art systems in accurately detecting the cognitive fatigue patterns. It successfully recognizes different driving postures with accuracies of 93% and 90% for two test subjects. The shortcomings of the proposed work and directions for potential expansion of current work are discussed.

Impact of El-Poems study: the e-learning for postural education in music students: a randomized controlled trial protocol

BackgroundMusculoskeletal pain (MP) has today intensified in a large proportion of music students in Iran. Poor posture while playing an instrument is thus assumed as a very significant risk factor affecting such a condition in this population. The present study aims to evaluate the impact of electronic learning (e-learning) for postural education to music students on posture behavior and MP (abbreviated as an El-Poems study).MethodsThis study is a matched-pair, two-arm, parallel randomized controlled trial (RCT). The participants, as the 7th-to-12th-grade music students, will be accordingly assigned to intervention (n = 204) and control (n = 204) groups, based on the inclusion and exclusion criteria. The postural education will be also presented through the web-based Student Education Network (with the acronym, SHAD) at the Tehran Conservatory of Music, Tehran, Iran. The intervention program consists of four sessions, using the Integrated Change (I-Change) model. It will be also implemented by a trained physical education instructor and a health educator. The content of the program includes raising awareness, building motivation, and developing skills. Besides, its components are comprised of specific proper postures viz. standing, sitting, lifting, carrying, and hand position while playing a musical instrument. The primary outcome is the MP that will be assessed by the Nordic Body Map (NBM) questionnaire and a numerical rating scale (NRS), and the secondary outcome is the posture behavior that will be evaluated objectively, using the Rapid Entire Body Assessment (REBA) tool. The data will be also collected at baseline and after a six-month follow-up.ConclusionThis RCT is an innovative study as a pioneer to represent the first attempt for web-based postural education as well as an attractive intervention to prevent MP in Iranian music students.Trial registrationCurrent Controlled Trials IRCT20180528039885N2. Prospectively registered on 11 September 2021

Postural behavior recognition of captive nocturnal animals based on deep learning: a case study of Bengal slow loris

The precise identification of postural behavior plays a crucial role in evaluation of animal welfare and captive management. Deep learning technology has been widely used in automatic behavior recognition of wild and domestic fauna species. The Asian slow loris is a group of small, nocturnal primates with a distinctive locomotion mode, and a large number of individuals were confiscated into captive settings due to illegal trade, making the species an ideal as a model for postural behavior monitoring. Captive animals may suffer from being housed in an inappropriate environment and may display abnormal behavior patterns. Traditional data collection methods are time-consuming and laborious, impeding efforts to improve lorises’ captive welfare and to develop effective reintroduction strategies. This study established the first human-labeled postural behavior dataset of slow lorises and used deep learning technology to recognize postural behavior based on object detection and semantic segmentation. The precision of the classification based on YOLOv5 reached 95.1%. The Dilated Residual Networks (DRN) feature extraction network showed the best performance in semantic segmentation, and the classification accuracy reached 95.2%. The results imply that computer automatic identification of postural behavior may offer advantages in assessing animal activity and can be applied to other nocturnal taxa.

Bening paraxysmal torticollis is a sensoriomotos trigeminocervical convergence merchanisms? Experimental evidence.

Introduction Benign paroxysmal torticollis (BPT) is likely an age-sensitive, childhood periodic syndromes that are commonly precursors of migraine, with atypical postural behavior (torticollis) to start early and self-limited, which of unknown etiology. Objective To prove the existence of forms of sensorimotor convergence between the trigeminal nerve and upper cervical roots respectively. Methods Ninety-five rats Norvegicus were submitted to infraorbital nerve blockade using botulinum neurotoxin type A (BoNT/A) (n=48) controlled by isotonic saline solution animals (ISS) (n=47). After 84 days the animals were evaluated on their motor functions using open field test and postural behavior. Results Of the 48 animals in the BoNT/A group one animal showed the torticollis ipsilateral to BoNT/A injection. The macroscopic analysis showed fasciculations on clavotrapezius muscle. The biopsy with optical and electronic microscopy of this muscle showed changes suggestive of denervation secondary to BoNT/A. Conclusion We suggested the existence of a pathway sensoriomotor probably in the brainstem involves the trigeminal system and cervical motoneurons.

Effects of farrowing hut design on maternal and thermoregulatory behaviour in outdoor housed sows and piglets

This study aimed to determine the effect of three different farrowing huts on the behaviour of outdoor housed sows and piglets during summer in Eastern Canada, with a focus on thermoregulatory and crushing behaviours. Forty-two second parity sows were housed outdoors in groups of three during lactation (N = 42). Within each group, sows had access to three farrowing huts: a Wood modified A-frame hut, a Plastic round calf hutch, and a Metal ark English-style hut. Cameras were installed in the huts to observe behaviour on days 1, 2, 7 and 14 of lactation. Temperature and humidity were recorded outside and inside the huts. Hourly temperature averages were analysed for the effect of the hut type for day and night separately. Sows farrowed in the huts between August and October and observations of sow and piglet location, posture, nursing, and crushing events were collected in the morning and afternoon. The Wood huts showed the least variation in temperature between days and nights, with the Metal huts showing similar thermal properties to the Wood huts (P < 0.05). The Plastic hut was hotter and drier during the day, but cooler and more humid during the night (P < 0.05). No hut type effect was observed on sow use of the hut, posture, or nursing behaviour. Piglets showed greater expression of thermoregulating behaviour in the morning on day two in the Wood hut as it was the coolest (P = 0.03). Huddling was found to be the most common technique employed by piglets for thermoregulation in all huts, representing 61.2–73.8% of their time. Piglets were in contact with the sow 10.6–16.1% of the time while not nursing. The percentages of sows killing at least one piglet by crushing or trauma during the first week after farrowing were 93%, 86% and 43% for Wood, Plastic, and Metal huts, respectively (P = 0.02). Mortalities during the first week due to crushing or trauma were 18%, 15%, and 11% of liveborn piglets for the Wood, Plastic, and Metal huts, respectively (P = 0.44). The riskiest time for piglets, in terms of being crushed was found to be when the sow was standing (P = 0.04). This study suggests that the indoor risk factors for crushing change when sows are housed in huts. The Metal hut appears to be the best compromise considering thermal environment, behaviour, and litter survival, but the results suggest a need for future research into hut designs for farrowing sows on pasture to reduce crushing risks.

Feeding postural behaviors and food geometric and material properties in bearded capuchin monkeys (Sapajus libidinosus)

ObjectivesFoods that are geometrically and mechanically challenging to eat have been associated with specializations in feeding behavior and craniodental morphology across primates, and many of these foods are embedded, requiring a variety of positional behaviors during feeding. However, variation in positional behaviors in response to food properties is not well understood. Here, we examine differences in feeding postural behaviors across feeding events in relation to substrate and food geometric and material properties in a species of extractive foragers, bearded capuchins (Sapajus libidinosus).Methods and materialsWe coded over 1400 co‐occurring postural and feeding behaviors, their durations, and relative sizes of substrate and food from videos recorded at Fazenda Boa Vista in Gilbués, Piauí, Brazil. Food material properties were measured from foods collected at the time of the video recordings.ResultsOur results suggest that bearded capuchin feeding postures significantly differ across the feeding sequence, with substrate size, and between foods of high and low toughness and elastic modulus. Feeding postures were less variable for highly mechanically challenging foods. Food size also had a significant effect on postural behaviors. Large foods were more likely to be associated with suspended postures and small foods with sitting and squatting. Feeding postural behaviors were best explained by a combination of substrate and food variables.ConclusionsOur results indicate that food geometric and mechanical properties have a significant influence on feeding postural behaviors in bearded capuchins. We posit that feeding postural behaviors reflect a combination of substrate variables and food properties, and large, mechanically challenging foods have a limiting effect on postural variation.

Lumbopelvic postural differences in adolescent idiopathic scoliosis: A pilot study

BackgroundA primary etiology of adolescent idiopathic scoliosis (AIS) is currently unknown, but poor postural control of the spinal extensor musculature has been identified as an AIS risk factor. Identifiable postural differences would aid in advancing the precise postural behaviors that should be modified during Physiotherapy Scoliosis Specific Exercise (PSSE) to help limit the progression of AIS. Research questionAre there any determinable differences in lumbopelvic posture or range of motion between subjects with AIS and controls? MethodsThis prospective cohort pilot study consisted of 53 subjects (27 AIS and 26 control) aged 11–17 years. Subjects had their lumbopelvic posture assessed and monitored using the ViMove DorsaVi sensor package. All subjects underwent a live assessment to obtain initial lumbopelvic (LP) range of motion (ROM) measurements. Subjects were then monitored while continuing with normal activities of daily living (ADLs) for 12 h. With an alpha level of 0.05, nonparametric analyses were performed for each variable via a Mann-Whitney U-test. ResultsDuring the live assessment, controls exhibited a significantly greater anterior pelvic tilt ROM in the sitting position than the AIS group (p = 0.0433). When compared to female controls, females with AIS had a sitting pelvic tilt ROM that was significantly more retroverted (p = 0.0232) and less anteverted (p = 0.0010). During ADLs, female controls exhibited a higher total number of extension events than their female with AIS (p = 0.0263). These associations did not strengthen with greater spinal deformity. SignificanceThis work demonstrates postural differences between patients with AIS and controls. Further study is necessary to determine why patients with AIS adopt these postures, and if PSSEs can be utilized to limit the progression of AIS.

PROTOCOL: The effect of education programmes for improving knowledge of back health, ergonomics and postural behaviour in university students: A systematic review.

This is the protocol for a Campbell review. The objectives are as follows:To investigate the evidence on the effectiveness of education programmes in improving the knowledge of back health, ergonomics and postural behaviour in University students.

Influence of the base of support widths on postural control and feet loading symmetry during squat – preliminary study

Purpose: The symmetry of feet loading and adequate postural control are crucial aspects of proper squat performance. The study aimed to evaluate the effect of various stance widths during squat on postural control and symmetry of feet loading. Methods: Thirty healthy individuals participated in this study. Each participant performed one type of squat with a narrow stance (NS), hip stance (HS) and wide stance (WS). Results: A significantly higher value of CoP path length, the velocity of sways and Area95 were obtained for the WS squat compared to NS and HS. In addition, the wide feet setting significantly affected not only the feet loading symmetry but also the strategy (high LyE), the amount of irregularities (high SampEn) and the CoP time-series roughness complexity (high FD). It has been shown that as the base of support grew, the asymmetry index grew. Conclusions: The wide squat is less stable, requiring more complex postural control behavior and more flexibility. Performing this squat significantly shifts the pressure to the dominant limb.

Best Features Selection for the Implementation of a Postural Sway Classification Methodology on a Wearable Node

The possibility of identifying potential altered postural status in frail people, including patients with Parkinson Disease, represents an important clinical outcome in the management of frail elderly subjects, since this could lead to greater instability and consequently an increased risk of falling. Several solutions proposed in the literature for the monitoring of the postural behavior use infrastructure-dependent approaches or wearable devices, which do not allow to distinguish among different kinds of postural sways. In this paper a low cost and effective wearable solution to classify four different classes of postural behaviors (Standing, Antero-Posterior, Medio-Lateral and Unstable) is proposed. The solution exploits a sensor node, equipped by a tri-axial accelerometer, and a dedicated algorithm implementing the classification task. Different quantities are proposed to assess performance of the proposed strategy, with particular regards to the system capability to correctly classify an unknown pattern, through the index Q%, and the Reliability Index, RI%. Results achieved across a wide dataset demonstrated the suitability of the methodology developed, with Q%=99.84% and around 70% of classifications showing a RI% above 65%.

Real-time postural training effects on single and multi-person ergonomic risk scores

This article proposes and comments on the results achieved in recent laboratory testing activities to develop single and multi-person postural assessment and training in real-time. Research is carried out using the WEM-platform and is promising both in post-processing and in real-time analysis in manufacturing and logistics settings. Laboratory tests are conducted to quantify the impact of visual feedback intervention on workers’ behavior based on individual experience and to determine the effect that different anthropometric characteristics can have on ergonomic risk score. Two inertial Motion Capture systems are jointly adopted and coupled with the WEM-platform to quantify the ergonomic risk of two operators employed in a multi-manned assembly station. The results are promising both in single and multi-manned configuration: the system is able to correct the postural behavior of workers when performing the tasks. Furthermore, the flexibility of the proposed platform permits a real-time ergonomic risk assessment for both the workers involved in the study and allow to investigate their mutual movements and collaborative tasks.

Recognition of arm and body postures as social cues for proactive HRI

AbstractArtificial agents can uplift the living standards of domestic population considerably. One hindrance for this is that the robot is less competent to perceive complex human behaviors. With such perceptive skills in the robot, nonexpert users will find it easier to cope with their robot companion with less and less instructions to follow. Perception of the internal state of a user or “user situation” before interaction is crucial in this regard. There are a variety of factors that affect this user situation. Out of these, posture becomes prominent in displaying the emotional state of a person. This article presents a novel approach to identify diverse human postures often encountered in domestic environments and how a robot could assess its user’s emotional state of mind before an interaction based on postures. Therefore, the robot evaluates posture and the overall postural behavior of its user throughout the period of observation before initiating an interaction with its user. Aforementioned user evaluation is nonverbal and decisions are made through observation as well. We introduced a variable called “valence” to measure how “relaxed” or “stressed” a user is, in a certain encounter. The robot decides upon an appropriate approach behavior accordingly. Furthermore, the proposed concept was capable of recognizing both arm and body postures and both postural behaviors over time. This leads to an interaction initiated by robot itself in a favorable situation so that the scenario looks more intelligent. Hence more humanlike. The system has been implemented, and experiments have been conducted on an assistive robot placed in an artificially created domestic environment. Results of the experiments have been used to validate the proposed concept and critical observations are discussed.

The Effect of Cognitive Task on Postural Control Dynamic Regularity of Athletes With Chronic Ankle Instability When Standing on an Unstable Surface

Background and Objectives: Postural control disorder is a common complication in patients with Chronic Ankle Instability (CAI). The present study aimed to investigate the effect of dual cognitive task on postural control behavior with regard to the Center of Pressure (CoP) signal regularity while standing on an unstable surface in athletes with CAI. Methods: In the present study, 58 men participated in two groups of healthy and patients with CAI. The CoP signal was examined in 4 different unstable states on the wobble board located at the center of the force plate. The regularity of the signals recorded from the force plate was investigated using sample entropy in two directions: anterior-posterior and medial-lateral. Results: In both groups, there was a significant difference in CoP’s sample entropy signal when performing a cognitive task with a postural task (P&lt;0.001). There was a significant difference between the two groups in the cognitive task and the single task in the anteroposterior direction while standing on two legs. Conclusion: During dual tasks, the patients with CAI have a more dynamic regularity in the CoP signal than their normal counterparts. In the dual-task condition, more irregularities are observed in the CoP signal of healthy individuals. In unstable conditions, patients with CAI decrease the adaptability of postural control behavior with increasing CoP signal regularity.