Center Of Pressure Movement Research Articles

The effect of uphill and downhill slopes on centre of pressure movement, alignment and shot outcome in mid-handicap golfers

ABSTRACT The aim of the study was to examine changes in centre of pressure (COP) movement, alignment and shot outcome during golf shots from flat, uphill, and downhill slopes by mid-handicap golfers. Twelve male golfers hit balls with a six-iron from the flat and 5° slopes while kinematics and kinetics of the swing were collected. A launch monitor measured performance outcomes. A shift in the COP was found during the backswing when playing on a slope, but disappeared during the downswing. Golfers attempted to align the body perpendicular to the slope at the start of the swing resulting in COP movement towards the lower foot, but were not able to maintain this throughout the swing, like low handicap golfers. There was no significant difference in stance width, but golfers placed the ball closer to the uphill foot on a slope. Ball speed was not significantly affected by the slope, but launch angle and ball spin were. Golfers were more likely to hit shots to the left from an uphill slope and to the right for a downhill slope. No consistent compensatory adjustments in alignment at address were found, with differences in final ball position due to lateral spin.

Undisturbed stance on a double seesaw: Interaction between asymmetries of the center-of-pressure patterns under each foot and weight-bearing

Both center-of-pressure (CP) displacements under each foot and relative body-weight distribution intervene in the production of resultant CP movements. To better understand their respective involvement, a protocol was set up for young healthy individuals consisting in standing on a double seesaw, favoring pitch motions and laying on a dual-force platform. The postural control effects induced by two types of asymmetry, weight-bearing and the CP movement patterns, were investigated. These asymmetries were achieved by associating two seesaws with two different lengths for the radii of the ridges and by requiring specific body-weight distributions. The results indicate that the postural strategies, aimed at controlling anteroposterior sway, are related to the subjects’ capacity to minimize the CP displacements under the less stable support, whatever load is applied. In contrast, the degree of involvement of the more stable support must be viewed as a complement used to secure the appropriate motor output, i.e., the resultant CP movements. Within this objective, both the applied load and the CP amplitudes under the more stable support are taken into account. These data provide additional insights into the compensatory mechanisms between the interactions between the two feet, which are used to produce the adequate resultant CP movements and therefore upright stance control. The specificity of the double seesaw that can induce asymmetric CP patterns and/or asymmetric body-weight distribution makes it a legitimate contender to be used as a rehabilitation device for patients with neurological and/or traumatic diseases.

Influence of age and falls incidence on tau guidance of centre of pressure movement during gait initiation

BackgroundProspective balance control can be assessed in terms of the characteristics of a tau-guidance function that summarizes the velocity profile of Centre of Pressure (CoP) movement during gait initiation. This allows the nature of CoP movement to be assessed on a continuum between controlled ‘soft’- and unstable ‘hard’ CoP-motion gap-closure. Previous research has shown less stable movement patterns with harder closures with increasing age, which makes movements more prone to overshooting and could possibly explain the increasing falls risk with age. Research questionsThe primary research question was ‘what is the relationship between falls incidence and tau-guidance in the mediolateral centre of pressure movements during gait initiation?’ The secondary research question was ‘what are the influences of age and task demands on the variability of tau-guidance characteristics?’. MethodsSixteen young adults and 76 older adults performed 33 gait initiations from a force platform, stepping onto stepping-targets imposing differing task demands. Older participants completed a one-year follow-up screening for falls. An analysis was performed investigating linear relationships between a tau-guidance function and the time-to-closure (tau) of the mediolateral centre of pressure motion-gap with coupling constant K (dependent variable). ResultsGait-related falls during the 12-month follow-up period were associated with higher tau-K values. Furthermore, longer movement preparation time was associated with lower K values, particularly in fallers. Previously-reported age-related increases of the tau-coupling constant values which were found in studies of unconstrained gait initiation were not present in our results. SignificanceThe presence of the targeting task provided a more prescriptive environment compared to unconstrained gait initiation and could explain the absence of age-related changes to the produced K values. Falls incidence was found to be associated with higher values of K, indicating less stable movement. Future studies should investigate the practical implications of these findings for falls prevention.

Noisy Galvanic Vestibular Stimulation Sustainably Improves Posture in Bilateral Vestibulopathy

Patients with bilateral vestibulopathy (BV) suffer from persistent postural imbalance, leading to a marked decrease in quality of life and a higher risk of falls. However, so far, the effective treatments for BV are very limited. We examined whether long-term noisy galvanic vestibular stimulation (nGVS) keeps improving body balance after the cessation of the stimulus in BV patients. Thirteen BV patients received nGVS for 30 min with a lower intensity than the intensity at which they feel any cutaneous sensations, and their postural movement was monitored for 6 h after the stimuli. The same session was repeated at 14-day intervals. Stance tasks on two legs were performed with eyes closed. The velocity of the center of pressure (COP) movement, the area enclosed by the COP movement, and the root mean square of the displacement of the COP were measured. The power spectrum of the COP movement was assessed. Subjective improvement of body balance was graded as worsened (−2), slightly worsened (−1), unchanged (0), slightly improved (+1) and improved (+2) in comparison with that without nGVS. In each session, the velocity of the COP movement was significantly improved for 6 h after the stimulus had ceased (P < 0.01). Concomitantly, the mean frequency of the COP power spectrum was significantly reduced in the anterior-posterior axis (P < 0.05). Subjective symptoms of imbalance were improved during the post-stimulation effect (P < 0.05). nGVS leads to an improvement in body balance that lasts for several hours after the end of the stimulus in BV patients with a reduction in the high-frequency components of their postural movement. This trial was registered with the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMINCTR: UMIN000028054).

Changes in the symmetry of external perturbations affect patterns of muscle activity during gait initiation

BackgroundGait initiation is associated with changes in the steady state and experiencing an external perturbation during initiation of gait could further threaten balance stability. Research questionThe aim of the study was to investigate if changes in the symmetry of the perturbations affect patterns of muscle activity during gait initiation. MethodsEleven young health participants were instructed to stand on the force platform and wait for the instruction of taking a right step, left step or stand still while experiencing a pendulum perturbation applied to the back of both shoulders (symmetric), back of the right shoulder (asymmetric) or no perturbations. Bilateral electromyographic activity (EMG) of dorsal and ventral muscles, moments of the pendulum release and perturbation impact, center of pressure (COP) displacements and pelvic movements were recorded and analyzed before and after the onset of the perturbation. ResultsTaking the right/left step in presence of symmetric perturbation did not affect the temporal sequence of COP and pelvic movements. The onset of COP and pelvic movement occurred before the perturbation impact at the shoulder levels. The factors of step and perturbation did not significantly affect integrals of bilateral muscles at the pendulum release. After the pendulum release, ventral and dorsal EMG integrals of the trunk, thigh, and shank segments increased or decreased corresponding to the swing and stance leg. Changes in muscle activities were also associated with the symmetric or asymmetric perturbations before and after the perturbation impact. SignificanceThe outcome of the study provides information about strategies used to coordinate the activity of muscles while body perturbations are induced during gait initiation.

Comparison of gait parameters between drug-naïve patients diagnosed with multiple system atrophy with predominant parkinsonism and Parkinson's disease

Even though gait symptoms are prominent in patients diagnosed with multiple system atrophy with predominant parkinsonism (MSA-P) compared with Parkinson's disease (PD), the gait patterns of MSA-P were not clearly elucidated. We investigated postural instability and gait disturbances in MSA-P compared with PD. We enrolled 34 drug-naïve patients with PD and 26 with MSA-P, and 18 normal controls in this study. Parkinsonism was evaluated by the Unified Parkinson's disease rating scale (UPDRS) part 3 and cognition was assessed with mini-mental status exam (MMSE). All the enrolled subjects underwent Pedoscan and GAITRite to objectively measure postural stability and gait. We compared the results of posturography and gait analysis among 3 groups, and performed correlation analysis of gait parameters with MMSE, UPDRS part 3 and posturography results. No difference was detected in demographic and clinical variables, except tremor sub-score of UPDRS part 3, urinary symptoms and orthostatic hypotension. MSA-P patients showed larger total anterior-posterior and lateral movement of centre of pressure (COP), and widened base of support than PD patients. In correlation analysis, MMSE score, axial sub-score of UPDRS part 3 and lateral movement of COP were correlated with gait parameters in PD patients, while only axial sub-score was associated in MSA-P patients after controlling for age, sex, height, body weight, education year, and disease duration. Even at an early stage, MSA-P patients demonstrated more postural instability and gait disturbance compared with PD patients, and the related factors with gait disturbance in PD and MSA-P might be different.

Postural control before and after cerebrospinal fluid shunt surgery in idiopathic normal pressure hydrocephalus

ObjectivesThis study aimed to confirm whether cerebrospinal fluid (CSF) shunting for idiopathic normal-pressure hydrocephalus (iNPH) improves postural instability, and to investigate the relationship between postural control and gait ability. Patients and methodsTwenty-three iNPH patients and 18 age-matched healthy controls (HC) were examined using the timed up and go (TUG) test and a force platform for calculating the center of pressure (COP) trajectory during voluntary multidirectional leaning and quiescent standing. We determined the patients’ TUG values and COP trajectories before and after shunt surgery. ResultsPostural sway was greater in iNPH patients before shunt surgery and the TUG value was lower in iNPH patients before shunt surgery than in HC. Voluntary COP movements were significantly improved in iNPH patients at 1 week post-surgery, but no significant changes in quiescent standing were found between pre- and post-surgery. Significant correlations were found between the TUG value and voluntary COP movements in iNPH patients before and after surgery, but no significant correlations were observed between the TUG value and quiescent standing. ConclusionOur results indicate that CSF shunting in iNPH patients may improve voluntary postural control and reduce the risk of falling. Impaired voluntary COP control in iNPH patients may reflect the underlying pathophysiological mechanisms of balance disturbance in iNPH.

Graded forward and backward walking at a matched intensity on cardiorespiratory responses and postural control

BackgroundWhile several studies compare backward walking (BW) and forward walking (FW) in terms of heart rate (HR) and rating of perceived exertion (RPE), workload (VO2) was not matched to control for intensity levels (Hooper et al. [1]). Moreover, acute effects of inclined BW on postural control and ankle musculature has not been investigated. This study was designed to compare cardiovascular, metabolic and perceptual responses, changes in center of pressure (COP) motion, and muscle activation of tibialis anterior (TA) and gastrocnemius (GM) to control quiet stance posture immediately following inclined BW and FW at a matched intensity. MethodsSeventeen healthy young adults completed three lab sessions 7–14 days apart. Session one, maximal oxygen consumption (VO2max) was measured using open-circuit spirometry for each participant. Session two, participants performed BW for 15-min. Session three, participants performed FW for 15-min at matched intensity of BW. Surface electromyography (SEMG) measured the muscular activity of the TA and GM during bilateral stance on a force plate for 30 s prior to and immediately following BW and FW under both eyes open (EO), and eyes closed (EC) conditions. ResultsHR, VCO2, RER and RPE were significantly greater during BW compared to FW. Increased muscle activation and COP motion was elicited immediately following BW compared to FW under EO and EC. ConclusionResults of this study indicate BW requires greater cardiovascular, metabolic, perceptual and neuromuscular demands than FW, which may cause postural instability particularly to those with compromised balance. While there are benefits to BW in rehabilitation settings, these factors should be considered when prescribing BW for training and/or rehabilitation exercise program (Duffell et al. [2], Warnica et al. [3]).

O 097 – Predictors of midfoot break in children with cerebral palsy and flatfeet

Degenerative lumbar diseases (DLDs) are characterized by motor functional deficits and postural instability. In this study, we investigated the differences in the trunk muscle responses to postural control between the presurgical DLD patients and healthy individuals while performing the static and perturbed balance tasks.Thirty-five DLD patients (aged 61.1 ± 8.0 years) and thirty-five asymptomatic controls (aged 62.9 ± 3.7 years) participated in this study. All participants stood on a force plate and performed the quiet standing (QS) and in situ weight-lifting (WL) tasks. The participants’ performance in the QS task was tested under the eyes-open, eyes-closed, wide-base, and narrow-base conditions. Center of pressure (CoP) movements and electromyography of the erector spinae (ES) were recorded. The Mann–Whitney U test was applied for statistical analysis.The DLD group showed a significantly greater CoP movements and muscle activations during the QS task. Nevertheless, smaller CoP movements were noted during the WL task in the DLD group. Under the eyes-closed and narrow-base conditions, the DLD group showed even higher muscle activations and CoP movements.The DLD patients demonstrated a poor postural control ability and tended to rely on the visual feedback and wide-base standing posture. A rigid and restricted posture was also adopted during the perturbed WL task. A high level of ES activation was required to maintain their postural steadiness. This study reveals an aberrant pattern of postural control and trunk muscle activations in symptomatic DLD patients which potentially contributes to the development of beneficial rehabilitation programs.

Postural stability and trunk muscle responses to the static and perturbed balance tasks in individuals with and without symptomatic degenerative lumbar disease

BackgroundDegenerative lumbar diseases (DLDs) are characterized by motor functional deficits and postural instability. In this study, we investigated the differences in the trunk muscle responses to postural control between the presurgical DLD patients and healthy individuals while performing the static and perturbed balance tasks. MethodsThirty-five DLD patients (aged 61.1 ± 8.0 years) and thirty-five asymptomatic controls (aged 62.9 ± 3.7 years) participated in this study. All participants stood on a force plate and performed the quiet standing (QS) and in situ weight-lifting (WL) tasks. The participants’ performance in the QS task was tested under the eyes-open, eyes-closed, wide-base, and narrow-base conditions. Center of pressure (CoP) movements and electromyography of the erector spinae (ES) were recorded. The Mann–Whitney U test was applied for statistical analysis. ResultsThe DLD group showed a significantly greater CoP movements and muscle activations during the QS task. Nevertheless, smaller CoP movements were noted during the WL task in the DLD group. Under the eyes-closed and narrow-base conditions, the DLD group showed even higher muscle activations and CoP movements. SignificanceThe DLD patients demonstrated a poor postural control ability and tended to rely on the visual feedback and wide-base standing posture. A rigid and restricted posture was also adopted during the perturbed WL task. A high level of ES activation was required to maintain their postural steadiness. This study reveals an aberrant pattern of postural control and trunk muscle activations in symptomatic DLD patients which potentially contributes to the development of beneficial rehabilitation programs.

Detraining effects of regular Tai Chi exercise on postural control ability in older women: A randomized controlled trial

Background/ObjectiveThis study aimed to investigate the training and detraining effects of Tai Chi (TC) on postural control ability in single leg stance (SLS) by conducting a single-blind randomized controlled trial. MethodForty-eight older women were randomly divided into the TC, brisk walking (BW), and control(C) groups by using computer-generated program. The participants completed a 16-week intervention training and 8-week detraining program. Postural control ability in SLS was tested at the baseline, 16 t h, 20 t h, and 24 t h weeks. The primary outcomes included single-leg stance time (Time) and secondary outcomes included maximal displacement of the center of pressure (COP) in the anterior–posterior (AP) direction (D-ap), maximal displacement of the COP in the medial–lateral (ML) direction (D-ml), total length of the COP trajectories (Lng), and 95% confidence ellipse area of the COP movements (area), mean AP total excursion velocities (V-ap), and mean ML total excursion velocities (V-ml). ResultsSignificant within-group difference compared with the baseline and between-groups difference compared with control group were found at 16 t h, 20 t h, and 24 t h weeks in the TC group and at the 16 t h and 20 t h weeks in the BW group in all the primary and secondary outcomes. Most of secondary outcomes including Lng, D-ml, V-ml, Area increased significantly at the 24 t h week compared with that at the 16 t h week in BW group. ConclusionsTC was effective in improving postural control ability and maintaining intervention gains, and was recommended as an appropriate exercise to prevent falls in the older adults.

Exploring the relationship between stability and variability of the centre of mass and centre of pressure

BackgroundThere are competing perspectives in the literature regarding the role of movement variability in quiet standing and balance control. Some view high variability as indicative of poor balance control and a contributor to increased fall risk, whereas others view variability as beneficial in providing sensory information that aids balance control. Research questionThis study aimed to help to clarify the role of variability in balance control by testing two competing hypotheses: that increased variability would lead to instability, or that increased variability would improve stability, where stability is defined as the ability to respond to a perturbation. MethodsFourteen healthy young adults (20–35 years old) were recruited. Participants experienced postural perturbations of varying magnitudes, delivered via sudden backward movement of the support surface. Magnitudes of postural perturbation were chosen such that both step and no-step responses could be observed at each magnitude. Variability in the centre of mass and centre of pressure movement was measured for 10 s prior to the postural perturbation. Multiple regression was used to determine if movement variability predicted step responses when controlling for perturbation magnitude, trial order, and margin of stability at perturbation onset. ResultsLower variability in medio-lateral centre of mass and centre of pressure position, and lower variability in medio-lateral centre of pressure velocity were related to increased odds of stepping in response to the perturbation (p-values ≤0.001). SignificanceThis study provides support for the hypothesis that, at least for relatively low variability values, increased centre of pressure and mass movement variability improves stability. Specifically, increasing movement of the centre of pressure and mass in the medio-lateral direction may help to preserve stability in the antero-posterior direction by providing the central nervous system with information about the antero-posterior centre of mass across a wide range of medio-lateral positions.

Age and gymnastic experience effects on sensory reweighting processes during quiet stand

BackgroundThe relative contribution of sensory inputs to control balance while standing is dynamically adjusted. These sensory reweighting processes could be impacted by age and sport expertise capabilities, especially when the sport emphasizes equilibrium like artistic gymnastics. Research questionThe aim of this study was to explore the sensory reweighting processes to adjust standing posture in children and adults with different gymnastic expertise (gymnasts, G, and non-gymnast, NG). MethodsAll participants were asked to stand quietly on a force plate in two visual conditions (eyes open, EO, and eyes closed, EC). Within a trial, proprioception was altered with two vibrators strapped at the Achilles tendon level. The center of pressure (COP) displacements in the anterior-posterior and medio-lateral directions were calculated and normalized by the base of support. The effect of vibration application was characterized by the COP speed, maximal posterior displacement and the time when it occurred. The effect of vibration removal was depicted by the time between the motor switched off and the achievement of balance values similar to baseline and the COP speed and movement units performed during this time. ResultsG children presented shorter posterior displacement during vibrations, needed less time to recover initial balance, and produced less movements units than NG children. In general, adults and EO showed better reweighting responses than children and EC, respectively. SignificanceThese results suggest that age could have a positive effect on reweighting processes and that gymnastic experience may benefit the development of proprioceptive reweighting processes in children but not in adults.

Center of Pressure Motion After Calf Vibration Is More Random in Fallers Than Non-fallers: Prospective Study of Older Individuals.

Aging is associated with changes in balance control and elderly take longer to adapt to changing sensory conditions, which may increase falls risk. Low amplitude calf muscle vibration stimulates local sensory afferents/receptors and affects sense of upright when applied in stance. It has been used to assess the extent the nervous system relies on calf muscle somatosensory information and to rapidly change/perturb part of the somatosensory information causing balance unsteadiness by addition and removal of the vibratory stimulus. This study assessed the effect of addition and removal of calf vibration on balance control (in the absence of vision) in elderly individuals (>65 years, n = 99) who did (n = 41) or did not prospectively report falls (n = 58), and in a group of young individuals (18–25 years, n = 23). Participants stood barefoot and blindfolded on a force plate for 135 s. Vibrators (60 Hz, 1 mm) attached bilaterally over the triceps surae muscles were activated twice for 15 s; after 15 and 75 s (45 s for recovery). Balance measures were applied in a windowed (15 s epoch) manner to compare center-of-pressure (CoP) motion before, during and after removal of calf vibration between groups. In each epoch, CoP motion was quantified using linear measures, and non-linear measures to assess temporal structure of CoP motion [using recurrence quantification analysis (RQA) and detrended fluctuation analysis]. Mean CoP displacement during and after vibration did not differ between groups, which suggests that calf proprioception and/or weighting assigned by the nervous system to calf proprioception was similar for the young and both groups of older individuals. Overall, compared to the elderly, CoP motion of young was more predictable and persistent. Balance measures were not different between fallers and non-fallers before and during vibration. However, non-linear aspects of CoP motion of fallers and non-fallers differed after removal of vibration, when dynamic re-weighting is required. During this period fallers exhibited more random CoP motion, which could result from a reduced ability to control balance and/or a reduced ability to dynamically reweight proprioceptive information. These results show that non-linear measures of balance provide evidence for deficits in balance control in people who go on to fall in the following 12 months.

Blood pressure change does not associate with Center of Pressure movement after postural transition in geriatric outpatients

BackgroundOrthostatic hypotension (OH), a blood pressure drop after postural change, is associated with impaired standing balance and falls in older adults. This study aimed to assess the association between blood pressure (BP) and a measure of quality of standing balance, i.e. Center of Pressure (CoP) movement, after postural change from supine to standing position in geriatric outpatients, and to compare CoP movement between patients with and without OH.MethodsIn a random subgroup of 75 consecutive patients who were referred to a geriatric outpatient clinic, intermittent BP measurements were obtained simultaneously with CoP measurements in mediolateral and anterior-posterior direction directly after postural change during 3 min of quiet stance with eyes open on a force plate. Additional measurements of continuous BP were available in n = 38 patients. Associations between BP change during postural change and CoP movement were analyzed using Spearman correlation. Mann-Whitney-U tests were used to compare CoP movement between patients with OH and without OH, in which OH was defined as a BP drop exceeding 20 mmHg of systolic BP (SBP) and/or 10 mmHg of diastolic BP (DBP) within 3 min after postural change.ResultsOH measured intermittently was found in 8 out of 75 (11%) and OH measured continuously in 22 out of 38 patients (57.9%). BP change did not associate with CoP movement. CoP movement did not differ significantly between patients with and without OH.ConclusionsResults do not underpin the added value of CoP movement measurements in diagnosing OH in a clinical setting. Neither could we identify the role of CoP measurements in the understanding of the relation between OH and impaired standing balance.

Differences in Lower Limb Muscle Activation and Centre of Pressure Movement Between Expert Workers and Novices in Simulated Maritime Environments

OCCUPATIONAL APPLICATIONS Better understanding of lower limb muscle activations and habituation processes has implications for injury prevention. This study examined the influence of repeated exposures to simulated wave motions on lower limb muscle activity. Our findings suggest that, at least while standing, novice maritime workers can quickly adapt their lower extremity muscle activity and, to a lesser extent, their center of pressure movement, so that is similar to expert maritime workers. These decreases in muscle activations with repeated exposures suggest that individuals can adapt rapidly to the motions to decrease muscle fatigue and the risk of falling. Such information should therefore be considered when developing ergonomic interventions for maritime occupations such as ship design and training for new workers.TECHNICAL ABSTRACT Background: Work in moving environments, such as maritime workplaces, exposes workers to unique neuromuscular control challenges that may increase risk of falls or fatigue-related injury. Purpose: The purpose of this study was to determine if muscle activations differ based on previous experience working in a moving environment and/or with repeated exposure to the same motions. Methods: Twelve individuals with no maritime work experience, and 14 individuals with maritime work experience, were exposed to five 5-minute trials of simulated maritime motion. Electromyography (EMG) was collected bilaterally from several lower-extremity muscles and center of pressure was collected using a pressure mat over the full duration of all of the trials. EMG data were normalized to maximal voluntary isometric contractions (MVICS) collected before the trials, and then compared between groups and trials. Results: Muscle activation in both groups significantly increased with motion exposure, however the activation amplitudes were lower in the experienced (346% increase) vs. the novice group (542% increase). With repeated exposure to the five motion trials, muscle activations for all individuals gradually decreased from trial 1 (∼5–15%MVIC) to trial 5 (∼1.5–4.5%MVIC).Conclusions: While all individuals demonstrated adaptations with repeated exposures, those with experience working in maritime environments adopted postural responses that required substantially less activation of the lower limb muscles. This difference may be due, at least in part, to these individuals having adapted postural control strategies to optimize stability. The decrease in muscle activation observed with repeated exposure to the motion profile suggests that individuals can adapt rapidly to the destabilizing nature of the motion profiles, implying that they are learning to adopt more efficient postural control strategies.

Reactive balance control in older adults with diabetes

Diabetes mellitus is a major health problem for older adults worldwide and could be associated with impaired ability to recover balance after postural disturbances. This study compared reactive balance control in three groups of adults, young (YA), healthy non-diabetes older (nonDM-OA) and diabetes older (DM-OA). Twenty participants in each group completed a series of vision, plantar cutaneous sensitivity, grip power and lower limb strength tests. In the reactive balance test, participants stood on a force platform and used the dominant hand to pull the handle of a cord that could be suddenly released to create an imbalancing force. The anteroposterior (AP) and mediolateral (ML) motion of the center of pressure (COP) immediately after the sudden release was calculated to represent the level of imbalance experienced by the participants. Regression analysis entering big toe plantar sensitivity and grip power as independent variable was conducted for COP range for the three groups separately. The results showed that, except for the knee extensor, DM-OA had significantly poorer muscle strength and plantar sensitivity, and greater COP ML motion than YA and nonDM-OA. DM-OA also had significantly greater COP AP motion than YA. Grip power alone and together with plantar sensitivity explained a significant amount of variance in the AP and ML COP motion respectively (r2 = 0.334 and 0.582, respectively) for DM-OA. These findings indicated that diabetes in older adults was associated with declines in reactive balance control, and these changes may be related to muscle weakness and plantar insensitivity.

Design and adaptive balance control of a biped robot with fewer actuators for slope walking

Although reducing the number of actuators in mobile robots contributes to weight saving and results in high efficiency or damage reduction in the event of an accident such as falling over, ideally it should not degrade the robot’s performance and functionality. In this study, we propose a new biped mechanism that reduces the number of actuators in a robot without sacrificing its ability to walk adaptively on slopes. We address two issues from both the mechanical and the control viewpoints that are required to achieve straight walking on slopes. For the biped mechanism, we studied the required degrees of freedom of the biped robot and then proposed an actuation mechanism for the hip joint structure. Subsequently, we designed and constructed a biped robot with six actuators, including two actuators for each ankle, no knees, and two actuators for the hip joint structure. For control, we applied feedback from the center of pressure (CoP) of the ground reaction forces in addition to gravity compensation and discussed the stability of CoP movement. Experiments conducted using the constructed biped robot with fewer actuators demonstrated the viability of the proposed mechanism in terms of walking on slopes and the effectiveness of the proposed control concept, which introduces adaptability to the biped robot.

Alterations in the ability to maintain balance as a result of stochastic resonance whole body vibration in women.

PurposeA vertical posture makes it difficult to maintain balance especially in the elderly. Loss of balance leads to falls and injuries. In the present study, we evaluated whether balance maintenance can be improved with the use of stochastic resonance whole body vibration (SR-WBV).MethodsAn examination of balance, involving 187 women aged 19–74 years, was conducted using double-plate posturography pre and post SR-WBV. The SR-WBV trainings were performed using the SRT Zeptor Medical-plus noise device. The entire study lasted 6 weeks, with a total of 12 training sessions, each consisting of nine 45 second series, with a 45 second pause between them.ResultsPost SR-WBV there was a reduction in the value of: the resultant mean velocity (MV) of the movement of COP (centre of pressure) for both lower limbs (B) and in the right lower limb (R) during the test with eyes closed (EC), the mean velocity and mean amplitude (MA) of the movement of COP along the x-axis (ML) of the left lower limb (L) during the test with eyes open (EO) and closed and some additional parameters. Negative correlations between age/index of improvement of MV-EC-B, MV-EC-L and MVML-EC-L, and BMI/index of improvement of MV-EC-B, MVML-EC-B appeared. Height correlated positively with the index of improvement of MV-EC-B and MVML-EC-B.ConclusionsAs a result of SR-WBV, the left leg is more stable along the x-axis and the disproportion between the stability of both legs is reduced. Consequently, body stability is higher. The SR-WBV is more effective in younger, taller and slimmer women. SR-WBV parameters should be optimized so that the training is more beneficial for elderly and shorter women, and for women with a higher BMI.

Quantifying center of pressure variability in chondrodystrophoid dogs

The center of pressure (COP) position reflects a combination of proprioceptive, motor and mechanical function. As such, it can be used to quantify and characterize neurologic dysfunction. The aim of this study was to describe and quantify the movement of COP and its variability in healthy chondrodystrophoid dogs while walking to provide a baseline for comparison to dogs with spinal cord injury due to acute intervertebral disc herniations. Fifteen healthy adult chondrodystrophoid dogs were walked on an instrumented treadmill that recorded the location of each dog’s COP as it walked. Center of pressure (COP) was referenced from an anatomical marker on the dogs’ back. The root mean squared (RMS) values of changes in COP location in the sagittal (y) and horizontal (x) directions were calculated to determine the range of COP variability.Three dogs would not walk on the treadmill. One dog was too small to collect interpretable data. From the remaining 11 dogs, 206 trials were analyzed. Mean RMS for change in COPx per trial was 0.0138 (standard deviation, SD 0.0047) and for COPy was 0.0185 (SD 0.0071). Walking speed but not limb length had a significant effect on COP RMS. Repeat measurements in six dogs had high test retest consistency in the x and fair consistency in the y direction. In conclusion, COP variability can be measured consistently in dogs, and a range of COP variability for normal chondrodystrophoid dogs has been determined to provide a baseline for future studies on dogs with spinal cord injury.