Center Of Pressure Movement Research Articles

Strategies for equilibrium maintenance during single leg standing on a wobble board

The aim of this study was to identify and compare movement strategies used to maintain balance while single leg standing on either a firm surface (FS) or on a wobble board (WB). In 17 healthy men, retroreflective markers were positioned on the xiphoid process and nondominant lateral malleolus to calculate trunk and contralateral-leg excursion (EXC) and velocity (VEL), and center of pressure (CoP) EXC and VEL during FS on a force platform. From the WB test, standing time (WBTIME) was determined and the board's angular EXC and VEL were calculated from four markers on the WB as surrogate measures for CoP dynamics. Electromyographic average rectified values (ARV) from eight leg and thigh muscles of the supporting limb were calculated for both tasks. WB ARV amplitudes were normalized with respect to the value of FS ARV and presented significantly higher peroneus longus and biceps femoris activity (p<0.05). WB standing time was correlated to trunk sagittal plane velocity (r=−0.73 at p=0.016) and excursion (r=−0.67 at p=0.03). CoP and WB angular movement measures were weakly and not significantly correlated between tasks. This lack of correlation indicates that WB balance maintenance requires movement beyond the ankle strategy as described for the FS task. WB standing likely demands different biomechanical and neuromuscular control strategies, which has immediate implications for the significance of WB tests in contrast to FS balance tests. Differences in control strategies will also have implications for the understanding of mechanisms for rehabilitation training using such devices.

POSTURAL BALANCE AFTER SURGICAL DECOMPRESSION AND STABILIZATION IN PATIENTS WITH DEGENERATIVE DYSTROPHIC DISEASES OF THE LUMBAR SPINE

Objective. To study characteristics of postural balance in patients with degenerative dystrophic diseases of the lumbar spine in the early postoperative period and between 8 and 12 months after surgery. Material and Methods . The study included the assessment of stabilometric parameters of postural balance, which were measured using Romberg test with eyes open/closed in 16 patients aged 26 to 60 years. All patients underwent decompression and stabilization surgery for compression and complex regional pain syndromes of degenerative disc disease of the lumbar spine. Results . Visual control used by patients in performing stabilometric test with eyes open made it possible to reduce significantly the following parameters in 8-12 months after surgery: oscillatory movements of the center of pressure (CoP) in the frontal and sagittal planes by more than 1.8 times, the sum of CoP displacements by 1.57 times, the average speed of CoP displacement by 1.57 times, and the area of oscillations by 3 times. At the same time predominantly sagittal direction of the CoP movement was preserved that corresponds to the normal postural balance of the body in space. Conclusion . Formation of the stable position of the body in space occurs at 8-12 months after surgical treatment only with the involvement of visual control. This necessitates the inclusion of the complexes of therapeutic exercises for rehabilitation of patients.

Effect of lower limb preference on variability of centre of pressure movement during gait

Background: Centre of pressure (COP) movement variability, as an example of 'end-point' variability (stability), may be one of the indicators that can assess the functional gait asymmetry caused by foot preference in relation to fall risk. Objective: The aim of this study was to investigate the possible differences in COP movement variability during the stance phase of gait caused by both aging and lower limb preference. Methods: Two groups of females participated in this study: Younger (n = 25, age 22.2 ± 1.8 years) and Middle-aged (n = 25, age 56.6 ± 4.9 years). COP movement and ground reaction forces during gait at self-selected speed were recorded using two force platforms. The standard deviations of the medial-lateral and anterior-posterior COP displacements in four subphases: loading response (LR), midstance (MSt), terminal stance (TSt) and pre-swing (PSw) were assessed. Results: The observed variables indicated significantly higher mean values in almost all cases in subphases LR and PSw in comparison with MSt and TSt. When comparing preferred and non-preferred limb, the preferred limb showed greater variability in medial-lateral direction during LR and less variability in anterior-posterior direction during PSw. In the Younger group, greater variability was found on preferred limb in anterior-posterior direction during LR. When assessing age-related differences all significant cases showed higher variability in the Middle-aged group. Conclusions: The results suggest that COP movement variability is less on the non-preferred limb during weight acceptance and on the preferred limb during propulsion.

The Study of Fluorescent Chemicals for Fingerprint Development

Center of pressure (COP) movement during sitting on an unstable chair can be used to represent static trunk postural control. Theoretically, healthy individuals with intact trunk proprioception should have similar COP movement between eye-open and eye-closed conditions regardless of visual feedback. The custom software program has been developed to investigate COP movement in this group of participants. However, test-retest reliability of COP measurement has not been established. Therefore, the purposes of this study were to determine test-retest of COP measurement, and compare area of COP movement (aCOP) between eye-open and eye-closed conditions in healthy individuals. Material and Method: Five healthy individuals (age = 26.6 ± 5.41 years; BMI = 21.46 ± 2.48kg/m2; 4 males) performed 30-second seated balance with eye-open (2 trials) and eye-closed (2 trails). The aCOP represents trunk postural control (greater area represents poor trunk postural control). Intra-class correlation coefficient (ICC) was used to determine test-retest reliability (ICC3, 1). 90% confidence minimum detectable change (MDC) was calculated to establish a degree of measurement error. Wilcoxon's signed rank test was used to compare aCOP between two conditions. Results: ICC3, 1 was 0.76 and 0.26, and MDC were 14.94 and 31.76 mm. in eye-open and eye-closed, respectively. This finding indicates moderate to good test-retest reliability of instrument for collecting COP movement. No significant difference was found between two conditions. Conclusion: The instrument in this study could be used to investigate trunk postural control in eye-open condition, but might be currently limited when using in eye-closed condition. The result from comparison between conditions suggests trunk proprioception may help maintaining balance during seated balance in healthy individuals. However, patients with low back pain suspected of having impaired trunk proprioception may demonstrate significant difference between these two conditions. Therefore, future study is needed to provide biomechanical evidence supporting this hypothesis.

Three-Month Test-Retest Reliability of Center of Pressure Motion During Standing Balance in Individuals with Multiple Sclerosis.

Balance impairment and an increased rate of falls are commonly reported in individuals with multiple sclerosis (MS). Force platform-generated center of pressure (COP) metrics have previously been recommended as an outcome measure to quantify balance deficits and distinguish between fallers and nonfallers in MS. Information is limited regarding the preservation of postural control in individuals with MS over extended time frames in the absence of an intervention. This report examines the test-retest reliability and magnitude of change of COP motion during standing balance over 3 months. Twenty individuals with MS and a history of falling underwent testing on two occasions 3 months apart in the absence of an intervention. On both occasions, participants completed two 30-second trials of three conditions: eyes open, eyes closed, and eyes open with concurrent cognitive challenge (dual task). Measures of COP area, velocity, and temporal structure were calculated and included in the reliability analysis. The COP metrics displayed fair-to-excellent reliability over 3 months without an intervention. Reliability was maintained across the three commonly used balance conditions. These results offer insight into the reliability of COP measures over a 3-month period in MS and can inform the use of COP metrics for future study design (eg, sample size estimates) and balance outcome assessment during randomized controlled trials and fall-prevention studies in individuals with MS.

Three-Month Test-Retest Reliability of Center of Pressure Motion During Standing Balance in Individuals with Multiple Sclerosis

Three-Month Test-Retest Reliability of Center of Pressure Motion During Standing Balance in Individuals with Multiple Sclerosis

Effect of neck muscles and gluteus medius vibrations on standing balance in healthy subjects

Muscle vibration can be used to improve the center of pressure (CoP) shift. Several muscle sites have been used for various diseases without that we know their respective interest. To compare the effects and post-effects of neck muscle vibrations (NMV) and gluteus medius vibrations (GMV) on balance in healthy subjects Thirteen healthy subjects, mean: 23 years, right handed were tested on posturography, closed eyes, in standing position. They received successively left NMV and right GMV in a randomized order. The variation of the deviation of CoP on the médiolatéral plane was evaluated under vibration stimulation (5 min), at the end of the vibration and 5 minutes after. GMV induce a CoP movement to left side (9 responders) (mean: 5.21 mm; SD: 4.79; P = 0.003). At the end of the vibration, the effect remained significant (mean: 4.73, SD: 4.02; P = 0.001) and after 5 minutes, the subjects restored their initial balance (mean: 1.25, SD: 6.82; P = 0.33). For NMV, a movement toward left side was observed only in 5 subjects but this deviation seemed to be maintained at 5 min. The CoP deviation was not significant during ( P = 1), immediately after ( P = 0.72), and after 5 minutes of NMV ( P = 0.89). GMV cause a lateral shift in 70% of the subjects of nearly 5 mm. The effect of NMV was lower and less constant (only 5 responders) but sustainable. This could be explained by a sensorimotor peripheral action for GMV while NMV would involve high level body representation in space.

Time scale dependence of the center of pressure entropy: What characteristics of the neuromuscular postural control system influence stabilographic entropic half-life?

The center of pressure (COP) movement in studies of postural control reveals a highly regular structure (low entropy) over short time periods and a highly irregular structure over large time scales (high entropy). Entropic half-life (EnHL) is a novel measure that quantifies the time over which short-term temporal correlations in a time series deteriorate to an uncorrelated, random structure. The current study suggested and tested three hypotheses about how characteristics of the neuromuscular postural control system may affect stabilometric EnHL: (H1) control system activity hypothesis: EnHL decreases with increased frequency of control system interventions adjusting COP motion; (H2) abundance of states hypothesis: EnHL decreases with increased number of mechanically equivalent states available to the postural system; and (H3) neurologic process hierarchy hypothesis: EnHL increases if postural control functions shift from the spinal level to the motor cortex. Thirty healthy participants performed quiet stance tests for 90 s in 18 different conditions: stance (bipedal, one-legged, and tandem); footwear (bare foot, regular sports shoe, and rocker sole shoes); and simultaneous cognitive task (two-back working memory task, no challenge). A four-way repeated-measures ANOVA revealed significant changes in EnHL for the different stance positions and for different movement directions (medio-lateral, anterior-posterior). These changes support H1 and H2. Significant differences were also found between rocker sole shoes and normal or barefoot standing, which supports H3. This study contributes to the understanding of how and why EnHL is a useful measure to monitor neuromuscular control of balance.

Body Sway as a Possible Indicator of Fatigue in Clerical Workers.

BackgroundFatigue has a strong impact on workers' performance and safety, but expedient methods for assessing fatigue on the job are not yet available. Studies discuss posturography as an indicator of fatigue, but further evidence for its use in the workplace is needed. The purpose of the study is to examine whether posturography is a suitable indicator of fatigue in clerical workers.MethodsThirty-six employees (Ø 34.8 years, standard deviation = 12.5) participated in postural tasks (eyes open, eyes closed, arm swinging, and dual task) in the morning and afternoon. Position of their center of pressure (COP) was registered using a Nintendo Wii Balance Board and commercial software. From registered COP time series, we calculated the following parameters: path length (mm), velocity (mm/s), anterior–posterior variance (mm), mediolateral variance (mm), and confidence area (mm2). These parameters were reduced to two orthogonal factors in a factor analysis with varimax rotation.ResultsStatistical analysis of the first factor (path length and velocity) showed a significant effect of time of day: COP moved along a shorter path at a lower velocity in the afternoon compared with that in the morning. There also was a significant effect of task, but no significant interaction.ConclusionData suggest that postural stability of clerical workers was comparable in the morning and afternoon, but COP movement was greater in the morning. Within the framework of dynamic systems theory, this could indicate that the postural system explored the state space in more detail, and thus was more ready to respond to unexpected perturbations in the morning.

Changes in Postural Control following Inclined Backward and Forward Treadmill Walking.

In recent years, backward walking has been shown to provide neuromuscular and cardiovascular benefits and postural control improvements in school-aged children. However, the immediate impact of backward walking is not known. PURPOSE: To determine the impact that backward and forward walking on a treadmill at a matched intensity had on postural motion. METHODS: Ten participants, five males and five females (age = 19.8 ± 0.9 yr, height = 172.0 ± 8.0 cm, weight = 76.1 ± 13.9 kg, BMI = 25.6 ± 3.7 kg·m-2, VO2max = 44.86 ± 9.40 ml·kg-1·min-1) completed three lab sessions, seven to fourteen days apart. In session one maximal oxygen consumption (VO2max) was established for each participant and familiarization of standing on the force plate with an Airex ®pad. Session two consisted of a 15-minute backward walking trial (BWT) at 67 m·min-1 and 10% grade. Session three consisted of a 15-minute forward walking trial (FWT) at an intensity similar to that of BWT. In the second and third sessions, center of pressure (COP) motion was recorded while standing on a force plate for 30s prior to and immediately following walking sessions under eyes open (EO) and eyes closed (EC) conditions. RESULTS: The results of the postural sway and exertion measures are in the table below:Table: No title available.Mean ± SD; *p<0.05 compared to FWT, p< 0.05 compared to EO, p< 0.05 compared to baseline. ApEn = Approximate Entropy, EO = eyes open, EC = eyes closed. CONCLUSION: Backward walking compared to forward walking elicited increases in the total amount of COP motion (path length, mean A-P/M-L) regardless of the vision condition. Consistent with the measures of exertion, this may indicate that backward walking placed a greater demand on the immediate postural responses compared to forward walking as a result of different activation levels of the ankle musculature involved in backward walking.

The immediate effects of an intervention based on the Bobath concept on balance and gait in people with multiple sclerosis

Background: The Bobath concept is a physiotherapy approach widely used in the treatment of Multiple sclerosis (MS). Interventions involving treatment of the foot and ankle are a strong focus of the Bobath concept, with the aim of improving postural control at the dynamic interface between the person and the base of support. We were unable to identify any studies investigating the effect of these interventions on postural control, or studies assessing postural control in higher level balance tasks, such as single leg stance, in people with MS. Purpose: (1) To investigate the immediate change after a single intervention based on the Bobath concept on people with MS. (2) To compare the balance and gait of people with MS with healthy controls. Methods: Participants in the study were people with MS with self reported gait and balance deficits. Exclusion criteria included inability to stand in single leg stance (SLS) on the most impaired leg. Participants were age and gender matched with healthy controls. Balance was assessed by ground reaction forces (GRF) and centre of pressure movements during SLS, and two clinical tests, the Lateral Reach Test (LRT) and the Four Square Step Test (FSST). Gait was evaluated by GRF, ankle kinematics and spatiotemporal measures. The Bobath based intervention focused on mobilising and activating the most impaired foot and ankle in sitting. The treatment was tailored for each individual to address their specific impairments of the foot and ankle. Key components were provision of sensory information, stretch of intrinsic muscles of the foot to selectively activate the foot, improving alignment of the talo- crural joint and activation of gastrocnemius. Eleven people with MS were recruited to the study and 11 healthy controls. Baseline measures in the MS group showed significantly greater vertical GRF variability (p = 0.008) during SLS, less distance reached on the LRT (p = 0.001) and slower completion of the FSST (p < 0.001) than healthy cont

Center of Pressure Symmetry in Individuals with Severe Ankle Osteoarthritis

Ankle osteoarthritis (OA) is a debilitating diagnosis that leads to deformity, severe pain, and functional disability. Ankle OA leads to significant quality of life reduction equivalent to end stage kidney disease, congestive heart failure, and end stage hip arthritis. The mechanical cause of this extreme disability in this population is poorly understood, especially in regards to the path of loading across the foot. Alterations in the path of the center of pressure (COP) can be a reflection of gait dysfunction. PURPOSE: Examine the differences in COP pathways during level walking between the healthy and affected limbs in individuals with severe ankle OA. METHODS: Ground reaction forces (GRF) were collected using 4 embedded force plates, during 7 self-selected speed level walking trials along a 10 meter walkway for 175 subjects with primary, unilateral, severe ankle OA. COP pathways were calculated for both the affected (AL) and healthy (HL) limbs. Stance time, mean COP velocity (normalized to stance time), total COP path length (normalized to foot length), and medial-lateral deviation of the COP were examined to assess the symmetry between limbs. Paired t-tests were used to determine statistical differences (alpha =0.05). RESULTS: Average height, weight, and age for the sample was 1.73 ± 0.10 meters, 88.04 ± 16.58 kg, and 61.5 ± 9.5 years old, respectively. Subjects walked with an average velocity of 0.98 ± 0.22m/s. The stance time (AL: 0.66±0.11s; HL: 0.69 ± 0.11s; p<0.001), and total path length (AL: 0.85±0.10% foot length, HL: 0.88±0.08% foot length; p<0.001) were shorter on the affected limb, while the medial-lateral deviation was greater (AL: 44.33 ± 19.52mm; HL: 35.88 ± 13.55mm; p<0.001) on the affected limb. The mean COP velocity was not different between the affected (1.30 ± 0.23mm/s) and healthy (1.30 ± 0.20mm/s) limbs. CONCLUSIONS: Individuals with severe, debilitating ankle OA demonstrate asymmetric COP movement during level walking. The shorter total path length in combination with a shorter stance time on the affected limb indicates that these patients reduce weight bearing time, and potentially push-off from a more proximal portion of their foot. This in combination with the greater medial-lateral deviation on the affected limb could indicate a toe-out posture and midfoot toe-off, both of which could reduce moments around the ankle.

Multinomial Logistic Regression Model for Predicting Driver’s Drowsiness Using Only Behavioral Measures

The aim of this study was to explore the effectiveness of behavioral evaluation measures for predicting drivers' subjective drowsiness. Behavioral measures included neck bending angle, back pressure, foot pressure, COP (center of pressure) movement on sitting surface and tracking error in driving simulator task. Drowsy states were predicted by means of the multinomial logistic regression model where behavioral measures and subjective evaluation of drowsiness corresponded to independent variables and a dependent variable, respectively. First, we compared the effectiveness of two methods (correlation coefficient-based method and odds ratio-based method) for determining the order of entering behavioral measures into the prediction model. It was found that the prediction accuracy did not differ between both methods. Second, the prediction accuracy was compared among the numbers of behavioral measures. The prediction accuracy did not differ among four, five and six behavioral measures and it was concluded that entering at least four behavioral measures into the prediction model is enough to achieve higher prediction accuracy. Third, the prediction accuracy was compared between the strongly drowsy and the weakly drowsy groups. The prediction accuracy differed between the two groups and the proposed method was effective under the condition where drowsiness was induced to a larger extent. Language: en

A study of the immediate effects of glycerine-filled insoles, contoured prefabricated orthoses and flat insoles on single-leg balance, gait patterns and perceived comfort in healthy adults.

BackgroundFootwear interventions are often prescribed to assist with the management of lower limb pain, injury and disease. Commercially available shoe insoles and orthoses are increasingly incorporating novel design features to alleviate foot and lower limb symptoms, but this may be at a cost to optimal functional performance. This study compared the immediate effects of wearing glycerine-filled insoles, contoured prefabricated orthoses, and flat insoles, on balance and gait measures.MethodsThirty healthy adults (17 men, 13 women; mean [SD] age: 24.3 [2.5] years) performed tests of single-leg standing with eyes open (Kistler force platform), star excursion balance test, and level-ground walking (GAITRite® walkway system), under three randomised conditions: wearing glycerine-filled insoles, prefabricated orthoses, and flat (control) insoles, within their own footwear. Centre of pressure movement (anterior-posterior and mediolateral range and standard deviation, total path velocity), star excursion balance test reach distance, and temporospatial gait variables were collected. Perceived comfort of the inserts was scored immediately after use on a 100 mm visual analogue rating scale. After trialling all inserts each participant ranked their level of comfort from least to most.ResultsCentre of pressure measures, star excursion balance test reach distance, or temporospatial gait variables did not differ between the three inserts (all P values >0.088). Significant between-condition differences were reported for comfort ranking (P = 0.031), but not rating scores (P = 0.638). Weak to moderate negative correlations (r values ranged between −0.368 and −0.406) were observed between visual analogue scale comfort rating for the flat insoles and prefabricated orthoses, star excursion balance test and gait measures.ConclusionsSingle-leg standing balance, star excursion balance test performance, and level-ground walking patterns in asymptomatic adults do not appear to differ when wearing glycerine-filled insoles, contoured prefabricated orthoses, or flat insoles. Perceived comfort may be related to the biomechanical or clinical effectiveness of novel footwear interventions, and requires further investigation. Importantly, these findings are specific to a healthy population and further research is needed to determine the long-term effects of glycerine-filled insoles in patients with known balance impairments.

Multinomial Logistic Regression Model for Predicting Driver's Drowsiness Using Behavioral Measures

The aim of this study was to explore the effectiveness of behavioral evaluation measures for predicting drivers’ subjective drowsiness. Behavioral measures included neck vending angle (horizontal and vertical), back pressure, foot pressure, COP (Center of Pressure) movement on sitting surface, and tracking error in driving simulator task. Drowsy states were predicted by means of the multinomial logistic regression model where physiological and behavioral measures and subjective evaluation of drowsiness corresponded to independent variables and a dependent variable, respectively. First, we compared the effectiveness of two methods (correlation coefficient-based method and odds ratio-based method) for determining the order of entering behavioral measures into the prediction model. It was found that the prediction accuracy did not differ between both methods. Second, the prediction accuracy was compared among the numbers of behavioral measures. The prediction accuracy did not differ among four, five, and six behavioral measures, and it was concluded that entering at least four behavioral measures into the prediction model is enough to achieve higher prediction accuracy. Third, the prediction accuracy was compared between the strongly drowsy and the weakly drowsy group. The prediction accuracy differed between the two groups, and the proposed method was effective (the prediction accuracy was significantly higher) especially under the condition where drowsiness was induced to a larger extent.

The dominant foot affects the postural control mechanism: examination by body tracking test

Conclusion: The antero-posterior (AP) body tracking test (BTT) showed that the dominant foot could affect the tilt angle of the sway movement, delineated by primary component analysis. Differences associated with the dominant foot could represent the difference in space perception of each person. Objectives: To examine whether the dominant foot could affect the postural control mechanism using the BTT. Methods: Ninety-seven healthy participants enrolled in the study were classified into right-foot and left-foot dominance groups, and their performances were compared. For the BTT, each participant stood on a stabilometer and caught the movement of a visual target moving vertically (anterior-posterior) or horizontally by the center of pressure movement, displayed on a 14-inch screen monitor at 100 cm in front of the subject. The mean displacement angle of the obtained stabilogram was evaluated by principal component analysis. Results: The AP BTT in the right-foot dominance group showed a clockwise tilt with a mean displacement angle of 3.022 ± 3.761°, whereas the group with left-foot dominance had a modest counter-clockwise tilt with a mean displacement angle of –0.694 ± 4.497°. This difference was found to be significant by the independent t test (p < 0.0001). In the lateral BTT, the mean displacement angles were not significant.

Seat surface inclination may affect postural stability during Boccia ball throwing in children with cerebral palsy.

The aim of the study was to examine how seat surface inclination affects Boccia ball throwing movement and postural stability among children with cerebral palsy (CP). Twelve children with bilateral spastic CP (3 with gross motor function classification system Level I, 5 with Level II, and 4 with Level III) participated in this study. All participants underwent pediatric reach tests and ball throwing performance analyses while seated on 15° anterior- or posterior-inclined, and horizontal surfaces. An electromagnetic motion analysis system was synchronized with a force plate to assess throwing motion and postural stability. The results of the pediatric reach test (p = 0.026), the amplitude of elbow movement (p = 0.036), peak vertical ground reaction force (PVGRF) (p < 0.001), and movement range of the center of pressure (COP) (p < 0.020) were significantly affected by seat inclination during throwing. Post hoc comparisons showed that anterior inclination allowed greater amplitude of elbow movement and PVGRF, and less COP movement range compared with the other inclines. Posterior inclination yielded less reaching distance and PVGRF, and greater COP movement range compared with the other inclines. The anterior-inclined seat yielded superior postural stability for throwing Boccia balls among children with bilateral spastic CP, whereas the posterior-inclined seat caused difficulty.

Low Cognitive Status Is Associated with a Lower Ability to Maintain Standing Balance in Elderly Outpatients

Background: Evidence is emerging that cognitive performance is involved in maintaining balance and thereby involved in falls in the elderly. Objective: To investigate the association of cognitive status with measures of standing balance in elderly outpatients. Methods: In a cross-sectional study, 197 community-dwelling elderly [mean age (SD) 81.9 (7.1) years] referred to a geriatric outpatient clinic were included and subsequently dichotomized into a group with low and normal cognitive status based on cut-off values of the Mini-Mental State Examination, Montreal Cognitive Assessment and Visual Association Test. The ability to maintain standing balance as well as the center of pressure (CoP) movement were assessed during 10 s of side-by-side, semi-tandem and tandem stance with eyes open and eyes closed. Logistic and linear regression were used to examine the association between cognitive status and measures of standing balance adjusted for age, gender and highest completed education. Results: Low cognitive status in elderly outpatients was associated with a lower ability to maintain 10 s of balance in side-by-side stance with eyes closed [OR (95% CI): 3.57 (1.60; 7.97)] and in semi-tandem stance with eyes open and eyes closed [OR (95% CI): 3.93 (1.71; 9.00) and OR (95% CI): 2.32 (1.11; 4.82), respectively]. Cognitive status was not associated with CoP movement. Conclusion: Low cognitive status associates with a lower ability to maintain standing balance in more demanding standing conditions in elderly outpatients. This may have implications for routine geriatric screening strategies and interpretation of results of either standing balance or cognitive tests.

A new measure of the CoP trajectory in postural sway: Dynamics of heading change

The maintenance of upright stance requires the simultaneous control of posture in both the anterior–posterior (AP) and medial–lateral (ML) dimensions. Postural sway is typically measured by quantifying the movement of the center of pressure (CoP) in the AP and ML dimensions independently. Metrics such as path length and 95% ellipse area have been developed to take into account movement in both the AP and ML directions, but these metrics only quantify the magnitude of the CoP movement. The movement of the CoP is technically a vector quantity with both magnitude and direction characteristics. The direction of displacement, or heading, of the CoP may provide further insight into the control of posture. Accordingly, we present a novel variable that describes the rate of change in direction of CoP displacement in two dimensions, the heading change (Δϕ), which is derived from the CoP heading (ϕ). We then compared the standard deviation (SD) and the dynamic structure characterized by sample entropy (SampEn) of the heading change time series to previously examined metrics presented in the literature (SD and SampEn of the AP and ML time series, path length, SD and SampEn of the CoP resultant magnitude time series) during a 60s single-leg stance performed by healthy participants and patients with a ruptured anterior cruciate ligament (ACL) prior to surgical intervention. Patients with an ACL rupture exhibited a different dynamic structure in Δϕ compared to healthy controls, t(14)=2.44, p=0.029, whereas none of the other metrics differed between groups (all p>0.05). The novelty and utility of Δϕ is that it characterizes directional changes of the CoP, whereas previously documented postural control analyses describe only changes in magnitude.

Postural stability in subjects with whiplash injury symptoms: results of a pilot study

Conclusions: Posturographic tests can be used to assess and confirm the body’s imbalance in subjects with whiplash injury. Further studies with larger cohorts are necessary to confirm this pilot study. Objectives: To verify through a posturographic exam the qualitative and quantitative alterations of postural stability in subjects with previous cervical trauma in comparison with healthy subjects. Methods: A total of 42 subjects were analysed for the study; 22 as the control group (NM) and 20 (WM) with a positive anamnesis of whiplash injury from 3 to 12 month from diagnosis through a force platform. Centre of pressure (CoP) movements of the two groups with their eyes open and closed were recorded. Results: During the closed eye test, the subjects with cervical injuries displayed a significant increase in the anterior-posterior oscillation velocity (p < 0.05) compared with the control group, with a significant reduction (p < 0.01) of the ratio between the shifting length (SL) of CoP on the polygon support and the total envelope area (EA, mm2) of CoP movements in the polygon support (SL/EA-ratio, mm–1).