Medial-lateral Direction Research Articles

Improved vessel-tissue contrast and image quality in 3D radial sampling-based 4D-MRI.

PurposeIn radiation treatment planning for thoracic and abdominal tumors, 4D‐MRI has shown promise in respiratory motion characterization with improved soft‐tissue contrast compared to clinical standard, 4D computed tomography (4D‐CT). This study aimed to further improve vessel–tissue contrast and overall image quality in 3D radial sampling‐based 4D‐MRI using a slab‐selective (SS) excitation approach.MethodsThe technique was implemented in a 3D radial sampling with self‐gating‐based k‐space sorting sequence. The SS excitation approach was compared to a non‐selective (NS) approach in six cancer patients and two healthy volunteers at 3T. Improvements in vessel–tissue contrast ratio (CR) and vessel signal‐to‐noise ratio (SNR) were analyzed in five of the eight subjects. Image quality was visually assessed in all subjects on a 4‐point scale (0: poor; 3: excellent). Tumor (patients) and pancreas (healthy) motion trajectories were compared between the two imaging approaches.ResultsCompared with NS‐4D‐MRI, SS‐4D‐MRI significantly improved the overall vessel–tissue CR (2.60 ± 3.97 vs. 1.03 ± 1.44, P < 0.05), SNR (63.33 ± 38.45 vs. 35.74 ± 28.59, P < 0.05), and image quality score (2.6 ± 0.5 vs. 1.4 ± 0.5, P = 0.02). Motion trajectories from the two approaches exhibited strong correlation in the superior–inferior (0.96 ± 0.06), but weaker in the anterior–posterior (0.78 ± 0.24) and medial–lateral directions (0.46 ± 0.44).ConclusionsThe proposed 4D‐MRI with slab‐selectively excited 3D radial sampling allows for improved blood SNR, vessel–tissue CR, and image quality.

Amplitude modulation rate dependent topographic organization of the auditory steady-state response in human auditory cortex

Periodic modulations of an acoustic feature, such as amplitude over a certain frequency range, leads to phase locking of neural responses to the envelope of the modulation. Using electrophysiological methods this neural activity pattern, also called the auditory steady-state response (aSSR), is visible following frequency transformation of the evoked response as a clear spectral peak at the modulation frequency. Despite several studies employing the aSSR that show, for example, strongest responses for ∼40 Hz and an overall right-hemispheric dominance, it has not been investigated so far to what extent within auditory cortex different modulation frequencies elicit aSSRs at a homogenous source or whether the localization of the aSSR is topographically organized in a systematic manner. The latter would be suggested by previous neuroimaging works in monkeys and humans showing a periodotopic organization within and across distinct auditory fields. However, the sluggishness of the signal from these neuroimaging works prohibit inferences with regards to the fine-temporal features of the neural response. In the present study, we employed amplitude-modulated (AM) sounds over a range between 4 and 85 Hz to elicit aSSRs while recording brain activity via magnetoencephalography (MEG). Using beamforming and a fine spatially resolved grid restricted to auditory cortical processing regions, our study revealed a topographic representation of the aSSR that depends on AM rate, in particular in the medial-lateral (bilateral) and posterior-anterior (right auditory cortex) direction. In summary, our findings confirm previous studies that showing different AM rates to elicit maximal response in distinct neural populations. They extend these findings however by also showing that these respective neural ensembles in auditory cortex actually phase lock their activity over a wide modulation frequency range.

Effect of sacroiliac manipulation on postural sway in quiet standing: a randomized controlled trial

BackgroundSacroiliac joint manipulation can alter joint and muscle control mechanisms through local and remote effects. Postural balance is controlled by supraspinal (rambling) and spinal–peripheral (trembling) mechanisms. A manipulation may interfere with postural control in quiet standing. ObjectivesTo evaluate the immediate effects of sacroiliac joint manipulation on postural control in patients with (1) sacroiliac dysfunction and (2) to determine whether rambling and trembling are affected by sacroiliac joint manipulation. Methods32 patients aged between 20 and 50 years old were selected by convenience after confirmation of sacroiliac joint dysfunction by clinical examination. These patients were randomly allocated either to manipulation or sham manipulation group. Displacement, velocity and frequency of the center of pressure, rambling and trembling in the anterior–posterior and medial–lateral directions were our primary outcomes and analyzed immediately before and after the intervention in quiet standing. The physical therapists who performed the physical, biomechanical and statistical examinations, were all blinded to the patients’ grouping. ResultsNo differences were found between the two groups but trembling velocity (0.14 and −0.11 for intervention and sham group, respectively) and frequency (0.17 and 0.11 for intervention and sham group respectively) increased after intervention in the treatment group in the anterior–posterior direction. ConclusionGenerally, sacroiliac joint manipulation had no superiority than sham treatment regarding postural control as measured by rambling–trembling analysis of center of pressure. Manipulation may increase muscle activation in the treatment group due to increased trembling parameters.Trial number: IRCT2014072715932N8 – http://www.irct.ir/searchresult.php?keyword=%D8%B3%D9%88%DB%8C%D9%87&id=15932&field=&number=8&prt=13&total=10&m=1.

Post-fatigue recovery of power, postural control and physical function in older women.

Low muscle power, particularly at high velocities, has been linked to poor physical function in older adults. Any loss in muscle power following fatiguing exercise or daily activities could impact physical function and postural control until power has fully recovered. To test the overall hypothesis that a common task such as walking can result in prolonged power loss and decreased physical function and balance, 17 healthy older (66–81 years) women completed a 32-min walking test (32MWT) designed to induce neuromuscular fatigue, followed by 60min of recovery (60R). Fatigue and recovery of knee extensor muscle power (3 velocities) were quantified by dynamometry. Function was quantified by chair rise time and postural control by measures of center of pressure (COP) range (mm) and velocity (mm·s-1) during quiet stance. Power declined at all velocities by 8–13% 2min following the 32MWT (p≤0.02) and remained depressed by 8–26% at 60R (p≤0.04). Postural control decreased following the 32MWT, indicated by increased COP range in the anterior-posterior (AP, p<0.01) direction and a trend in the medial-lateral (ML) direction (p = 0.09), and returned to baseline by 60R (p≥0.10). COP velocity was unchanged immediately following the 32MWT, but at 60R was lower in ML (p = 0.03) and tended to be reduced in AP (p = 0.07). Changes in high-velocity power (270°·s-1) were associated with altered postural control (p = 0.02) and chair rise performance (p≤0.03). These results provide evidence of long-duration neuromuscular changes following fatigue in healthy older women that may place them at increased risk for functional deficits during everyday mobility tasks.

Test-retest reliability of a balance testing protocol with external perturbations in young healthy adults

External perturbations are utilized to challenge balance and mimic realistic balance threats in patient populations. The reliability of such protocols has not been established. The purpose was to examine test-retest reliability of balance testing with external perturbations. Healthy adults (n=34; mean age 23 years) underwent balance testing over two visits. Participants completed ten balance conditions in which the following parameters were combined: perturbation or non-perturbation, single or double leg, and eyes open or closed. Three trials were collected for each condition. Data were collected on a force plate and external perturbations were applied by translating the plate. Force plate center of pressure (CoP) data were summarized using 13 different CoP measures. Test-retest reliability was examined using intraclass correlation coefficients (ICC) and Bland-Altman plots. CoP measures of total speed and excursion in both anterior-posterior and medial-lateral directions generally had acceptable ICC values for perturbation conditions (ICC=0.46 to 0.87); however, many other CoP measures (e.g. range, area of ellipse) had unacceptable test-retest reliability (ICC<0.70). Improved CoP measures were present on the second visit indicating a potential learning effect. Non-perturbation conditions generally produced more reliable CoP measures than perturbation conditions during double leg standing, but not single leg standing. Therefore, changes to balance testing protocols that include external perturbations should be made to improve test-retest reliability and diminish learning including more extensive participant training and increasing the number of trials. CoP measures that consider all data points (e.g. total speed) are more reliable than those that only consider a few data points.

Impaired Balancing Function in Patients of Chronic Mechanical Ankle Instability

Category: Ankle Introduction/Purpose: Chronic ankle instability (CAI) is a disease entity commonly seen after ankle ligament injury. It is divided into mechanical ankle instability (MAI) and functional ankle instability (FAI), with different pathological conditions. The purpose of this study was to test the balancing ability of MAI and FAI patients. Methods: 30 CAI patients and 10 normal subjects were included according to the injury history, clinical symptom and MRI presentation. Stress tests were given under fluoroscopy to find out those with mechanical instability in CAI patients. Among them there were 18 MAI and 12 FAI patients. All patients were tested on a customized balancing ability assessment system developed by Shanghai Jiaotong University. Subjects were asked to stand on the platform for 30 seconds for both feet, 10 seconds for single foot, with eyes open. And 30 seconds for both feet, 5 seconds for single foot, with eyes closed. Each condition was tested for 3 trials and results were averaged. Parameters of balance like the swaying trajectory length and speed at both medial-lateral and anterior-posterior directions, the trajectory length per unit were obtained. Results were compared among three groups. Results: The MAI group presented significantly greater imbalance in both medial-lateral and anterior-posterior directions compared with that in the control group while standing on the single diseased foot, with eyes open or closed. While in the FAI group, no significant difference was found in postural sway compared with that in the control group. The MAI group presented significantly greater imbalance in both medial-lateral and anterior-posterior directions than the FAI group while standing on the single diseased foot with eyes open or closed. No significant difference in balancing was found of the contralateral ankle in the two groups. Conclusion: The balancing ability of MAI patients was impaired and then make them vulnerable to falling. Thus either balance training program or reconstructive surgery is needed to restore the balancing ability in those patients.

Alterations of human responses by varying dynamic rotational perturbations on balance training equipment

Multiple studies investigated the correlation between balance and sports performance. Few studies, however, investigated control strategies for base plate rotational perturbation on balance training equipment to maximize balance-training efficiency. Thus, this study analyzed human responses by varying base plate rotational perturbations and provided fundamental data for strategy to maximize balance-training efficiency. Base plate rotation was controlled to induce dynamic rotational perturbations in the anteriorposterior (AP), right-diagonal (RD), medial-lateral (ML) and left-diagonal (LD) directions. A three-dimensional motion-capture, pedar flexible insoles and wireless surface electromyography systems were used. The joint angles, balance indices and muscle activations and co-contractions were significantly different in response to the dynamic rotational perturbations (p < 0.05). The joint angle and balance index changes were greater with AP and ML dynamic rotational perturbations than those in others (p < 0.05). In AP dynamic rotational perturbation, vastus lateralis and soleus activations were generally higher than those of other muscles (p < 0.05). Biceps femoris activation was particularly the highest in ML dynamic rotational perturbation. In conclusion, this study identified that specialized human responses occurred based on the base plate rotational perturbation characteristics on balancetraining equipment. These findings indicate that it may be necessary to control the base plate rotational perturbations corresponding to the sport characteristics.

Aging effect on step adjustments and stability control in visually perturbed gait initiation

Gait adaptability is essential for fall avoidance during locomotion. It requires the ability to rapidly inhibit original motor planning, select and execute alternative motor commands, while also maintaining the stability of locomotion. This study investigated the aging effect on gait adaptability and dynamic stability control during a visually perturbed gait initiation task. A novel approach was used such that the anticipatory postural adjustment (APA) during gait initiation were used to trigger the unpredictable relocation of a foot-size stepping target. Participants (10 young adults and 10 older adults) completed visually perturbed gait initiation in three adjustment timing conditions (early, intermediate, late; all extracted from the stereotypical APA pattern) and two adjustment direction conditions (medial, lateral). Stepping accuracy, foot rotation at landing, and Margin of Dynamic Stability (MDS) were analyzed and compared across test conditions and groups using a linear mixed model. Stepping accuracy decreased as a function of adjustment timing as well as stepping direction, with older subjects exhibited a significantly greater undershoot in foot placement to late lateral stepping. Late adjustment also elicited a reaching-like movement (i.e. foot rotation prior to landing in order to step on the target), regardless of stepping direction. MDS measures in the medial-lateral and anterior-posterior direction revealed both young and older adults exhibited reduced stability in the adjustment step and subsequent steps. However, young adults returned to stable gait faster than older adults. These findings could be useful for future study of screening deficits in gait adaptability and preventing falls.

Postural stability during long duration quiet standing in post stroke hemiplegia

Abstract Background Inter-limb center of pressure changes and stance asymmetry in individuals with hemiplegia secondary to stroke have previously been reported for short duration quiet standing (QS). The purpose of this investigation was to assess COP displacement, velocity, and loading forces during long duration (120 s) quiet standing. The investigation also aimed at performing an inter-limb stability assessment using COP distance and velocity dependent phase plane analysis during 120 s of quiet standing in healthy controls and individuals with hemiplegia post stroke. Methods Healthy adults (n = 12 control subjects) and individuals with hemiplegia secondary to stroke (n = 10) stood on a level floor with eyes open for 120 s while plantar pressure data was collected bilaterally. Main outcome variables included COP displacement, COP velocity, stability indices based on COP displacement and velocity variations, and the Berg Balance Assessment. In the stroke group, paired t-tests were used to perform inter-limb comparisons of the main COP outcome measures. Secondary analysis evaluated the inter-limb symmetry ratios for both groups, and independent sample t- tests were conducted to compare inter-limb ratios of COP, stability indices measures, and Berg Balance Assessment Scores between the two groups. Results In the stroke group, COP range, COP mean velocity, COP peak velocity, and stability indices were significantly asymmetrical and greater on non-paretic side in anterior-posterior (AP) direction. Individuals with stroke demonstrated symmetrical loading forces, COP range, RMS COP, COP velocity medial-lateral (ML) ratios and this was not significantly different from the healthy controls. Conclusion The majority of the weight bearing was imposed on the non-paretic side during 120 s of QS. As being the major contributor in maintaining balance, the non-paretic side may be over-utilized which may further lead to greater COP displacements, velocities, and potentially postural instability in AP direction. Such asymmetry in AP direction resulted in a compensatory weight “switching” strategy in ML direction.

The Effects of Footwear on Squat Movements

The purpose of this study was to compare the effects of different footwear (bare feet, flat-soled shoes, and weightlifting shoes) on balance during a barbell back squat in novice and advanced participants. It was hypothesized that i) weightlifting shoes would increase balance performance in the anterior-posterior (AP) and medial-lateral (ML) directions, and ii) advanced participants would demonstrate increased balance performance in the AP and ML direction compared to novice participants. 17 participants (9 novice and 8 advanced) performed 3 trials of a single squat repetition, using a 45lb Olympic standard barbell on a force plate, with bare feet, flat shoes, and weightlifting shoes. Squat 1 and 2 were used as warm-up repetitions and data was collected during squat 3 of each condition. Participants were characterized as either novice or advanced based on the number of training sessions they performed squats each week. Novice participants squatted with a barbell less than once per week, and advanced squatted with a barbell more than once per week. Balance performance was quantified by the percentage of time the centre of pressure (CoP) had the smallest displacement from the average CoP location. A chi-square test was performed to determine the statistically significant changes in CoP displacement between the 3 footwear conditions; accordingly, the post hoc significance interval was calculated to P0.0167). Using a 2-way ANOVA, no significant differences were found between novice and advanced participants’ root mean square values for normalized CoP in the AP or ML directions (P&gt;0.05). Participants during the weightlifting shoe condition were found to have better regulation of balance compared to bare feet or flat shoes conditions. Additionally, it was found that novice and advanced participants did not regulate balance differently from each other during the squat movement.

The Effect of Plantar Flexor Fatigue and Cognitive Recall Task on Standing Balance

Introduction: Previous studies have shown that fatigue of the plantar flexor muscles and mental tasks each can lead to impaired balance. The purpose of this study is to analyze the effects of a combined increase in cognitive load and plantar flexor fatigue can have on standing balance.&#x0D; Methods: Fifteen (7 males, 8 females) healthy individuals participated in one testing session. Prior to testing, participants were screened for existing balance and plantar flexor health issues via a medical history questionnaire. Participants performed a total of twelve standing balance trials, each 30 seconds in duration. These trials consisted of three control, three recall, three fatigue, and three fatigue recall trials. For each trial, participants closed their eyes and stood with their feet together on a force plate. Recall ability was evaluated based on the participant’s ability to accurately complete the reverse digit recall section of the SCAT-3. Plantar flexor fatigue was achieved by performing five repetitions of standing calf raises. Each repetition consisted of a five second eccentric contraction, a five second concentric contraction, and a five second isometric contraction. The means of the 90% radius of the center of pressure was compared to the standing baseline across all conditions.&#x0D; Results:Similar significant differences were found across 90% radius and center of pressure in both medial-lateral and anterior-posterior directions. Across all three variables, the recall condition was not significantly different (p&gt;0.05) than control standing. Both fatigue and fatigue recall conditions were significantly different (p&lt;0.05)&#x0D; Conclusion: Collectively, the data indicates that fatigue, rather than recall, had a greater effect on all measured variables of balance. This suggests that balance is a primarily muscle driven task, and not a mental task.

Three-dimensional evaluation ofposturalstability in Parkinson's disease with mobile technology.

Postural instability is a hallmark of Parkinson's disease. Objective metrics to characterize postural stability are necessary for the development of treatment algorithms to aid in the clinical setting. The aim of this project was to validate a mobile device platform and resultant three-dimensional balance metric that characterizes postural stability. A mobile Application was developed, in which biomechanical data from inertial sensors within a mobile device were processed to characterize movement of center of mass in the medial-lateral, anterior-posterior and trunk rotation directions. Twenty-seven individuals with Parkinson's disease and 27 age-matched controls completed various balance tasks. A postural stability metric quantifying the amplitude (peak-to-peak) of sway acceleration in each movement direction was compared between groups. The peak-to-peak value in each direction for each individual with Parkinson's disease across all trials was expressed as a normalized value of the control data to identify individuals with severe postural instability, termed Cleveland Clinic-Postural Stability Index. In all conditions, the balance metric for peak-to-peak was significantly greater in Parkinson's disease compared to controls (p < 0.01 for all tests). The balance metric, in conjunction with mobile device sensors, provides a rapid and systematic metric for quantifying postural stability in Parkinson's disease.

O63: Medial gastrocnemius muscle in children with Spastic Paresis show growth defects for muscle volume and altered normalized muscle and tendon length compared to typically developed children

Gait adaptability is essential for fall avoidance during locomotion. It requires the ability to rapidly inhibit original motor planning, select and execute alternative motor commands, while also maintaining the stability of locomotion. This study investigated the aging effect on gait adaptability and dynamic stability control during a visually perturbed gait initiation task. A novel approach was used such that the anticipatory postural adjustment (APA) during gait initiation were used to trigger the unpredictable relocation of a foot-size stepping target. Participants (10 young adults and 10 older adults) completed visually perturbed gait initiation in three adjustment timing conditions (early, intermediate, late; all extracted from the stereotypical APA pattern) and two adjustment direction conditions (medial, lateral). Stepping accuracy, foot rotation at landing, and Margin of Dynamic Stability (MDS) were analyzed and compared across test conditions and groups using a linear mixed model. Stepping accuracy decreased as a function of adjustment timing as well as stepping direction, with older subjects exhibited a significantly greater undershoot in foot placement to late lateral stepping. Late adjustment also elicited a reaching-like movement (i.e. foot rotation prior to landing in order to step on the target), regardless of stepping direction. MDS measures in the medial-lateral and anterior-posterior direction revealed both young and older adults exhibited reduced stability in the adjustment step and subsequent steps. However, young adults returned to stable gait faster than older adults. These findings could be useful for future study of screening deficits in gait adaptability and preventing falls.

Dynamic balance changes within three weeks of fitting a new prosthetic foot component

Balance during walking is of high importance to prosthesis users and may affect walking during baseline observation and evaluation. The aim of this study was to determine whether changes in walking balance occurred during an adaptation period following the fitting of a new prosthetic component.Margin of stability in the medial-lateral direction (MOSML) and an anterior instability margin (AIM) were used to quantify the dynamic balance of 21 unilateral transtibial amputees during overground walking. Participants trialled two prosthetic feet presenting contrasting movement/balance constraints; a Higher Activity foot similar to that of their own prosthesis, and a Lower Activity foot. Participants were assessed before (Visit 1) and after (Visit 2) a 3-week adaptation period on each foot.With the Higher Activity component, MOSML decreased on the prosthetic side, and increased on the sound side from Visit 1 to Visit 2, eliminating a significant inter-limb difference apparent at Visit 1 (Visit 1–sound=0.062m, prosthetic=0.075m, p=0.018; Visit 2–sound=0.066m, prosthetic=0.074m, p=0.084). No such change was seen with the Lower Activity foot (Visit 1–sound=0.064m, prosthetic=0.077m, p=0.007; Visit 2–sound=0.063m, prosthetic=0.080m, p<0.001). Significant changes in AIM were observed at Visit 2 (Visit 1: −0.16 (0.08) m, Visit 2: −0.17 (0.08) m; F=23.396, p<0.01).These findings suggest that changes in balance during walking can occur following the initial receipt of a device regardless of whether the component is of the same functional category as the one an individual is accustomed to using.

How does cryotherapy effect ankle proprioception in healthy individuals?

Objectives To investigate how a 15-min cryotherapy intervention effects proprioception by measuring joint positional sense (JPS) and static single legged balance. Design Repeated measures design. Setting Laboratory. Participants Eighteen healthy university sports team students (11 males, 7 females) aged between 20 and 21 years old. Main outcome measures Participants were treated with 15 min of Aircast Cryo-cuff. The subject’s skin temperature was measured before and immediately after 15 min of cryotherapy treatment. Ankle active joint positional sense (A-JPS) and passive joint positional sense (P-JPS) were measured at pre-test, immediately post-test, and 5 min post-test. Static balance was measured by centre of pressure (CoP) mean path length, medial–lateral (ML) CoP mean deviation, and anterior–posterior (AP) CoP mean deviation and mean time-to-boundary (TtB) minima for AP and ML directions. Results No significant differences were found for the variables of JPS and static single balance testing after 15 min of cryotherapy treatment. However, mean differences for CoP mean path length and ML mean deviation were shown to improve following cryotherapy treatment, results not previously found in the literature. Conclusion Results suggest that 15 min of Cryo-cuff treatment does not significantly affect proprioception. Although the effect of cryotherapy on proprioception depends on cooling modality used, time frame applied, and joint applied to.

Evaluation of postural instability in stroke patient during quiet standing.

This study was designed to investigate the postural instability in stroke survivals during quiet standing. Eleven stroke patients and 11 healthy volunteers (gender- and age-matched) were recruited for this experiment. The center of pressure (COP) signals from both planta in anterior-posterior (AP) and medial-lateral (ML) directions were recorded using a three-dimensional motion capture system (BTS Bioengineering Corp, Italy) when subjects stood on the two adjacent force platforms quietly with their eyes open (EO) for 30 s and with their eyes close (EC) for another 30 s. The standard deviation (SD) for the two limbs and the inter-limb cross correlation-coefficient (CC) of COP series were calculated under EO and EC conditions, respectively. Patients showed significant differences in SD of AP-COP between two sides under EO (p <; 0.05) and EC (p <; 0.001) conditions. The SD of the ML-COP on non-paretic limb of patients was higher than that of controls under EC (p <; 0.05). Lower CC values of AP-COP was found in patients versus controls under two vision conditions (p <; 0.05), and the values in two groups increased significantly after removal of vision information (p <; 0.05). Stroke led to an increased postural sway and decreased inter-limb coordination during quiet standing. This study may facilitate the evaluation of the standing instability in stroke survivors and may improve the strategies for rehabilitation.

The Effect of Complex Ankle Exercises on Balance with Functional Ankle Instability in Twenties

The purpose of this study was to investigate the complex ankle exercises on balance. 22 participants (male: 14, female: 8) with functional ankle instability were participated. Functional ankle instability was selected to be less than 24 points using the Cumberland ankle instability tool (CAIT) with people who had severe ankle sprain and then experiencing ankle giving way. A total of 20 minutes performed three times a week for four weeks with muscle strength and balance exercises. Muscle strengthening exercise was performed with Theraband, and balance exercise was performed with unstable support plates. Biodex balance systemⓇ was used to measure static and dynamic balance. The dynamic balance was selected in grade 2, 4, and 8. The static and dynamic balance (grade: 2, 4,and 8) balance was significantly decreased in anterior-posterior, and medial-lateral directions (p<.05). The instability was significantly increased after exercise (p<.05). These results suggest that complex exercises are beneficial to decreasing the functional ankle instability.

Standing on wedges modifies side-specific postural control in the presence of lateral external perturbations

Standing on wedges changes the position in the ankle joints and affects postural stability in the medial-lateral direction. The objective of the study was to investigate the role of wedges and external lateral perturbations on anticipatory (APA) and compensatory postural adjustments (CPA). Ten healthy young participants were exposed to perturbations applied to the lateral part of their right shoulder when standing on a planar surface, on a medial or lateral wedges. Bilateral electromyographic activity of dorsal and ventral postural muscles and the center of pressure (COP) displacement were recorded and analyzed during the APA and CPA phases. When exposed to the lateral perturbation, reciprocal activation of shank muscles was seen on the side of the perturbation while co-contraction of shank muscles was seen on the contralateral side during the APA and CPA phases. Standing on a wedge was associated with decreased magnitudes of co-contraction and reciprocal activation of shank muscles. The COP displacements were smaller in the APA phase and larger in the CPA phase while standing on wedges compared to standing on the planar surface. The outcome of the study provides a basis for future investigations of incorporating wedges in balance re-training paradigms for the elderly or individuals with neurological impairment.

Investigating Human Balance and Postural Control During Bilateral Stance on BOSU Balance Trainer

Balance and postural control are essential for performing activities of daily living to minimize risks of fall and injury. A proven way to improve postural stability and the perception of the somatosensory system is to utilize devices such as the BOSU balance trainer, wobble board and seesaw platform. It was reported that performing unilateral stance on BOSU could stimulate and eventually improve human neuromuscular system in maintaining body balance. However, this posture is challenging and may not be suitable for individuals with sedentary lifestyle. Therefore, this study investigates the ability of human postural control while performing bilateral stance on BOSU. Increase in center of pressure measures e.g. sway area, sway velocity, and the range of excursion in both anterior–posterior and medial–lateral directions were observed when subjects stood on BOSU, as compared to when they stood on the flat ground (p < 0.01). This study also found that vision played an important role in challenging environment. Significant differences were found when subjects were standing on BOSU with eyes closed and eyes open (p < 0.01). Hence, it can be deduced that bilateral stance on BOSU can stimulate neuromuscular system to coordinate the lower extremity in order to mitigate the instability and to reduce the risk of fall. Individuals with sedentary lifestyle or impaired balance, or patients who are recovering from minor ankle or knee injury can perform bilateral stance on BOSU, instead of unilateral stance to improve their balance and postural control.

Effects of hip joint centre mislocation on gait kinematics of children with cerebral palsy calculated using patient-specific direct and inverse kinematic models

Joint kinematics can be calculated by Direct Kinematics (DK), which is used in most clinical gait laboratories, or Inverse Kinematics (IK), which is mainly used for musculoskeletal research. In both approaches, joint centre locations are required to compute joint angles. The hip joint centre (HJC) in DK models can be estimated using predictive or functional methods, while in IK models can be obtained by scaling generic models. The aim of the current study was to systematically investigate the impact of HJC location errors on lower limb joint kinematics of a clinical population using DK and IK approaches. Subject-specific kinematic models of eight children with cerebral palsy were built from magnetic resonance images and used as reference models. HJC was then perturbed in 6mm steps within a 60mm cubic grid, and kinematic waveforms were calculated for the reference and perturbed models. HJC perturbations affected only hip and knee joint kinematics in a DK framework, but all joint angles were affected when using IK. In the DK model, joint constraints increased the sensitivity of joint range-of-motion to HJC location errors. Mean joint angle offsets larger than 5° were observed for both approaches (DK and IK), which were larger than previously reported for healthy adults. In the absence of medical images to identify the HJC, predictive or functional methods with small errors in anterior-posterior and medial-lateral directions and scaling procedures minimizing HJC location errors in the anterior-posterior direction should be chosen to minimize the impact on joint kinematics.