Changes In Center Of Pressure Research Articles

Effects of Cognitive Inhibition Preceding Voluntary Step Responses to Visual Stimuli in Young and Older Adults.

Age-related changes in executive functions, especially inhibitory control, correlate to decreased balance control and increased fall risk. However, only a few studies focused on the performance of tasks integrating balance and inhibitory control. This study aims to determine the effects of cognitive inhibition preceding the initiation of voluntary steps in young and older adults. Performance of 3 stepping tasks (a Simon, Flanker, and a combined Simon-Flanker task [SFT]) were analyzed in 23 young adults and 43 older adults. Each task included congruent and incongruent trials in different step directions. Analyses focused on temporal aspects of step responses as identified by changes in Center of Pressure (CoP) and foot position. A 3-way repeated-measures ANOVA was used to evaluate "inhibition," "age," and "task" effects. With large effect sizes, "inhibition" as well as "age" resulted in longer durations of an initial preparatory phase as well as the step response phase. The SFT showed the largest "task" effects. Duration of CoP movement had the largest impact on total step execution in older adults. A significant interaction effect of "age*inhibition" was found on the duration of CoP movement, but not on CoP onset. Overall, our results demonstrate that cognitive inhibition has more impact in older adults, the longer duration of CoP movements in older adults may reflect an ineffective step preparation. Our examination of the duration of subsequent phases which comprise perceptual processing and conflict resolution, response initiation, and step execution sheds light on how cognitive inhibition affects voluntary stepping behavior in young and older adults.

Effects of arousal and valence on center of pressure and ankle muscle activity during quiet standing.

Emotion affects postural control during quiet standing. Emotional states can be defined as two-dimensional models comprising valence (pleasant/unpleasant) and arousal (aroused/calm). Most previous studies have investigated the effects of valence on postural control without considering arousal. In addition, studies have focused on the center of pressure (COP) trajectory to examine emotional effects on the quiet standing control; however, the relationship between neuromuscular mechanisms and the emotionally affected quiet standing control is largely unknown. This study aimed to investigate the effects of arousal and valence on the COP trajectory and ankle muscle activity during quiet standing. Twenty-two participants were instructed to stand on a force platform and look at affective pictures for 72 seconds. The tasks were repeated six times, according to the picture conditions composed of arousal (High and Low) and valence (Pleasant, Neutral, and Unpleasant). During the task, the COP, electromyogram (EMG) of the tibialis anterior and soleus muscles, and electrocardiogram (ECG) were recorded. The heart rate calculated from the ECG was significantly affected by valence; the value was lower in Unpleasant than that in Neutral and Pleasant. The 95% confidence ellipse area and standard deviation of COP in the anterior-posterior direction were lower, and the mean power frequency of COP in the anterior-posterior direction was higher in Unpleasant than in Pleasant. Although the mean velocity of the COP in the medio-lateral direction was significantly lower in Unpleasant than in Pleasant, the effect was observed only when arousal was low. Although the EMG variables were not significantly affected by emotional conditions, some EMG variables were significantly correlated with the COP variables that were affected by emotional conditions. Therefore, ankle muscle activity may be partially associated with postural changes triggered by emotional intervention. In conclusion, both valence and arousal affect the COP variables, and ankle muscle activity may be partially associated with these COP changes.

The Effect of Biomechanics Information on Driver Swing Learning of Intermediate Golfers

PURPOSE This study investigates the effectiveness of biomechanics information on intermediate golfers driver swing learning. It analyzes changes in center of pressure (COP) patterns, GRF Direction Inclination, driver performance, and learners psychological responses to determine the learning effects.METHODS Subjects were 32 right-handed male golfers (handicap 15-23) who had no difficulty in performing the golf driver swing (Full swing). Four groups were selected, BF (Biomechanics Feedback group), BVC (Biomechanics Verbal Cue group), CB (Combination group), and CT (Control group), and assigned randomly. Driver swing learning showed results after 6 weeks,and a transfer test was conducted 1 week after the completion of the learning.RESULTS Analysis of COP patterns and GRF Direction Inclination indicated changes in the BF, BVC, and CB groups. Furthermore, analysis of driver distance (m), club head speed (km/h), and ball spin rate (rpm) revealed that during the 6-week acquisition phase, all three groups (excluding the control group) showed improvements in driver distance, club head speed, and ball spin rate. However, there were no statistically significant differences among the groups. In contrast, the transfer test showed statistically significant differences among the groups, with the CB group exhibiting the highest driver distance. Learners' psychological responses during the learning process were trust, understanding, and satisfaction. The understanding factor was relatively higher in the CB and BVC groups compared to the BF group.CONCLUSIONS In summary, biomechanics information (BI) was effective in improving driver performance, and changesappeared in the COP pattern and GRF Direction Inclination, indicating a change in movement. Therefore, BI can be fully utilized for athletes or high-level advanced players and for motor learning for intermediate-level students.However, BI can only improve learning effects by strengthening learners' “understanding” when visual feedback forms and verbal cues are provided together.

Postural adjustment in standing position when catching a ball under unpredictable conditions of the direction to be caught

BackgroundBalanced postural control of the body is associated with two mechanisms: anticipatory postural adjustment and compensatory postural adjustment. Previous studies reported changes in body postural control under unpredictable conditions (interference with closed eyes). Research questionTo ascertain whether in contrast with predictable disturbances, there is a difference in muscle activity and center of pressure displacement changes when the direction of the disturbance is unpredictable. MethodsThree examiners stood at 45° to the left, the front, and 45° to the right of the participant to throw the ball to him. 11 healthy young participants were required to maintain their balance in the standing position after receiving the ball in conditions with and without known catching directions. The anticipatory postural adjustment and compensatory postural adjustment integral changes of the muscle activity in the lower limbs and trunk bilaterally and at the center of pressure displacement in the known and unknown conditions were observed. Two-way ANOVA was used to compare the differences in muscle activity and displacement changes. ResultsResults showed that the center of pressure in the anticipatory postural adjustment and compensatory postural adjustment in the posterior direction with known catching direction was significantly shorter than those without. Integration of electromyogram in anticipatory postural adjustment of the right soleus (p = 0.023) was associated with higher muscle activities in the unknown than known conditions. Integration of electromyogram in compensatory postural adjustment of the right tibial anterior (p = 0.004), right rectus femoris (p = 0.023) and left rectus abdominis (p = 0.038) in unknown catching direction had significantly greater muscle activity than those without. When the direction of the perturbation is unpredictable, the central nervous system may initiate and induce greater center of pressure changes in the posterior direction with changes in several muscular activities to ensure postural control.

Development of an Evaluation System for Transfer Care Skills Using Embroidered Body Pressure and Proximity Sensor.

It is important to improve caregiving skills to help reduce the strain on inexperienced caregivers. Previous studies on quantifying caregiving skills have predominantly relied on expensive equipment, such as motion-capture systems with multiple infrared cameras or acceleration sensors. To overcome the cost and space limitations of existing systems, we developed a simple evaluation system for transfer care skills that uses capacitive sensors composed of conductive embroidery fibers. The proposed system can be developed with a few thousand US dollars. The developed evaluation system was used to compare the seating position and velocity of a care recipient during transfers from a nursing-care bed to a wheelchair between groups of inexperienced and expert caregivers. To validate the proposed system, we compare the motion data measured by our system and the data obtained from a conventional three-dimensional motion-capture system and force plate. We analyze the relationship between changes in the center of pressure (CoP) recorded by the force plate and the center of gravity (CoG) obtained by the developed system. Evidently, the changes in CoP have a relation with the CoG. We show that the actual seating speed ([Formula: see text] measured by the motion-capture system is related to the speed coefficient calculated from our sensor output. A significant difference exists in [Formula: see text] between the inexperienced group and the physical therapists/occupational therapists' group. The proposed system can effectively estimate a caregiver's skill level in transferring patients from a bed to a wheelchair in terms of the seating position and velocity.

Predicting postural control adaptation measuring EEG, EMG, and center of pressure changes: BioVRSea paradigm.

Introduction: Postural control is a sensorimotor mechanism that can reveal neurophysiological disorder. The present work studies the quantitative response to a complex postural control task. Methods: We measure electroencephalography (EEG), electromyography (EMG), and center of pressure (CoP) signals during a virtual reality (VR) experience called BioVRSea with the aim of classifying different postural control responses. The BioVRSea paradigm is based on six different phases where motion and visual stimulation are modulated throughout the experiment, inducing subjects to a different adaptive postural control strategy. The goal of the study is to assess the predictability of those responses. During the experiment, brain activity was recorded from a 64-channel EEG, muscle activity was determined with six wireless EMG sensors placed on lower leg muscles, and individual movement measured by the CoP. One-hundred and seventy-two healthy individuals underwent the BioVRSea paradigm and 318 features were extracted from each phase of the experiment. Machine learning techniques were employed to: (1) classify the phases of the experiment; (2) assess the most notable features; and (3) identify a quantitative pattern for healthy responses. Results: The results show that the EEG features are not sufficient to predict the distinct phases of the experiment, but they can distinguish visual and motion onset stimulation. EMG features and CoP features, when used jointly, can predict five out of six phases with a mean accuracy of 74.4% (±8%) and an AUC of 0.92. The most important feature to identify the different adaptive strategies is the Squared Root Mean Distance of points on Medio-Lateral axis (RDIST_ML). Discussion: This work shows the importance and the feasibility of a quantitative evaluation in a complex postural control task and demonstrates the potential of EEG, CoP, and EMG for assessing pathological conditions. These predictive systems pave the way for developing an objective assessment of pathological behavior PC responses. This will be a first step in identifying individual disorders and treatment options.

Design of pediatric robot to simulate infant biomechanics for neuro-developmental assessment in a sensorized gym.

Infants at risk for developmental delays often exhibit postures and movements that may provide a window into potential impairment for cerebral palsy and other neuromotor conditions. We developed a simple 4 DOF robot pediatric simulator to help provide insight into how infant kinematic movements may affect the center of pressure (COP), a common measure thought to be sensitive to neuromotor delay when assessed from supine infants at play. We conducted two experiments: 1) we compared changes in COP caused by limb movements to a human infant and 2) we determined if we could predict COP position due to limb movements using simulator kinematic pose retrieved from video and a sensorized mat. Our results indicate that the limb movements alone were not sufficient to mimic the COP in a human infant. In addition, we show that given a robot simulator and a simple camera, we can predict COP measured by a force sensing mat. Future directions suggest a more complex robot is needed such as one that may include trunk DOF.

102. An introductory investigation of standing postural control ‘error’ and its relation to balance in adult spinal deformity surgery patients

102. An introductory investigation of standing postural control ‘error’ and its relation to balance in adult spinal deformity surgery patients

The Application of Balance Exercise Using Virtual Reality for Rehabilitation.

To prevent falls, it is important to devise a safe balance training program that can be easily performed. This study investigated whether tilting an image in virtual reality (VR) can generate a center-of-gravity sway. Five men and five women were asked to rest standing upright (control condition) and to rest standing upright with a head-mounted display showing a tilted virtual image (VR condition), and changes in their standing balance were observed. Standing balance was assessed by measuring the distance traveled by the center of pressure (COP) of each of the participants’ legs. In order to investigate the effects of different tilt speeds and angles on COP, four different images were displayed in VR: an image tilting to 10° moving at a rate of 1°/s; an image tilting to 20° moving 1°/s; an image tilting to 10° moving 10°/s; an image tilting to 20° moving 10°/s. Change in COP was significantly greater in the VR than in the control condition (p < 0.01), and a tilt of 10° moving 1°/s showed the greatest change in COP (p < 0.01). Tilting an image in VR while in a resting standing position can change an individual’s COP; thus, VR may be applied to balance training.

Quantifying fear of falling by utilizing objective body sway measures: A 360° virtual video study

BackgroundFear of falling (FOF) is a psychological condition that can lead to increased morbidity and mortality in the elderly population. However, the subjective and multidimensional nature of FOF results in limitations of existing FOF measurement tools, which could influence the generalization of the findings from various studies. An objective measure of FOF could address those limitations. The present study aimed to identify the feasibility of using center of pressure (COP) parameters to quantify FOF. Research question(1) Are 360º roller coaster videos effective to induce FOF? And (2) Which COP parameter(s) is/are feasible to quantify FOF? MethodsNineteen young, healthy adults (24 ± 2.47 years) were recruited in the present study. Subjects were required to watch three 360º videos: one control video and two roller coaster videos, through virtual reality goggles during standing and sitting. Six trials (3 during standing and 3 during sitting) with video were performed. Subjects were required to rate their FOF on a visual analogue scale after watching each video. COP mean power frequency, COP root mean square, and COP range were measured. The Friedman test was used to assess differences in COP parameters under different video conditions, and Spearman’s correlation analysis was used to assess the relationship between FOF and COP parameters. ResultsSimilar COP changes were observed in sitting and standing conditions. With increased FOF, participants demonstrated decreased COP mean power frequency and increased COP root mean square in the medial-lateral direction during both sitting and standing. SignificanceOur study provided evidence that 360º roller coaster videos are effective tools to induce FOF and change in COP parameters. The relationship between FOF and COP parameters suggests that the measurement of body sway may be an objective way to quantify FOF. More research are needed to solidify the evidence.

Changes in Center of Pressure after Robotic Exoskeleton Gait Training in Adults with Acquired Brain Injury.

Acquired brain injury (ABI) resulting in hemiplegia, is one of the leading causes of gait and balance deficits in adults. Gait and balance deficits include reduced momentum for forward progression, reduced step length, increased spatial and temporal asymmetry, and decreased speed; resulting in reduced functional ambulation, activities of daily living, and quality of life. Wearable lower extremity robotic exoskeletons (REs) are becoming an effective method for gait neurorehabilitation in individuals with ABI. REs can provide high dose, consistent, goal-directed repetition of movements as well as balance & stability for individuals with ABI. The objective of this study is to understand the effect of RE gait training using center of pressure (COP) displacement, temporal & spatial parameters, and functional outcomes for individuals with ABI. The results from this investigation show improved anterior-posterior COP displacement & rate of progression, spatial symmetry, step length, walking speed, and decreased time during the gait cycle. These preliminary results suggest that high dose, repetitive gait training using robotic exoskeletons has the potential to induce recovery of function in adults diagnosed with ABI.

Comparison of the Ground Reaction Force, Center of Mass to Center of Pressure Changes, and Time to Stabilization During a Jump in Young Professional and Semiprofessional Karate Girls

Background and Aims: Since there is a direct relationship between achieving the best athletic performance and minimizing the damage and the potential injuries with people’s ability to perform the technique, this study aimed at comparing the selected biomechanical variables during consecutive jump-landings between professional and semi-professional karate athletes. Methods: In the current study, using a force plate, the ground reaction force, changes of the center of mass to the center of pressure, and stabilization time during jump-landing of nine young members of the female karate national team (professional) and nine selected karate athletes of Mazandaran province (semi-professional), on their both right and left legs separately, were obtained and statistically analyzed. Results: In the information collected from the selected biomechanical variables, the average and standard deviation in the left foot of both groups were higher than in the right foot. There was a significant difference between the ground reaction force and the change of center of mass to the center of pressure (stress) in the internal-external non – professional karate athletes and the left foot of the professional and non-professional. There was a significant difference between the ground reactions force in the posterior-anterior direction between the right and left foot of the professional group and the right and left foot of the non – professional group and the right and left foot of both groups in the change of center of mass to the center of pressure between the right and left foot of these two groups. However, there was no significant difference in the stabilization time. Conclusion: According to the results, the variables of the ground reaction force and changes in the center of mass to the center of pressure, and the time needed to achieve stability for karate athletes can be used as an index to evaluate the level of ability to perform and detect the potential injuries occurrence in professional and semi-professional karate athletes.

Corticospinal Excitability of the Lower Limb Muscles During the Anticipatory Postural Adjustments: A TMS Study During Dart Throwing.

Objective: To investigate whether the changes in the corticospinal excitability contribute to the anticipatory postural adjustments (APAs) in the lower limb muscles when performing the ballistic upper limb movement of the dart throwing.Methods: We examined the primary motor cortex (M1) excitability of the lower limb muscles [tibialis anterior (TA) and soleus (SOL) muscles] during the APA phase by using transcranial magnetic stimulation (TMS) in the healthy volunteers. The surface electromyography (EMG) of anterior deltoid, triceps brachii, biceps brachii, TA, and SOL muscles was recorded and the motor evoked potential (MEP) to TMS was recorded in the TA muscle along with the SOL muscle. TMS at the hotspot of the TA muscle was applied at the timings immediately prior to the TA onset. The kinematic parameters including the three-dimensional motion analysis and center of pressure (COP) during the dart throwing were also assessed.Results: The changes in COP and EMG of the TA muscle occurred preceding the dart throwing, which involved a slight elbow flexion followed by an extension. The correlation analysis revealed that the onset of the TA muscle was related to the COP change and the elbow joint flexion. The MEP amplitude in the TA muscle, but not that in the SOL muscle, significantly increased immediately prior to the EMG burst (100, 50, and 0 ms prior to the TA onset).Conclusion: Our findings demonstrate that the corticospinal excitability of the TA muscle increases prior to the ballistic upper limb movement of the dart throwing, suggesting that the corticospinal pathway contributes to the APA in the lower limb in a muscle-specific manner.

People with persistent postural-perceptual dizziness demonstrate altered postural strategies in complex visual and cognitive environments.

People with PPPD report imbalance, increase in symptoms and impaired function within complex visual environments, but understanding of the mechanism for these behaviors is still lacking. To investigate postural control in PPPD we compared changes in center of pressure (COP) and head kinematics of people with PPPD (N = 22) and healthy controls (N = 20) in response to different combinations of visual and cognitive perturbations during a challenging balance task. Participants stood in a tandem position. Static or moving stars (0.2 Hz, 5 mm or 32 mm amplitude, anterior-posterior direction) were displayed through a head-mounted display (HTC Vive). On half the trials, participants performed a serial-3 subtraction task. We measured medio-lateral and anterior-posterior path and acceleration of COP and head. Controls significantly increased all COP and head parameters with the cognitive task whereas PPPD increased only COP ML path and acceleration. Only controls significantly increased head anterior-posterior & medio-lateral acceleration with moving visual load. Cognitive task performance was similar between groups. We observed altered postural strategies in people with PPPD, in the form of reduced movement with challenge, particularly around the head segment. The potential of this simple and portable head-mounted display setup for differential diagnosis of vestibular disorders should be further explored.

Low Back Pain Exacerbation Is Predictable Through Motif Identification in Center of Pressure Time Series Recorded During Dynamic Sitting.

Background: Low back pain (LBP) is a common health problem — sitting on a chair for a prolonged time is considered a significant risk factor. Furthermore, the level of LBP may vary at different times of the day. However, the role of the time-sequence property of sitting behavior in relation to LBP has not been considered. During the dynamic sitting, small changes, such as slight or big sways, have been identified. Therefore, it is possible to identify the motif consisting of such changes, which may be associated with the incidence, exacerbation, or improvement of LBP.Method: Office chairs installed with pressure sensors were provided to a total of 22 office workers (age = 43.4 ± 8.3 years) in Japan. Pressure sensors data were collected during working days and hours (from morning to evening). The participants were asked to answer subjective levels of pain including LBP. Center of pressure (COP) was calculated from the load level, the changes in COP were analyzed by applying the Toeplitz inverse covariance-based clustering (TICC) analysis, COP changes were categorized into several states. Based on the states, common motifs were identified as a recurring sitting behavior pattern combination of different states by motif-aware state assignment (MASA). Finally, the identified motif was tested as a feature to infer the changing levels of LBP within a day. Changes in the levels of LBP from morning to evening were categorized as exacerbated, did not change, or improved based on the survey questions. Here, we present a novel approach based on social spider algorithm (SSA) and probabilistic neural network (PNN) for the prediction of LBP. The specificity and sensitivity of the LBP inference were compared among ten different models, including SSA-PNN.Result: There exists a common motif, consisting of stable sitting and slight sway. When LBP level improved toward the evening, the frequency of motif appearance was higher than when LBP was exacerbated (p < 0.05) or the level did not change. The performance of the SSA-PNN optimization was better than that of the other algorithms. Accuracy, precision, recall, and F1-score were 59.20, 72.46, 40.94, and 63.24%, respectively.Conclusion: A lower frequency of a common motif of the COP dynamic changes characterized by stable sitting and slight sway was found to be associated with the exacerbation of LBP in the evening. LBP exacerbation is predictable by AI-based analysis of COP changes during the sitting behavior of the office workers.

Classification of wheelchair pressure relief maneuvers using changes in center of pressure and weight on the seat

Background Pressure injuries from prolonged sitting are a significant problem for wheelchair users incurring high costs in healthcare expenditures and reducing quality-of-life. There is a need to improve pressure relief training and adherence in a variety of settings. Objective To identify effective common wheelchair pressure relief (PR) manoeuvres based on changes to users’ seated centre of pressure (CoP) and seated weight. Participants 20 individuals who use manual wheelchairs as their primary means of mobility Methods Participants performed 5 types of PR including seated push-ups, leftward, rightward, forward, and backward leans—while sitting in a wheelchair equipped with a custom instrumented seat pan support. Data were analysed using both clustering and decision tree approaches to identify types of PR. Results Both clustering and decision tree approaches were able to identify and classify PR though neither could accurately distinguish between forward and backward PR. Conclusion Changes in the centre of pressure and the total weight on the wheelchair’s seat can be used to automatically characterise type, amplitude and duration of pressure relief manoeuvres. Building such a classification and quality assessment scheme into an algorithm could enable a virtual coaching system to track users’ pressure relief behaviour and make suggestions to improve adherence with clinical recommendations. IMPLICATIONS FOR REHABILITATION Multiple bending beam load cells can be used to measure wheelchair users’ seated centre of pressure independent of type of cushion used. Both cluster analysis and decision tree algorithms can classify commonly practiced pressure reliefs by measuring changes to the centre of pressure and total weight on the wheelchair’s seat. The combination of force sensing for centre of pressure determination and either algorithm could serve as the basis for an application to coach wheelchair users to do effective pressure reliefs.

Effects of additional load at different heights on gait initiation: A statistical parametric mapping of center of pressure and center of mass behavior.

The purpose of this study was to investigate the effects of different vertical positions of an asymmetrical load on the anticipatory postural adjustments phase of gait initiation. Sixty-eight college students (32 males, 36 females; age: 23.65 ± 3.21 years old; weight: 69.98 ± 8.15 kg; height: 1.74 ± 0.08 m) were enrolled in the study. Ground reaction forces and moments were collected using two force platforms. The participants completed three trials under each of the following random conditions: no-load (NL), waist uniformly distributed load (WUD), shoulder uniformly distributed load (SUD), waist stance foot load (WST), shoulder stance foot load (SST), waist swing foot load (WSW), and shoulder swing foot load (SSW). The paired Hotelling's T-square test was used to compare the experimental conditions. The center of pressure (COP) time series were significantly different for the SUD vs. NL, SST vs. NL, WST vs. NL, and WSW vs. NL comparisons. Significant differences in COP time series were observed for all comparisons between waist vs. shoulder conditions. Overall, these differences were greater when the load was positioned at the shoulders. For the center of mass (COM) time series, significant differences were found for the WUD vs. NL and WSW vs. NL conditions. However, no differences were observed with the load positioned at the shoulders. In conclusion, only asymmetrical loading at the waist produced significant differences, and the higher the extra load, the greater the effects on COP behavior. By contrast, only minor changes were observed in COM behavior, suggesting that the changes in COP (the controller) behavior are adjustments to maintain the COM (controlled object) unaltered.

Postural Control Strategies in Standing With Handrail Support and Active Assistance From Robotic Upright Stand Trainer (RobUST).

In people with severe neuromotor deficits of trunk and lower extremities, regaining balance in standing is often performed in rehabilitation with manual assistance, rigid body supports or by the use of handrails. To investigate and further expand postural control training in standing, we developed a Robotic Upright Stand Trainer (RobUST). In this study, we used RobUST to deliver trunk perturbations while simultaneously providing postural assistive forces on the pelvis in 10 able-bodied adults. Posture control responses with 'pelvic support' was then compared to 'no support' and 'hand supported' standing, with and without assistance from RobUST. We characterize postural imbalance with kinematic displacements and center of pressure (COP) outcomes, such as amplitude and root mean square of the excursions of COP. Surface electromyography (sEMG) was also applied to investigate muscle control. We additionally investigated ground reaction and handrail forces during standing to analyze how postural strategies and muscle mechanisms with 'pelvic support' via RobUST would differ from standing with 'no support' and with the 'handrail support'. Our results show that during perturbations, pelvic assistive support decreased kinematic and COP excursions compared to standing with no support. The pelvic assistance from RobUST showed similar level of COP changes as the use of handrail support but without reducing muscle activity or ground reaction forces. As expected, the maximum level of postural stability was observed when participants used the handrail and received pelvic assistive forces. In conclusion, RobUST demonstrates potential as a training device since it enhances postural balance without significantly removing muscular control mechanisms that are of interest in re-training postural control strategies in standing.

The Effects of Squat Exercises with Vertical Whole-Body Vibration on the Center of Pressure and Trunk Muscle Activity in Patients with Low Back Pain

Background: Patients with low back pain (LBP) experience misalignments in the center of pressure (COP) and muscle imbalances due to frequent onesided posture adjustments to avoid pain.Objectives: To identify the effects of Squat Exercises with Vertical Whole-Body Vibration on the Center of Pressure and Trunk Muscle Activity.Design: Randomized controlled trial.Methods: Thirty LBP patients with an imbalance in the COP were sampled and randomly assigned to an experimental group of 15 patients who under went an intervention involving squat exercises with vertical WBV and a control group of 15 patients who were treated via a walking intervention. As pretests before the interventions, the subjects’ COP was identified by measuring their stability index (ST), and erector spinae, rectus abdominis, transverse abdominis, gluteus medius muscle activity was analyzed by determining the % reference voluntary contraction (%RVC) value using surface electromyography while sit to stand. After four weeks, a post test was conducted to remeasure the same variables using the same methods.Results: Statistically significant differences were found in the ST (P<.01) and trunk muscle (P<.05, P<.001) in the experimental group before and after the intervention. In terms of the differences between the left- and right-side (RL) muscle activity, only the transverse abdominis (TrA) and gluteus medius (GM) exhibited statistically significant increase (P<.05). A comparison of the groups showed statistically significant differences in the TrA with respect to muscle activity (P<.05) and in the RLTrA and RLGM in terms ofthe difference between left- and right-side muscle activity (P<.01).Conclusion: Squat exercises with vertical WBV produced effective changes in the COP of patients with LBP by reducing muscle imbalances through the delivery of a uniform force. In particular, strengthening the TrA and reducing an imbalance in the GM were determined to be important factors in improving the COP.

Assessing the Ergonomic Benefits of a New Adjustable Forklift Backrest

A new forklift backrest has been developed by incorporating adjustability concepts into the design to facilitate comfort to a wide range of users. We have conducted a comparative study between the new and original backrests to assess the effectiveness of design features. Using the phenomenon of restlessness, discomfort of the user was associated with the amount of body movement, where we have used a motion- capture system and a force platform to quantify the individuals’ movement for a wide range of body sizes. Meanwhile, subjective comfort and design feedback were collected using a questionnaire. Our results showed a reduction in the mean torso movement and the maximum center of pressure change of location by 300 and 6 mm, respectively, for the new design. Taking advantage of adjustability feature, the new backrest design exhibited enhanced comfort for longer durations and reduced magnitude of discomfort for a wide range of participants’ body sizes.