Search

The existence of a learning effect by which subjects progressively reduce body sway over the course of repetitive stabilometric measurements is currently debated. Also, the position and orientation of the feet on the platform can have a substantial influence on the outcome measurements. The aim of the present work was to assess the effect of feet positions on mean total velocity (V) of the center of pressure and the area (AR) covered by its displacements during quiet standing. A group of 35 healthy young subjects was examined during two successive sessions consisting of five recordings with their feet placed either in the recommended (standard, SP) or their usual most comfortable (UP) position. Results show a slight decreasing trend that failed to be statistically significant checked with Friedman's ANOVA (SP AR, χ2(4)=6.10, p=0.19 and V, χ2(4)=8.66, p=0.07 and UP AR, χ2(4)=2.32, p=0.68 and V, χ2(4)=1.19, p=0.88). Nonetheless, values of AR and V showed a notable decrement especially evident in the SP exam reaching, respectively, 24% and 11% from baseline, whereas variability measured by the coefficient of variation was the same in the two exams. Given the results, a learning effect should not be ruled out with confidence. Also, usual foot placement would be preferable to avoid this effect. Further research is needed to take into consideration the great variability of stabilometric measurements and the fact that different subjects could adapt more readily to the test conditions than others.

Background: Postural control impairments following a stroke have impact on mobility, reduce independence and increase the risk of falls. Assessing these impairments during tasks representative of real-life situations, such as quiet standing (QS) and voluntary stepping response (VSR) will enhance our understanding of how the postural control system is impaired in individuals post-stroke (IPS). It will also inform the development of a more targeted and effective rehabilitation to prevent falls in IPS.\ud Objectives: Identify the postural control impairments encountered by IPS during QS and VSR. \ud Methods: Twenty IPS and sixteen healthy controls were recruited to perform QS and VSR tasks while ground reaction forces and whole-body motion were measured. Displacement and speed variation of the COM, centre of pressure (COP) displacement and spatiotemporal data were calculated and compared between groups. \ud Results: During QS, IPS exhibited greater maximal COP displacement in mediolateral direction, COM displacement in vertical direction and COM speed excursions compared to controls. During VSR, IPS exhibited smaller step length, braking force, posterior foot placement in relation to the pelvis and COM anteroposterior excursion compared to controls. IPS presented less static and dynamic postural stability compared to controls. \ud Conclusions: Greater postural sway during QS, smaller anteroposterior COM displacement before losing balance and altered voluntary recovering steps during VSR could place IPS at more risk of falling when they face a postural challenge in the community. These novel results will improve the current knowledge base and should be considered in IPS rehabilitation.

International audience; The study of human balance recovery strategies is important for human balance rehabilitation and humanoid robot balance control. To date, many efforts have been made to improve balance during quiet standing and walking motions. Arm usage (arm strategy) has been proposed to control the balance during walking motion in the literature. However, limited research exists on the contributions of the arm strategy for balance recovery during quiet standing along with ankle and hip strategy. Therefore, in this study, we built a simplified model with arms and proposed a controller based on nonlinear model predictive control to achieve human-like balance control. Three arm states of the model, namely, active arms, passive arms, and fixed arms, were considered to discuss the contributions of arm usage to human balance recovery during quiet standing. Furthermore, various indexes such as root mean square deviation of joint angles and recovery energy consumption were verified to reveal the mechanism behind arm strategy employment. In this study, we demonstrate to computationally reproduce human-like balance recovery with and without arm rotation during quiet standing while applying different magnitudes of perturbing forces on the upper body. In addition, the conducted human balance experiments are presented as supplementary information in this paper to demonstrate the concept on a typical example of arm strategy.

Background: The Informational Manual Therapy (IMT) is a therapeutic touch. This study aims to assess the effect of IMT on quiet standing, pain and health status in university population. Methods: An experiment was conducted on subjects utilizing a comparative paired analysis both before and after the intervention. One IMT session was performed on 57 healthy individuals aged from 18 to 65 years. The primary outcome was quiet standing assessed by the Satel 40 Hz stabilometric force platform. Secondary outcomes were bodily pain assessed by the 36-Item Short Form Survey (SF-36) and health status by EQ-5D-3L. The primary outcome was evaluated before and immediately after treatment. Results: The individuals were divided into 3 age groups, 18–35 (52.6%), 35–50 (29.8%) and 51–65 (17.6%). Statistically significant differences were immediately observed after the session ended when comparing the pre-post quiet stance scores in a number of length parameters: L, Lx, Ly and stabilometry amplitude on Y-axis with eyes open and closed. Significant differences were also found when testing bodily pain (SF-36) and anxiety (5Q-5D-3L). Conclusion: One session of IMT produced positive effects when testing quiet standing with eyes open and eyes closed, as well as a significant reduction in pain and anxiety for those tested. Further research is suggested. info:eu-repo/semantics/publishedVersion

Background: Astronauts returning to earth usually demonstrate reduced orthostatic tolerance when assessed on a tilt table or quiet standing, but no studies have evaluated postflight orthostatic tolerance during activities of daily living, when it is most clinically relevant. Ambulatory blood pressure (BP) variability also is associated with orthostatic intolerance in certain patient populations and can capture clinically significant orthostatic hypotension during activities of daily living, especially when measured on a beat-to-beat basis. We evaluated the impact of prolonged spaceflight on orthostatic tolerance and BP profiles in astronauts. Methods: Ambulatory beat-to-beat BP was recorded using a portable device for multiple 24-hour time periods before, during, and after 6 months of spaceflight in 12 astronauts (4 women; age 48±5 [mean±SD] years). BP variability in the time domain was calculated as the SD. Systolic BP distribution during activities of daily living was characterized by skewness and kurtosis. Results: In contrast with results from previous studies that used tilt tables or stand tests, no astronaut experienced orthostatic intolerance/hypotension during activities of daily living before or after spaceflight. Also, 24-hour systolic BP decreased in space (120±10 mm Hg before spaceflight versus 106±9 mm Hg during spaceflight; P P >0.05). The skewness of systolic BP increased in space (0.74±0.51 versus 1.43±1.00; P =0.001), indicating that signal fluctuations became asymmetrical; however, it returned to preflight levels after landing (0.51±0.42). The kurtosis increased in space (5.01±7.67 versus 11.10±11.79; P =0.010), suggesting that fluctuations concentrated around the mean with a narrow distribution; however, it also returned to preflight levels (2.21±2.56) after return to earth. Conclusions: Given current countermeasures including in-flight exercise training and volume resuscitation on return, no astronauts experienced orthostatic hypotension or intolerance during routine (for landing day) activities in the initial 24 hours after landing following 6 months in space. Prolonged exposure to spaceflight had little impact on systolic BP variability and its distribution, although the latter showed a transient change in space (accompanied by mild relative hypotension), all of which returned to preflight values after return to earth.

PURPOSE To evaluate postural symmetry in sitting and standing for children with hemiplegic cerebral palsy (hCP) following the Combined Approach to Treatment for Children with Hemiplegia (CATCH) protocol, an intervention combining Constraint Induced Movement Therapy, Bimanual Intensive Therapy and Neuro-Developmental Treatment. METHODS The study included 10 children with a diagnosis of hCP and 10 typically developing age-matched peers. Subjects participated in a CATCH camp for six hours daily for eight consecutive days. Postural symmetry measurements in quiet sitting and standing were obtained using a Boditrak pressure-mapping system at four time points: prior to start of camp (T1), first day of camp (T2), last day of camp (T3), and one month post-camp (T4). RESULTS Significant differences (p< 0.05) were found in quiet sitting when comparing postural symmetry pre-intervention and one-month post camp. In quiet standing, significant differences (p< 0.05) were found when pre-intervention was compared to one-month post-intervention. One month post-intervention, the intervention group showed no significant difference from the comparison group. CONCLUSIONS Children with hCP demonstrate improvement in postural symmetry in sitting and standing following participation in a CATCH camp. Following the intervention, children with hCP continued to improve postural symmetry and approach age-matched peers.

Body sway has usually been studied during symmetrical standing while lower limbs equally contributed in upright posture. The present study aimed to examine the dynamics of body sway while turning during standing with symmetrical and asymmetrical weight distribution between the legs. Subjects performed a body turn of 30° to the right and left during quiet standing and standing with the right or left foot loaded with 70% of body weight. We found that body turn in the symmetrical posture induced weight increase on the foot contralateral to the turning direction and the common center of pressure (COP) velocity increase. Body turn in the asymmetrical posture induced further loading of the foot that was initially overloaded; also turning in the direction of the unloaded foot affects weight distribution more than turning in the direction of the overloaded foot. The posture transition from symmetrical to asymmetrical induced the common COP velocity increase and forward protraction of the unloaded foot COP. Turning in the asymmetrical posture produced further increase of the common COP velocity and further forward protraction of the unloaded foot COP. Moreover, when the left leg was unloaded this resulted not only in left leg's COP forward, but also in left leg's COP lateral protraction, and left leg's COP frontal velocity increase. These findings reveal that body position and weight distribution between the feet interact to stabilize upright posture and show the effect of footedness during turning in asymmetrical standing.

The details on how the position of balance examination is achieved (preceding movement) and what is happening after (subsequent movement) is scarce. We hypothesised that the postural sway in quiet standing can differ due to demanded stability or mobility associated with the preceding and subsequent action. The body sway will be lower with high stability demand task than a condition with high mobility task. Thirteen female ballet students were examined (aged 15.1 ± 0.95 years). Participants were examined in the single-legged standing position as a part of gait initiation (G-I, high mobility) and termination (G-T, high stability) task with the use of force plate. The following Centre of Pressure (COP) variables were analysed: range and standard deviation of COP position, mean COP velocity for AP (anterio-posterior) and ML (medio-lateral) planes. The results showed that for ML plane, body sway was larger for G-I than G-T task. The lowest values of all variables in AP plane (except the COP range) were for G-T task. This difference, confirm our hypothesis, where this difference is not caused by the skills of the participants, but due to the measuring procedure and motor behaviour before and after achieving the measurement position. Our conclusion is limited to the specific posture and homogenous participants.

Background:Balance skills are challenged at the roofing worksite by dynamic visual cues in the form of clouds and trees that move with the wind; any instability may result in a fall from height.Aim:To determine if roofers are less susceptible to a dynamic visual surround (moving room) when stationary cues were available, relative to people who do not work in a similar environment.Methods:Forty male adults participated, including young roofers (N=10,26.3 years), middle-aged roofers (N=10,50.6 years), young controls (N=10,26.2 years) and middle-aged controls (N=10,55.1 years). Center of pressure root mean square (APRMS) was assessed during quiet standing and four moving room conditions when stationary cues were:(1)not in place,(2)in the foreground (inside the moving room),(3)in the background (outside the moving room, but still visible) and (4)in the foreground and background. Results:A workgroup by visual cue interaction was observed (p=0.032), where roofers had up to 18% lower APRMS relative to controls when the background references were in place. The interaction effect was independent of age. Interpretation:The roofers were able to suppress visually-induced postural sway when stationary visual cues were present in the background, likely due to the severe consequences for loss of balance when working at height. The suppression was maintained in aging workers.

Made available in DSpace on 2019-10-06T16:08:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação para o Desenvolvimento da UNESP (FUNDUNESP) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Postural control asymmetry is an important aspect of Parkinson's disease (PD) that may be associated with falls. The aim of this study was to compare the postural control asymmetry during postural tasks between fallers and non-fallers in people with PD and neurological healthy age-matched controls (CG). Individuals with idiopathic PD (n = 24) and CG (n = 24) were sub-divided into groups of fallers and non-fallers based on their fall history over the past year. Participants performed blocks of three 30-s trials of quiet standing with feet in a side-by-side and semi-tandem stance position. The center of pressure parameters for each limb were measured and used to calculate the symmetry index. Fallers compared to non-fallers had decreased asymmetry of vertical force in the side-by-side condition. During the tandem-front leg condition, PD non-fallers increased asymmetry of the medial-lateral velocity of sway compared to CG non-fallers. In addition, for the tandem–back leg condition, PD non-fallers increased asymmetry of total displacement and medial-lateral root mean square and mean velocity of sway compared to PD fallers. The results of the study did not support the hypothesis that PD fallers are more asymmetric than PD non-fallers. On the contrary, our results indicated that PD non-fallers had higher postural control asymmetry, especially during the more challenging (semi-tandem standing) postural task. São Paulo State University (UNESP) – Campus Bauru Graduate Program in Movement Science Human Movement Research Laboratory (MOVI-LAB) Department of Physical Education University of British Columbia School of Kinesiology São Paulo State University (UNESP) – Campus Rio Claro Graduate Program in Movement Science Posture and Gait Studies Laboratory (LEPLO) Department of Physical Education São Paulo State University (UNESP) – Campus Bauru Graduate Program in Movement Science Human Movement Research Laboratory (MOVI-LAB) Department of Physical Education São Paulo State University (UNESP) – Campus Rio Claro Graduate Program in Movement Science Posture and Gait Studies Laboratory (LEPLO) Department of Physical Education FUNDUNESP: 0716/011 FAPESP: 2012/24040-9 FAPESP: 2013/00925-4

Background The use of high-heeled shoes (HHS) introduces instability into the wearer’s balance system but how high-heel experience might influence standing balance is less examined in literature. Research question (1) Does foot stability decrease in both the antero-posterior (AP) and medial-lateral (ML) directions with increasing heel height during quiet standing? (2) Does high-heel experience improve the wearer’s foot stability during quiet standing in high-heeled conditions? Methods Twenty-four young females (12 regular and 12 non-regular HHS wearers) were recruited to perform quiet standing while wearing shoes with heel heights of 1 cm, 5 cm, 8 cm and 10 cm. The effects of heel height on the mean center of pressure (COP), their variability (standard deviations) and mean COP velocities in both the AP and ML directions were analysed by one-way repeated measures ANOVA and Bonferroni post-hoc test. The effects of high-heel experience were analysed through independent samples t-tests. Results The variability of the COP in both directions increased with heel height, although significance was found only in the ML direction. The COP velocities in both directions were highest for the 1 cm heel, decreased as the heel increased to 8 cm and increased again for the 10 cm heel. Experienced HHS wearers exhibited significantly smaller COP variances (AP) for the 8 cm and 10 cm heels, smaller COP velocities (AP) for all heels, and smaller COP variances (ML) and COP velocities (ML) for the 10 cm heel. Significance The use of HHS results in greater stability distortions in both AP and ML directions but high-heel experience improves balance control under high-heeled conditions. Our findings enhance the understanding of how high-heel experience might influence standing balance in different heel height, and highlights the importance of the ML components of the in-foot COP measures in the examination of standing balance in HHS.

Improving stability of people wearing a lower extremity Wearable Exoskeleton (WE) is one of the biggest challenges in the field. The goal of this preliminary study was to improve balance recovery from perturbations in people with incomplete Spinal Cord Injury (SCI) assisted by a WE with specifically developed balance controller. The WE has actuated ankle and knee joints, which were controlled by using a body sway-based balance controller. Two test pilots participated in 5 training sessions, devoted to enhance the use of the robot, and in pre/post assessments. Their balance during quiet standing was perturbed through pushes in forward direction. The controller was effective in supporting balance recovery in both tests pilots as reflected by a smaller sway amplitude and recovery time when compared with a minimal impedance controller. Moreover, the training resulted in a further reduction of the sway amplitude and recovery time in one of the test pilots whereas it had not an additional beneficial effect for the other subject. In conclusion, the novel balance controller can effectively assist people with incomplete SCI in maintaining standing balance and a dedicated training has the potential to further improve balance.

[Purpose] Sports activity has been shown to improve postural stability and vestibular function in healthy older adults. The hypothesis was that healthy young adults undertaking sports activity will also have better postural stability and vestibular function compared with healthy young adults who do not undertake sports activity. The purpose of this study was to investigate the differences in postural stability and vestibular function between healthy young adults who undertake sports activity and those who do not undertake such activity. [Participants and Methods] Thirty-nine healthy young adults were recruited and divided into sports and non-sports groups on the basis of their response to a questionnaire concerning regular participation in sports activities over the past 12 months. In both groups, postural stability was measured during quiet standing and standing during head rotation, and dynamic visual acuity was assessed during head rotation. [Results] The results showed significant differences in postural stability during head rotation and dynamic visual acuity between the two groups, whereas no significant differences were found in postural stability during quiet standing. [Conclusion] The results suggest that healthy young adults who undertake sports activity have better postural stability during head rotation and better dynamic visual acuity. The causal effect of these differences is not clear and further investigation is warranted.

This interview discusses the infinity of stories as an endless reservoir of imagining new forms of meaning, feeling and embodiment of fieldwork data. Thinking of ethnographic analysis and experience as a collaborative process of performance and creative expression is an alternative to the prevailing textocentric documentation that demands both a political economy of contexts and an ethics of loving attention.

Quiet standing exhibits strongly intermittent variability that has inspired at least two interpretations. First, variability can be intermittent through the alternating engagement and disengagement of complementary control processes at distinct scales. A second and perhaps deeper way to interpret this intermittency is through the possibility that postural control depends on cascade-like interactions across many timescales at once, suggesting specific non-Gaussian distributional properties at different timescales. Multiscale probability density function (PDF) analysis shows that quiet standing on a stable surface exhibits a crossover from low, increasing non-Gaussianity (consistent with exponential distributions) at shorter timescales, reflecting inertial control, towards higher non-Gaussianity. Feedback-based control at medium to longer timescales yields a linear decrease characteristic of cascade dynamics. Destabilizing quiet standing with unstable surface or closed eyes serves to attenuate inertial control and to elicit more of the feedback-based control over progressively shorter timescales. The result was to strengthen the appearance of the linear decay indicating cascade dynamics. Finally, both linear and nonlinear indices of postural sway also govern the relative strength of crossover or of linear decay, suggesting that tempering of non-Gaussianity across log-timescale is a function of both extrinsic constraints and endogenous postural control. These results provide new evidence that cascading interactions across longer-timescales supporting postural corrections can even recruit shorter-timescale processes with novel task constraints that can destabilize posture.

Postural sway is a result of a complex action-reaction feedback mechanism generated by the interplay between the environment, the sensory perception, the neural system and the musculation. Postural oscillations are complex, possibly even chaotic. Therefore fitting deterministic models on measured time signals is ambiguous. Here we analyse the response to large enough perturbations during quiet standing such that the resulting responses can clearly be distinguished from the local postural sway. Measurements show that typical responses very closely resemble those of a critically damped oscillator. The recovery dynamics is modelled by an inverted pendulum subject to delayed state feedback and is described in the space of the control parameters. We hypothesize that the control gains are tuned such that (H1) the response is at the border of oscillatory and nonoscillatory motion; (H2) the response is the fastest possible; (H3) the response is a result of a combined optimization of fast response and robustness to sensory perturbations. Parameter fitting shows that H1 and H3 are accepted while H2 is rejected. Thus, the responses of human postural balance to “large” perturbations matches a delayed feedback mechanism that is optimized for a combination of performance and robustness.

Background Studies on short-term upright quiet standing tasks have presented contradictory findings about postural control in people with Parkinson’s disease (pwPD). Prolonged trial durations might better depict body sway and discriminate pwPD and controls. Objective The aim of this study was to investigate postural control in pwPD during a prolonged standing task. Methods A total of 26 pwPD and 25 neurologically healthy individuals performed 3 quiet standing trials (60 s) before completing a constrained prolonged standing task for 15 minutes. Motion capture was used to record body sway (Vicon, 100 Hz). To investigate the body sway behavior during the 15 minutes of standing, the analysis was divided into three 5-minute-long phases: early, middle, and late. The following body sway parameters were calculated for the anterior-posterior (AP) and medial-lateral (ML) directions: velocity, root-mean-square, and detrended fluctuations analysis (DFA). The body sway area was also calculated. Two-way ANOVAs (group and phases) and 1-way ANOVA (group) were used to compare these parameters for the prolonged standing and quiet standing, respectively. Results pwPD presented smaller sway area ( P < .001), less complexity (DFA; AP: P < .009; ML: P < .01), and faster velocity (AP: P < .002; ML: P < .001) of body sway compared with the control group during the prolonged standing task. Although the groups swayed similarly (no difference for sway area) during quiet standing, they presented differences in sway area during the prolonged standing task ( P < .001). Conclusions Prolonged standing task reduced adaptability of the postural control system in pwPD. In addition, the prolonged standing task may better analyze the adaptability of the postural control system in pwPD.

Postural sway refers to the fluctuations in the horizontal movements of the center of mass (COM) while a human stands quietly. The fluctuations in the center of pressure (COP) measured with a force platform provide a measure of the neuromuscular response to the motions of the COM.

As the largest extant legged animals, elephants arguably face the most extreme challenge for stable standing. In this study, we investigated the displacement of the centre of pressure of 12 elephants during quiet standing. We found that the average amplitude of the oscillations in the lateral and fore–aft directions was less than 1.5 cm. Such amplitudes for postural oscillation are comparable with those of dogs and other species, suggesting that some aspects of sensorimotor postural control do not scale with size.

In this study, we investigated the fluctuation characteristics of micro vertical acceleration of center of mass (vCOMacc) in standing and examined the usefulness of vCOMacc as an aging marker for standing control abilities. Sixteen young and 18 older adults participated in this experiment. Data for vCOMacc were calculated as the vertical ground reaction force value divided by each participant&rsquo, s body mass using a force plate. The COMacc frequency structure was determined using the continuous wavelet transform to analyze the relative frequency characteristics. For time domain analysis, we determined the root mean square (RMS) and maximum amplitude (MA) of the integrated power spectral density. We also analyzed the correlation between vCOMacc and lower limb muscle activity. The relative frequency band of vCOMacc was higher in older than young adults, and the time domain indicators were sufficient to distinguish the effects of aging. Regarding the relationship between vCOMacc during standing and muscle activity, a correlation was found with the soleus muscle in young adults, while it was moderately correlated with the gastrocnemius muscle in older adults. The cause of vCOM may be related to differences in muscle activity, and vCOMacc may be utilized to more easily assess the effects of aging in standing control.

We assessed 168 patients with multiple sclerosis (MS) by force platform to obtain the dual-task cost (DTC) of balance, that is, the change in postural sway from quiet standing to dual-task condition (Stroop test). After a median follow-up time of 3.5 years from this assessment, disability progression occurred in 45 (27%) patients. Disability progression was predicted by the adoption of a ‘posture second’ strategy, that is, values of DTC of balance exceeding those obtained from 62 healthy controls, even after controlling by demographic and clinical characteristics. The DTC of balance may potentially represent a novel and easy tool to predict MS progression.

Methods used to assess quiet standing in unilateral prosthesis users often assume validity of an inverted pendulum model despite this being shown as invalid in some instances. The aim of the current study was to evaluate the validity of a proposed unilaterally-constrained pin-controller model in explaining postural control in unilateral prosthesis users. Prosthesis users were contrasted against the theoretical model as were able-bodied controls that stood on a platform which unilaterally constrained movement of the CoP. All participants completed bouts of quiet standing with eyes open, eyes closed and with feedback on inter-limb weight bearing asymmetry. Correlation coefficients were used to infer inverted pendulum behavior in both the anteroposterior and mediolateral directions and were derived from both kinematic (body attached markers) and kinetic (centre of pressure) experimental data. Larger, negative correlation coefficients reflected better model adherence, whilst low or no correlation reflected poorer model adherence. Inverted pendulum behavior derived from kinematic data, indicated coefficients of high magnitude in both mediolateral (all cases range 0.71–0.78) and anteroposterior (0.88–0.91) directions, irrespective of groups. Inverted pendulum behavior derived from kinetic data in the anteroposterior direction indicated validity of the model with large negative coefficients associated with the unconstrained/intact limbs (prosthesis users: − 0.45 to − 0.65, control group: − 0.43 to − 0.72), small coefficients in constrained/prosthetic limbs (prosthesis users: − 0.02 to 0.07, control group: 0.13–0.26) and large negative coefficients in combined conditions (prosthesis users: − 0.36 to − 0.56, control group: − 0.71 to − 0.82). For the mediolateral direction, coefficients were negligible for individual limbs (0.03–0.17) and moderate to large negative correlations, irrespective of group (− 0.31 to − 0.73). Data suggested both prosthesis users’ and able-bodied individuals’ postural control conforms well to that predicted by a unilaterally-constrained pin-controller model, which has implications for the fundamental control of posture in transtibial prosthesis users.

A cross-sectional, prospective, between-subjects design was used in this study to establish the differences in sensory reweighting of postural control among different ages during adolescence. A total of 153 adolescents (five age groups; 13–17 years old) performed bipedal standing in three sensory conditions (i.e., with visual restriction, vestibular disturbance, and proprioceptive disturbance). Center of pressure displacement signals were measured in mediolateral and anteroposterior directions to characterize reweighting in the sensory system in static postural control when sensory information is disturbed or restricted during adolescent growth. The results indicate a development of postural control, showing large differences between subjects of 13–14 years old and older adolescents. A critical change was found in sensory reweighting during bipedal stance with disturbance of proprioceptive information at 15 years old. Adolescents of 13–14 years old showed less postural control and performance than older adolescents during the disturbance of proprioceptive information. Moreover, the results demonstrated that the visual system achieves its development around 15–16 years old. In conclusion, this research suggests that a difference of sensory reweighting under this type of sensorial condition and sensory reweight systems would seem to achieve stabilization at the age of 15.

Plantarflexors such as the soleus (SOL) and medial gastrocnemius (MG) play key roles in controlling bipedal stance; however, how the central nervous system controls the activation levels of these plantarflexors is not well understood. Here we investigated how the central nervous system controls the plantarflexors’ activation level during quiet standing in a cosine tuning manner where the maximal activation is achieved in a preferred direction (PD). Furthermore, we investigated how spinal cord injury affects these plantarflexors’ activations. Thirteen healthy adults (AB) and thirteen individuals with chronic, incomplete spinal cord injury (iSCI) performed quiet standing trials. Their body kinematics and kinetics as well as electromyography signals from the MG and SOL were recorded. In the AB group, we found that the plantarflexors followed the cosine tuning manner during quiet standing. That is, MG was most active when the ratio of plantarflexion torque to knee extension torque was ~2:-3, whereas SOL was most active when the ratio was ~2:1. This suggests that the SOL muscle, despite being a monoarticular muscle, is sensitive to both ankle plantarflexion and knee extension during quiet standing. The difference in the PDs accounts for the phasic activity of MG and for the tonic activity of SOL. Unlike the AB group, the MG’s activity was similar to the SOL’s activity in the iSCI group, and the SOL PDs were similar to those in the AB group. This result suggests that chronic iSCI affects the control strategy, i.e., cosine tuning, for MG, which may affect standing balance in individuals with iSCI. NEW & NOTEWORTHY Soleus muscle shows a tonic activity whereas medial gastrocnemius muscle shows a phasic activity during quiet standing. Cosine tuning and their preferred direction account for the different muscle activation patterns between these two muscles. In individuals with chronic incomplete spinal cord injury, the preferred direction of gastrocnemius medial head is affected, which may result in their deteriorated standing balance.

Background: The aim of this study was to investigate differences in static and dynamic plantar pressure and other foot geometry variables between female Olympic-style weightlifters and an age- and sex-matched control group. Methods: The study involved 24 national-level competitive weightlifters and 24 physical education students. Leg dominance was determined and baropodometry was used to assess plantar pressure and foot posture during quiet standing and walking. For all variables basic descriptive statistics were calculated (mean &plusmn, standard deviation). Student&rsquo, s t test was used to compare the between-group differences. Spearman&rsquo, s rank correlation coefficients were calculated to determine the association between BMI (Body Mass Index) and average and peak plantar pressure. Results: No significant differences were observed in plantar pressure distribution between the two groups. A moderate correlation was found between BMI and non-dominant limb peak and average plantar pressure in the group of weightlifters in the static condition and in the control group in the dynamic condition. Conclusions: Olympic-style weightlifting may affect plantar pressure distribution and foot posture in female weightlifters. BMI may also correlate with peak and average plantar pressure in this population. Further research is needed to determine if Olympic-style weightlifting may affect plantar pressure distribution and foot posture in female weightlifters.

[Purpose] To examine the influence of dorsolateral prefrontal cortex (DLPFC) activation, ankle muscle activities, and coactivation on postural steadiness during dual-tasks. [Participants and Methods] A total of 14 participants (8 males, 6 females) were included. The participants stood straight on the force plate, and performed 3 different tasks: 1) a quiet standing (single-task), 2) a repetition of a number (dual-task 1: DT1), and 3) a serial subtraction (dual-task 2: DT2). We divided the participants into 2 groups (S and L group) according to whether their center of pressure paths in the dual-tasks were shorter or longer than those in the single-task. The EMG activity of the gastrocnemius lateralis and tibialis anterior were measured; the oxygenated hemoglobin (oxy-Hb) level in the DLPFC were measured using fNIRS. [Results] The results revealed that oxy-Hb in the left DLPFC increased significantly in all participants during DT2 compared to a single-task. Further, we found that the S group exhibited a higher rate of tibialis anterior activity and ankle muscle coactivation than the L group during DT2. [Conclusion] We concluded that the increase of the DLPFC activation varied with the dual-tasks; moreover, younger individuals modulate their standing posture using different strategies for posture steadiness during posture-calculating task.

Fall risk is a serious problem especially for the elderly. Fall accident causes fracture, and it leads to bedridden. Early detection of balance inability and rehabilitation training is important to decrease the risk. Quiet standing test is one of the physical tests to assess the balance inability of human. When the human is standing, he/she controls the plantar force to keep the balance. Center of pressure (COP) is the representative parameter to explain the plantar force movement. During the quiet standing test, COP fluctuates unconsciously. There are many researches that analyze the relationship between the COP fluctuation and balance inability. Many statistical indicators have been developed to assess the fluctuation specification.In contrast, several researchers have been tried to reveal the COP fluctuation mechanism by introducing stochastic mathematical model. Ornstein-Uhlenbeck process and diffusion equation are often introduced to the model. The mathematical models have been developed, and analyzed how visual input is related to the model parameters. If the mathematical model can explain the COP fluctuation completely, it becomes easier to assess the balance ability by comparing the model parameters.However, statistical indicators are still used in the clinical cases, thus there is room to discuss which statistical indicators to be used for assessment. The purpose of this research is to explore the relationship between statistical indicators and numerical model by evaluating whether the numerical model reproduces the same values with real data. The reproduced indicators and original indicators are compared, and the magnitude of the errors are evaluated.