Mediolateral Displacement Research Articles

Use of an inertial sensor and a force platform to assess static balance in participants affected by multibacillary leprosy.

Leprosy is a chronic, slowly developing infectious disease that affects the peripheral nerves, specifically Schwann cells. Individuals with the multibacillary type exhibit a propensity for developing chronic pain and a decrease in sensitivity in the plantar region, which directly interferes with balance maintenance. The evaluation of static balance in this population is made through the measurement of the center of pressure (COP) oscillations. Therefore, there is a need to investigate the association between postural control and COP oscillations using a force platform and finding accelerations of the center of mass (COM) from inertial sensors for reliable and portable balance assessment in leprosy patients. To validate the application of inertial sensors for patients with leprosy by establishing a correlation with the outcomes obtained from a force platform. This is an observational study with a case-control design, in which 30 participants with leprosy and 30 healthy participants were recruited to evaluate static balance using an inertial sensor and a force platform. Participants underwent balance assessment under two conditions (Eyes Open: OE and Eyes Closed: CE), and data from the platform and sensor were processed using Matlab computational routines. The data were quantified using four parameters: Total Displacement (TD), Area, Antero-Posterior Displacement (APdisp), and Medio-Lateral Displacement (MLdisp). The evaluated parameters showed significantly different values between the groups, where the Leprosy group exhibited significantly higher values compared to the control group, both in the OE and CE conditions for all four parameters. The sensor corroborated the differences demonstrated by the platform and followed the same trend for medio-lateral displacements and accelerations. It can be observed that the evaluated parameters exhibited a varied correlation ranging from moderate to large between the platform and the sensor. Among the four variables, MLdisp had the lowest correlation. The results partially confirmed the first hypothesis of concurrent validation, showing a moderate to large correlation between the force platform and the inertial sensor. The second hypothesis of clinical validation was also partially confirmed, as not all group differences observed in the COP measurements from the force platform were reflected in the COM measurements from the inertial sensor. Specifically, the force platform indicated greater oscillations in participants with multibacillary leprosy compared to controls, a finding statistically confirmed by the sensor for all measures except MLdisp. This research confirmed the concurrent validity of the inertial sensor with the force platform and its clinical validation, demonstrating that this instrument can be applied in clinical settings due to its low cost and ease of use. The findings may contribute to public health by identifying postural control tools for patients with multibacillary leprosy.

Effects of mediolateral whole-body vibration during gait with additional cognitive load

Whole-body vibration (WBV) may increase musculoskeletal disorder risk among workers standing on vibrating surfaces for prolonged periods. Limited studies were conducted to comprehend WBV impact on individuals engaged in dynamic activities. This study explored the effects of different horizontal WBV frequencies on gait parameters, lower limb kinematics, and the cognitive response of healthy subjects. Forty participants walked at constant speed on a treadmill mounted on a horizontal shaker providing harmonic vibration with an amplitude of 1 m/s2 and frequencies 2–10 Hz, with inversely proportional amplitudes. A Psychomotor Vigilance Test measured reaction time while a motion capture system recorded walking kinematics. ANOVA results revealed no significant impact of vibration frequencies on the reaction time. At 2 Hz, alterations in gait spatiotemporal parameters were significant, with reduced stride length, stride time, step length, and stance time and increased step width and cadence. Similarly, gait variability measured by standard deviation and coefficient of variation significantly increased at 2 Hz compared to the other conditions. Comparably, kinematic time series analyzed through statistical parametric mapping showed significant adjustments in different portions of the gait cycle at 2 Hz, including increased hip abduction and flexion, greater knee flexion around the heel strike, and augmented ankle dorsiflexion. Participants exhibited gait kinematic variations, mainly at 2 Hz, where the associated mediolateral displacement was higher, as a plausible strategy to maintain stability and postural control during perturbed locomotion. These findings highlight individuals’ complex biomechanical adaptations in response to horizontal WBV, especially at lower frequencies, under dual-task conditions.

The Fukuda stepping test is associated with various patterns of displacement

Abstract Objective: This study was to characterize individual path trajectories during the 50-step Fukuda stepping test (FST) and to determine the impact of step height on these trajectories. Methods: Kinematic data from the shoulders and feet were recorded in 12 young healthy adults while performing the FST at a comfortable step height (CoStep) and while stepping with lifting the knees high (HiStep). Path trajectories were depicted by step-by-step displacement of the right and left toes, and body rotation was obtained from the rotation of the shoulders. The effect of step height on the distance traveled and the final anteroposterior (AP) and mediolateral displacements and rotation were determined with paired t-tests. Results: Path trajectories were composed of various combinations of forward displacement, lateral deviation, and rotation to the left or right. In comparison with CoStep, the mean AP displacement and mean distance traveled were significantly shorter in HiStep (P < 0.05) while the mean rotation was significantly larger in HiStep (P < 0.05), but the displacement patterns were not modified. Conclusion: We found that the path trajectories vary greatly among participants, and that step height has a significant impact on the magnitude of displacements and rotation during the FST.

Dynamics of Center of Pressure Trajectory in Gait: Unilateral Transfemoral Amputees Versus Non-Disabled Individuals.

The primary goal of rehabilitation for individuals with lower limb amputation, particularly those with unilateral transfemoral amputation (uTFA), is to restore their ability to walk independently. Effective control of the center of pressure (COP) during gait is vital for maintaining balance and stability, yet it poses a significant challenge for individuals with uTFA. This study aims to study the COP during gait in individuals with uTFA and elucidate their unique compensatory strategies. This study involved 12 uTFA participants and age-matched non-disabled controls, with gait and COP trajectory data collected using an instrumented treadmill. Gait and COP parameters between the control limb (CL), prosthetic limb (PL), and intact limb (IL) were compared. Notably, the mediolateral displacement of COP in PL exhibited significant lateral displacement compared to the CL from 30% to 60% of the stance. In 20% to 45% of the stance, the COP forward speed of PL was significantly higher than that of the IL. Furthermore, during the initial 20% of the stance, the vertical ground reaction force of PL was significantly lower than that of IL. Additionally, individuals with uTFA exhibited a distinct gait pattern with altered duration of loading response, single limb support, pre-swing and swing phases, and step time. These findings indicate the adaptability of individuals with uTFA in weight transfer, balance control, and pressure distribution on gait stability. In conclusion, this study provides valuable insights into the unique gait dynamics and balance strategies of uTFA patients, highlighting the importance of optimizing prosthetic design, alignment procedures, and rehabilitation programs to enhance gait patterns and reduce the risk of injuries due to compensatory movements.

Combining Vestibular Rehabilitation and Noisy Galvanic Vestibular Stimulation for Treatment of Unilateral Vestibulopathy: A Randomized Controlled Trial

Background and Aim: Vestibular Rehabilitation (VR) is a well-accepted treatment for Unilateral Vestibulopathy (UVP). Since noisy Galvanic Vestibular Stimulation (nGVS) improves the processing of vestibular inputs, we assessed the synergistic effects of adding nGVS to vestibular rehabilitation for the treatment of UVP. Methods: Patients with UVP were randomly assigned into two groups receiving either VR for four weeks (VR group, n=12) or VR for four weeks combined with nGVS for three sessions (VR+nGVS group; n=12). Outcome measurements were postural control parameters measured with eyes open/closed conditions on hard/soft surfaces, Vestibulo-Ocular Reflex (VOR) gain, and Dizziness Handicap Inventory (DHI) scores that were assessed at baseline and after four weeks. Results: All postural control parameters, mean total and subscale scores of DHI, and mean VOR gain in directions of affected canals significantly improved in both groups after interventions (p<0.05) except mean mediolateral displacement in conditions with eyes closed on hard surface and with eyes open on soft surface, mean mediolateral velocity in conditions with eyes closed on hard surface, ability to stance with eye closed condition on soft surface and mean emotional subscale of DHI in VR group. Improvements were significantly higher in postural control outcomes measured in stances with eyes closed on hard surface and with eyes open and closed on soft surface, mean VOR gains in directions of affected horizontal and anterior canals, and mean total, physical, and functional scores of DHI in VR+nGVS group (p<0.05). Conclusion: When combined with VR, nGVS shows additional therapeutic effects in UVP patients. Keywords: Unilateral peripheral vestibulopathy; vestibular compensation; galvanic vestibular stimulation; vestibular rehabilitation; postural control

Postural Responses to Achilles Tendon Vibration Depend on Feet Positioning.

Mechanical vibration of the Achilles tendon is widely used to analyze the role of proprioception in postural control. The response to this tendon vibration (TV) has been analyzed in the upright posture, but the feet positions have varied in past research. Moreover, investigators have addressed only temporal parameters of the center of pressure (CoP). We investigated the effect of TV on both temporal and spectral characteristics of the CoP motion. Eighteen healthy young adults, stood barefoot, with one foot on each side of a dual platform, wearing glasses with opaque lenses. We applied 20seconds of Achilles TV (bilaterally with inertial vibrators at a frequency of 80Hz and an amplitude of .2-.5mm). We analyzed CoP signals pre-vibration (PRE,4-seconds), during vibration (VIB,20 seconds), and after vibration cessation (REC,20 seconds). We repeated this protocol in natural and standardized positions (15° feet angular opening). For determining CoP amplitude and velocity, we divided the 20seconds into five phases of fourseconds each and calculated spectral parameters for the whole 20-second signals. There was an adaptation process in the speed of the CoP mediolateral (p < .01) and anteroposterior (p < .01) and in the displacement of the CoP anteroposterior (p < .01), with higher values in the VIB condition. Velocity and displacement decreased progressively in the REC condition. Median and peak frequencies were higher in the VIB condition when compared to the REC condition, but only in the mediolateral direction (p = .01). The standardized foot position led to increased speed in CoP mediolateral, anteroposterior, and mediolateral displacement (p < .01). CoP spectral characteristics were not affected by foot positioning. We concluded that adaptation of CoP motion in the presence of TV and after its cessation are observable both in time and frequency domains. Feet positioning influenced CoP motion in the presence of TV and after its cessation but it did not affect its spectral characteristics.

Kinematics of lateral tongue-pushing movement in coordination with masticatory jaw movement: An anteroposterior projection videofluorographic study

ObjectiveDuring the mastication of solid food, the tongue pushes the bolus laterally to place it onto occlusal surfaces as the jaw is opened. This movement is referred to as tongue-pushing (TP). TP has an important role in efficient chewing, but its kinematic mechanisms remain unclear. The present study quantified the kinematics of TP and its coordination with masticatory jaw movements. MethodsVideofluorography (VFG) in anteroposterior projection was recorded while 14 healthy young adults ate 6 g each of cookies and meat. Small lead markers were glued to the tongue surface (left, right, and anterior) and buccal tooth surfaces (upper molars and lower canines). The position of the tongue and lower canine markers relative to the upper occlusal plane was quantified with Cartesian coordinates, using the right upper molar as the origin. Jaw motion during chewing was divided into TP and Non-TP cycles, based on the lateral movement of the food and tongue markers. The side of the jaw that compressed food particles was defined as the working side, while the other side was termed the balancing side. Horizontal and vertical displacements of tongue and jaw markers were compared between TP and Non-TP cycles, as well as between food types. ResultsThe mediolateral displacement of all tongue markers was significantly larger in TP than in Non-TP cycles. Vertical displacement was also significantly greater in TP than in Non-TP cycles for the anterior and working side tongue markers. TP cycles occurred more frequently with meat-chewing than with cookie-chewing. ConclusionTP is accomplished by rotation and lateral movements of the tongue surface on the working side and the anterior tongue blade, along with medial movement on the balancing side. These movements produce lateral shift and rotation of the tongue surface toward the working side in concert with jaw opening. Designing exercises to improve the strength of the lateral motion and rotation of the tongue body may be useful for individuals with impaired tongue function for eating and swallowing.

Can a rigid antipronation foot orthosis change the effects of prolonged standing on postural control in men with patellofemoral pain?

Pronated foot posture is known as a contributing factor for patellofemoral pain (PFP) development. Patients with patellofemoral pain often experience poor postural control. Implementation of optimal management strategies for enhancing their postural performance is important. The aim of this study was to determine whether a rigid antipronation foot orthosis changes prolonged standing effects on postural control in men with PFP. Case-control study. Twenty-eight men with PFP and pronated foot and 28 healthy men were enrolled in this study. Center-of-pressure parameters were measured during short trials (60 seconds) of single-leg standing before and immediately after prolonged standing (20 minutes) using force platform. In patients with PFP, postural control was examined on 2 separate days with and without rigid antipronation foot orthosis. Findings showed that the pre-post differences of sway area (t(48) = -2.22, p = 0.03), mediolateral (ML) displacement (t (48) = -2.51, p = 0.01), and mean velocity (t(48) = -2.01, p = 0.04) were significantly greater in patients with PFP without foot orthosis compared with those in the healthy group. Significant intervention main effect ( p = 0.04) and time-by-intervention interaction ( p = 0.006) for sway area were shown. Significant intervention main effects were noted for ML displacement ( p = 0.007) and mean velocity ( p = 0.003). For these variables, significant time-by-intervention interactions were found. Further analysis showed greater values of ML displacement and mean velocity parameters before the prolonged standing in patients with PFP without foot orthosis compared with patients with PFP with orthosis. Rigid antipronation foot orthosis can improve the postural performance after prolonged standing in young adult men with PFP.

Gluteus medius muscle strengthening exercise effects on medial longitudinal arch height in individuals with flexible flatfoot: a randomized controlled trial.

This study aimed to compare the effects of 8 weeks of foot plus hip exercise to foot exercise alone on medial longitudinal arch (MLA) parameters; navicular drop (ND), arch height index (AHI), plantar pressure, static balance, and dynamic balance were measured at baseline, 4 weeks, and 8 weeks. A total of 52 healthy participants with bilateral flatfoot were randomly assigned into foot exercise (n=26) and foot plus hip exercise (n=26) group. At 4 weeks, the foot plus hip exercise group showed significantly less ND (P=0.002), plantar pressure at the medial forefoot (P=0.002), and mediolateral displacement (P=0.001) while showing a greater AHI (P=0.019) than the foot exercise group. At 8 weeks, there was also significantly less plantar pressure at the medial hindfoot (P=0.017) and less anteroposterior displacement (P=0.002) in the foot plus hip exercise group than in the foot exercise group. No significant differences between groups were found in dynamic balance. The addition of gluteus medius muscle strengthening exercise to foot exercise was more effective in supporting the MLA than performing foot exercise alone.

Using Wearable Inertial Sensors to Monitor Effectiveness of Different Types of Customized Orthoses during CrossFit® Training.

Dynamic balance plays a key role in high-impact sports, such as CrossFit, where athletes are required to maintain balance in various weightlifting exercises. The loss of balance in these sport-specific movements may not only affect athlete performance, but also increase the risk of injuries. The aim of the study is to achieve greater insight into the balance and athlete position during the CrossFit training by means of inertial sensors, with a particular focus on the role of different custom foot orthoses (CFOs) in order to detect correlations with the role of the cavus foot. A total of 42 CrossFit® athletes, aged 25 to 42 years, were enrolled in this study. One-way ANOVA tests with post-hoc analysis of variance were used to compare foot posture groups and effects of different types of customized foot orthoses. When comparing the effects of CFOs with the respective balance basal level during the pistol squat exercise, we observed a significant (p = 0.0001) decrease in the sway area, antero-posterior displacement (APD) and medio-lateral displacement (MLD) compared to the basal using both types of CFOs. No significant positive effects of CFOs were observed in some static tests. On the contrary, positive effects of CFOs and, in particular, postural insoles, are relevant to dynamic balance.

The Patellostabilometer: A New Device for Quantification of Mediolateral Patella Displacement.

Mediolateral patella displacement is of interest for diagnostics and clinically relevant research questions. Apart from manual testing, no standardized method is currently available. Proper quantification of patella mobility is necessary to better understand pathologies at the patellofemoral joint. Patella mobility was assessed in 25 healthy individuals using a Patellostabilometer, a new prototype instrument for quantification of the mediolateral patella displacement. The participants underwent measurements of the mediolateral displacement three times using the Patellostabilometer. A maximal force of 10 N was applied for patella movement. Additionally, leg length and circumference of the knee, upper- and lower-leg were measured. Lateral patella displacement of 18.27 ± 3.76 mm (range 15.85-20.64 mm, interquartile range (IQR) of 4.79) was measured. The medial patella displacement showed 24.47 ± 6.59 mm (range 19.29-29.76 mm, IQR of 10.47). The test-retest measurement error was 2.32 ± 1.76 mm (IQR of 2.38 mm), with five outliers. There was greater test-retest variability between the measurements of the medial displacement compared to the lateral one. The test-retest variability reached 7% of the patella displacement. Other parameters provided no significant correlations. Based on the natural patellofemoral mobility, a precise and clinically relevant quantification of patella mobility is allowed.

Effect of Alteration in Hip Joint Alignment following Total Hip Arthroplasty on Hip Joint Contact Force during Gait

Purpose Investigation of the relationship between changes in hip-joint center and hip loading pre- and post- total hip arthroplasty (THA) is important in evaluating the effect of surgery on motor function. However, few longitudinal studies comparing pre- and post-THA have been reported. The purpose of this study was to determine the effect of changes in hip-joint center pre- and post-THA on the magnitude and direction of hip-joint contact force during the gait cycle, using a patient-specific musculoskeletal model. Methods The simulation program AnyBody was used to create musculoskeletal models incorporating patient specific hip-joint shape and hip-joint center position for 17 patients. The relationship between the displacement distance of the hip-joint center and the amount of change in hip-joint contact force was examined by correlation analysis. Results A decrease in the medial force (p ≤ 0.049) and an increase in the anterior force (p ≤ 0.001) acting on the hip joint were observed during gait post-THA compared to pre-THA. Mediolateral displacement of the hip-joint center post-THA compared to pre-THA was significantly positively correlated with the difference in anterior hip-joint contact force, and negatively to hip-joint medial contact force. Conclusions Longitudinal observations revealed the effects of change in hip-joint center position induced by THA on the hip-joint contact force during gait. Therefore, the change of hip-joint center position during THA can be an important factor for estimating the improvement of motor function following THA.

Trunk Kinematics of Experienced Riders and Novice Riders During Rising Trot on a Riding Simulator

Asymmetry of horses and humans is widely acknowledged, but the influence of one upon the other during horse riding is poorly understood. Riding simulators are popular for education of beginners and analysis of rider biomechanics. This study compares trunk kinematics and saddle forces of 10 experienced riders (ER) and 10 novice riders (NR) performing rising trot on a simulator. Markers were placed on the 4th lumbar (L4) and 7th cervical (C7) spinous processes, and both acromion processes. Displacements in three axes of motion were tracked using 10 high-speed video cameras sampling at 240 Hz. Displacement trajectories at L4 and C7 were similar between both groups, displaying an asymmetrical butterfly pattern in the frontal plane, which reversed when changing diagonal. Comparison between groups, NR displayed greater vertical displacement and higher saddle impact forces at L4 (P = .034), greater amplitude of medio-lateral displacement on the right diagonal between C7 and L4, and on the right diagonal while seated they rotated left (acromion processes) while the ER rotated right. Within group comparison demonstrated that on the right diagonal both groups produced significantly greater medio-lateral displacement at L4, and NR displayed significantly greater medio-lateral displacement between C7 and L4. On the left diagonal NR produced significantly greater vertical displacement and higher saddle impact forces.The findings of this study suggest that ER were more stable, symmetrical, and had lower impact force on the saddle. These issues could be addressed in beginners using a simulator to avoid unnecessary stresses on horses.

The effects of anterior and posterior ankle-foot orthoses on sit-to-stand transfer performance in stroke patients

BackgroundNonarticulated and low-temperature thermoplastic ankle–foot orthoses (AFOs) have a semirigid design and are effective in improving the postural control mechanism (PCM) in individuals with poststroke hemiparesis. AFOs with an anterior leaf (AAFOs) are more often prescribed than are AFOs with a posterior leaf (PAFOs); however, the effects of AAFOs on the PCM during sit-to-stand transfer (STST) have not been explored. Research questionsDo AAFOs and PAFOs change the PCM differently during STST? MethodsA cross-sectional quasi-experimental design was adopted in this study. Fourteen individuals with poststroke hemiparesis (10 men and 4 women, aged between 38 and 71 years, stroke onset between 1 and 17 months) performed STST with shoes only, an AAFO with shoes, or a PAFO with shoes. Vertical ground reaction force (VGRF) and center-of-pressure (CoP) coordinates were collected using a pressure mat to calculate PCM parameters. A single-factor repeated measures analysis of variance was performed to answer the research question. Results(1) The weight-bearing percentage of the paretic leg was significantly lower when the participants wore a PAFO (p = 0.018) than when they wore an AAFO (p = 0.019) during the first 5 and 5–10 s after rising. (2) A small rate of change of the VGRF increment (dF/dT) was detected when participants wore AFOs, particularly AAFO. (3) The maximum mediolateral displacement of the CoP when standing up was significantly different among the three conditions (p = 0.012). SignificanceFor patients with poststroke hemiparesis, AAFO and PAFOs change the PCM during STST performance. Only AAFO improved the PCM possibly because of the rigidity and clearance of the heel region, which provide somatic sensory feedback. Therefore, rehabilitation professionals should educate hemiplegic patients who use AAFOs or PAFOs to perform dynamic daily tasks slowly for their safety.

Fast Saccadic Eye Movements Contribute to the Worsened Postural Sway in Older Adults Who Have Experienced Falls.

The purpose of this study was to examine changes and between-group differences in postural sway during saccadic eye movement in older adults (n = 152). The participants were stratified into older adults who have experienced a fall (n = 58) (faller group) and those who have not (n = 94) (non-faller group). We measured postural sway during saccadic eye movement. Saccadic eye movement speed was such that the target was displayed at 0.5 Hz, 2 Hz, and 3 Hz. Postural sway was measured based on path length, velocity, and length between the maximal and minimal position of center of pressure in mediolateral and anteroposterior direction. In the faller group, path length, velocity, and mediolateral displacement of the center of pressure increased significantly during 3 Hz saccadic eye movement stimulation. However, in the non-faller group, there was no significant change in the center of pressure parameters during saccadic eye movement stimulation. Mediolateral displacement of the center of pressure increased significantly in both groups during saccadic eye movement, especially at 3 Hz. Therefore, rapid saccadic eye movement stimulation can contribute to the worsened postural sway in older adults who have experienced falls, and rapid external environmental stimuli may contribute to the deterioration of the upright standing stability in older adults.

Immediate Effect of Augmented Reality, Virtual Reality, and Neurofunctional Physiotherapy on Postural Control and Executive Function of Individuals with Parkinson's Disease.

Objective: To assess the immediate effect of augmented reality (AR), virtual reality (VR), and neurofunctional physiotherapy (NPT) on postural control (PC) and executive function (EF) of individuals with Parkinson's disease (PD). Materials and Methods: Forty subjects from mild-to-moderate PD stages, with no cognitive impairment were submitted to one session of NPT, one session of AR, and one session of VR for 50 minutes each (7 days interval between them). PC was evaluated before and after each therapy, using force platform in bipedal positions: tandem with eyes opened (EO), eyes closed (EC), and with double-task and one-legged stance. We recorded the center of pressure area, and anteroposterior (AP) and mediolateral (ML) displacement amplitude and velocity. EF was assessed by Trail Making Test (TMT). Results: PC improved (pre- vs. postintervention) after the three modalities: AP velocity decreased after AR (tandem EC 2.3 [1.7 to 2.9] vs. 2.1 [1.5 to 2.9], one-legged 3.0 [1.9 to 4.0] vs. 2.9 [1.9 to 3.6]), NPT (tandem EC 2.2 [1.7 to 3.1] vs. 2.1 [1.6 to 3.0]), and VR (tandem EO 1.9 [1.4 to 2.6] vs. 1.8 [1.4 to 2.4], tandem EC 2.3 [1.6 to 3.0] vs. 2.0 [1.5 to 2.8]); ML velocity decreased after AR in one-legged (P = 0.04); and permanence time in one-legged position increased in AR (Δ: 2.5 [-0.2 to 6.9]). There was also improvement in EF: TMT part A (TMTA)'s time decreased after AR (-9.3 [-15.7 to 1.9]), and TMT part B (TMTB)'s time decreased after the three modalities (ΔNPT: -7.7 [-29.4 to 0.0] vs. ΔAR: -4.6 [-34.6 to 0.6] vs. ΔVR: -4.9 [-28.2 to 0.9]). There were no differences between the modalities. Conclusion: The three treatment modalities improved PC and EF of subjects with PD. Moreover, AR and VR generated similar immediate effects to NPT on both outcomes in these patients. Trial registration: Brazilian Clinical Trial Registration: RBR-5r5dhf.

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.

Three-dimensional front crawl arm-stroke efficiency and hand displacement in male and female swimmers

ABSTRACT This study aimed (i) to verify if underwater horizontal, vertical and medio-lateral hand displacements (HD), in pull and push phases of the front crawl stroke, can be associated with arm-stroke efficiency (ƞp) and (ii) to compare np and selected kinematic variables between male and female swimmers. Ten male and 10 female swimmers performed an all-out front crawl 25-m test. Data were obtained with six synchronised video cameras (60 Hz) and analysed with a three-dimensional method. Results for males and females were respectively, as follows: (i) horizontal HD: 0.55 ± 0.06 m and 0.61 ± 0.09 m (p = 0.062; d = 0.78); vertical HD: 0.68 ± 0.06 m and 0.58 ± 0.07 m (p < 0.001; d = 1.53); and medio-lateral HD: 0.22 ± 0.07 m and 0.16 ± 0.03 m (p = 0.012; d = 1.11); (ii) ƞp: 0.33 ± 0.02 and 0.32 ± 0.03 (p = 0.48; d = 0.39); (iii) vCOM: 1.77 ± 0.06 m∙s−1 and 1.55 ± 0.10 m∙s−1 (p < 0.001; d = 2.42). Multiple linear regression (p = 0.019) indicated that horizontal and medio-lateral HD were able to predict np. The lower the horizontal hand displacement, the higher the ƞp.

Age-dependent perturbation of the perceptual and postural vertical by visual roll vection and susceptibility to motion sickness in children

BackgroundThe visual contribution to the perceptual and postural vertical is mediated by a multisensory integration process and may relate to children’s susceptibility to motion sickness that is hypothesized to arise from intersensory conflicts.ObjectiveTo analyze the maturation of visual contribution to the perceptual and postural vertical in conjunction with the motion sickness susceptibility in childhood.MethodsIn 81 healthy children (aged 2–17 years; 57 females), adjustments of the subjective visual vertical and posturographically tested mediolateral displacements of body sway were measured during free upright stance and large-field visual motion stimulation in the roll plane (roll vection). Motion sickness susceptibility was assessed by taking the history of parents and children.ResultsVection-induced tilts of the visual vertical showed a linear age-dependent decrease with largest tilts in the youngest (2–7 years; median of 20°) and smallest tilts in the oldest age group (13–17 years; median of 9–10°). Analogously, postural tilts as measured by mediolateral body sway were greatest in the youngest and smallest in the oldest age group. In contrast, motion sickness susceptibility was lowest in the youngest and highest in the oldest age group and exhibited an inverse correlation with vection-induced tilts of the visual vertical.ConclusionRoll vection-induced tilts of the visual and postural vertical exhibited a similar age-dependent course with the greatest effects in the youngest and the least effects in the oldest age group, the latter of which exhibited the highest susceptibility to motion sickness.

Changes in postural balance associated with a woman's aging process

ContextAging causes a progressive worsening in postural balance, affecting functional independence and increasing the risk of falls. ObjectiveThe aim of the study was to evaluate the effect of aging on the static balance in women from 50-years to 89-years of age. DesignThis was a cross-sectional study, with 400 irregularly active women were evaluated and grouped by age: Group 6th decade (age 50 to 59) ‒ 58 participants; Group 7th decade (age 60 to 69) ‒ 214 participants; Group 8th decade (age 70 to 79) ‒ 92 participants; Group 9th decade (age 80 to 89) ‒ 36 participants. Postural balance was evaluated using a portable force platform in a standard standing position, with Eyes Open (EO) and Eyes Closed (EC). ResultsIn the two measurement conditions, the elderly women in Group 9th decade presented mediolateral displacement and range, and mean velocity greater than the women's values in Groups 6th and 7th decade. In the EO e EC situation, the displacement was higher in the elderly Group 9th decade compared to younger groups. Group 8th has a mean velocity greater than Group 6th decade in the EO situation. ConclusionsPosturography showed a decline in postural balance with advancing age, suggesting that the 9th decade of life is a borderline age to this detriment due to an increase in postural instability.