Deviation Of Center Of Pressure Research Articles

The influence of high- and low-heeled shoes on balance in young women.

To evaluate the influence of two different heel heights on static balance and on limits of stability during functional reach test, with both the eyes open and eyes closed, in young women (age 22-27) who did not wear heeled shoes habitually. Thirtyone young women (age 22-27) performed balance tests on a stabilometric platform without footwear and in shoes with 4 cm and 10 cm heels. The center of pressure (COP) deviations range and velocity in anteroposterior (AP) and mediolateral (ML) directions were assessed. The limits of stability were measured when the subject leaned the body in sagittal plane. The ranges of COP deviations in AP and ML directions were already significantly higher in 4 cm heels in comparison to the barefoot condition. COP deviation velocity significantly raised with increasing heel height as well as when the eyes were closed. A more pronounced increase of COP deviation velocity than COP deviation range when measurement conditions become more difficult may indicate that young women anticipate postural corrections by stimulation of ankle proprioception when heeled shoes are worn. High-heeled shoes may lead to alterations in velocity feedback balance mechanism, which may increase the risk of musculoskeletal injuries. Observed in our study adverse effect of heeled footwear on balance may predispose women to falls and injuries. Permanent use of stiletto high heels should be avoided by women.

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.

Analysis of medial deviation of center of pressure after initial heel contact in forefoot varus.

After initial heel contact, the rearfoot everts and causes medial deviation of the center of pressure (CoP). Although rearfoot angle in single-limb stance has been associated with forefoot varus (FV)≥8°, medial CoP deviation has not. After 12 participants with FV<8° (neutral group) and 11 participants with FV≥8° (FV group) stepped one heel initially onto an array of pressure sensors parallel to its Y coordinate axis, when the CoP of array deviated most medially, the X coordinate of the CoP of each row was calculated to find the most medial CoP of the row. Starting since the row with the most medial CoP just began to have the same sensors with pressures >0kPa as when it had the most medial CoP, the medial deviations of the CoP of the array, the most medial CoP of the row, and its relative position in the row (CoP%), were compared between neutral and FV groups. The medial deviations of the most medial CoP of the row (1.1±0.6 vs. 1.6±0.3mm, p=0.049) and CoP% (2.9±1.4 vs. 4.2±1.1%, p=0.023) were significantly different between neutral and FV groups, whereas that of the CoP of the array (1.1±0.6 vs. 1.4±0.6mm, p=0.36) was not. The most medial CoP of the row and CoP% detected increased medial CoP deviation in FV≥8°, and may be applied to other clinical conditions where rearfoot angle and CoP of the array after initial heel contact cannot detect significant differences.

Effects of heel base size, walking speed, and slope angle on center of pressure trajectory and plantar pressure when wearing high-heeled shoes

High-heeled shoes are associated with instability and a high risk of fall, fracture, and ankle sprain. This study investigated the effects of heel base size (HBS) on walking stability under different walking speeds and slope angles. The trajectory of the center of pressure (COP), maximal peak pressure, pressure time integral, contact area, and perceived stability were analyzed. The results revealed that a small HBS increased the COP deviations, shifting the COP more medially at the beginning of the gait cycle. The slope angle mainly affected the COP in the anteroposterior direction. An increased slope angle shifted the COP posterior and caused greater pressure and a larger contact area in the midfoot and rearfoot regions, which can provide more support. Subjective measures on perceived stability were consistent with objective measures. The results suggested that high-heeled shoes with a small HBS did not provide stable plantar support, particularly on a small slope angle. The changes in the COP and pressure pattern caused by a small HBS might increase joint torque and muscle activity and induce lower limb problems.

Toilet Grab-Bar Preference and Center of Pressure Deviation During Toilet Transfers in Healthy Seniors, Seniors With Hip Replacements, and Seniors Having Suffered a Stroke

Multiple toilet grab-bar configurations are required by people with a diverse spectrum of disability. The study purpose was to determine toilet grab-bar preference of healthy seniors, seniors with a hip replacement, and seniors post-stroke, and to determine the effect of each configuration on centre of pressure (COP) displacement during toilet transfers. METHODS: 14 healthy seniors, 7 ambulatory seniors with a hip replacement, and 8 ambulatory seniors post-stroke participated in the study. Toilet transfers were performed with no bars (NB), commode (C), two vertical bars (2VB), one vertical bar (1VB), a horizontal bar (H), two swing-away bars (S) and a diagonal bar (D). COP was measured using pressure sensitive floor mats. Participants rated the safety, ease of use, helpfulness, comfort and preference for instalment. RESULTS: 2VB was most preferred and had the smallest COP deviation. Least preferred was H and NB. C caused largest COP displacement but had favourable ratings. DISCUSSION: The preference and safety of the 2VB should be considered in the design of accessible toilets and in accessibility construction guidelines. However these results need to be verified in non-ambulatory populations. C is frequently prescribed, but generates large COP deviation, suggesting it may present an increased risk of falls.

Optical Push by Geographical Slant Affects Postural Sway

This study shows that perceived geographical slant affects postural stability. In 2 experimental conditions participants stood on a force platform that measured center of pressure (COP) during quiet stance while looking at a rigid, flat ramp surface of varying geographical slants. Using an otherwise identical procedure, participants in the second condition also provided verbal estimates of the steepness of the surface in degrees. Several measures of postural stability offered converging evidence that COP sway gradually increased as geographical slant decreased to 0 (horizontal ground). Specifically, COP was sensitive to changes in surface slant. Both the range and the standard deviation of COP showed the same trend of increased variability with decreasing geographical slant angles in both conditions. The area of the ellipse covering COP sway (based on a principal components analysis) showed the same tendency: ellipse area got larger for smaller, more horizontal slants. Nonlinear fractal dynamics of COP sway, as measured by the Hurst exponent of COP, pointed in the same direction: more fractal patterns, known to be correlated with increased muscle activity and decline in postural stability, were measured for shallower surface slants. There were no effects of verbal estimates on any of the measures, suggesting that explicit awareness of slant does not bias postural stability above and beyond the effects of visual environment.

Compensatory postural sway while seated posture during tasks in children with autism spectrum disorder.

Postural stability while seated was investigated in 16 children with autism spectrum disorder (ASD) and 16 typically developed (TD) children, aged 7-8 years. The lateral and antero-posterior (A-P) deviations of the centre of pressure (COP) were serially measured during sequential, upper limb, desk-top tasks, including nine subtests. The average COP deviation was larger, especially in the lateral direction, in the group of children with ASD compared with TD children. However, the larger COP deviation in the children with ASD was not generalized across tasks. Analyses of subtests revealed that deviations were different on three and four (of eight) subtests in the lateral and A-P directions, respectively. The time needed to complete each subtest was not correlated with the lateral COP deviation but with A-P deviation during the subtest in the children with ASD. Preserved task performance with marked body sway in the children with ASD suggested that the body sway was not a functionally abnormal movement that disturbed performance but could be a compensatory movement to actually facilitate performance. A new approach with occupational therapy to support such compensatory movement of ASD children could be considered in their school life. Further studies, including those in the classroom, to clarify the relationship between daily task performance and body instability are necessary.

El procesado del desplazamiento del centro de presiones para el estudio de la relación complejidad/rendimiento observada en el control postural en bipedestación

ObjectiveThe aim of this study is to analyze the relationship between the complexity and postural balance in a standing balance task. In this way, this study assesses the effect of the sample frequency, the stationarity of center of pressure (COP) and the used of different analysis. MethodTwenty-one volunteers were asked to stand still for 30 s on a stable surface Displacement of COP was measured. The performance was assessed through the standard deviation (SD) of COP. Complexity of COP was measured through Sample Entropy (SampEn) and Detrended Fluctuation Analysis (DFA). All variables were analyzed on three different frequencies (20,100 and 1000Hz) and on two signal treatment (the original and detrended signal). ResultsThe sample frequency influences the values of SampEn and DFA. However, these values keep the trend shown between experimental conditions. SD values are negatively related with SampEn of COP data in both axes. Nevertheless, the relationship between SD and DFA varies by axis; this relationship is negative in the AP axis and positive in the ML axis. ConclusionThe sample frequency has a significant influence in the results, but frequencies close to the dynamics of COP enhance the differences. On the other hand, we suggest to detrend the signal to improve the analysis of dynamics of COP. The results support the direct relationship between performance and complexity of COP.

El método Kinesio taping mejora inmediatamente el equilibrio monopodal en deportistas mayores sanos

ObjectiveTo evaluate the immediate effects of the Kinesio taping (KT) method on standing balance in a group of healthy senior tennis players. MethodsA total of 16 subjects participated in this cross-over study. The sample was randomly divided into two groups and the sequence of the taping technique, either KT or a placebo technique, to be used was determined. Center-of-pressure (COP) variables were measured, performing balance tests with unipedal stance on a force platform, with eyes opened and with eyes closed. Measures were taken before the taping, immediately after its application and 24hours after taping. ResultsThe KT method significantly improved the COP total length path in the eyes opened test immediately after the KT application. In the eyes closed test, that outcome significantly improved with KT immediately after the intervention and 24hours later, exceeding the placebo technique. There was a significant improvement of the anteroposterior COP deviation in the eyes closed test, immediately after the application of the KT. This technique outperformed the placebo in the mediolateral deviation of the COP with the eyes closed over the placebo at 24hours. ConclusionThe KT method immediately improved the standing balance of the subjects, this being reflected in the length of the COP in the anteroposterior deviation with eyes closed, an improvement that tends to be maintained at 24hours with the technique still applied.

Broad Stance Conditions Change Postural Control and Postural Sway

ABSTRACT Intuitively, a broad stance (i.e., standing with the feet farther apart than usual) should significantly improve postural stability. However, this intuition was not confirmed in quiet stance. Hence, a motion analysis system (markers attached to the trunk and head) and a force platform were used to investigate 13 healthy, young adults who performed 8 trials in standard and broad stances. In broad stance, the medialateral center of pressure (COP) sway mean power frequency was expected to be greater, whereas the variability (standard deviation) of COP, head, and trunk sway and the mean velocity of head and trunk sway was expected to be significantly lower. Accordingly, adoption of a broad stance significantly increased the medialateral mean power frequency of COP sway; decreased the standard deviation of medialateral COP, trunk, and head sway; and decreased the medialateral mean velocity of head sway. A broad stance was also associated with lower variability for head and COP sways in the anteroposterior axis. Unexpectedly, an effect of trial repetition was found for the variability of medialateral trunk sway. This was probably due to the break halfway through the study. In practical terms, broad stance conditions can improve postural control in the medialateral and anteroposterior axes.

Cluster Analysis of Center-of-Pressure Measures

− Postural stability analysis is useful in a variety of applications, such as assessing the risk of falls for older adults or investigating neuromuscular disorders. Variations in the center-of-pressure (COP) are often used to assess postural stability. The COP is a point where the vertical reaction forces of the ground act. It represents the weighted average of all pressures over the body in contact with the ground. Static posturography, which analyses COP variations during a fixed standing posture, is a non-invasive assessment technique, used to quantify postural stability. The objective of this study is to investigate the performance of six conventional COP measures used to characterize postural stability. Six conventional measures are investigated: i) average radial displacement, ii) average velocity, iii) area of the 95% confidence ellipse, iv) standard deviation of COP in the x-direction (medio-lateral), v) standard deviation of COP in the y-direction (antero-posterior), and vi) standard deviation of radial displacement. These COP measures are compared during four different stability conditions: i) feet together, eyes open, ii) feet together, eyes closed, iii) single leg, eyes open, and iv) single leg, eyes closed. Performance is quantified by cluster analysis using the silhouette coefficient, which provides a measure of how well clustered the four stability conditions are for a given stability measure. A good stability measure should have high repeatability for a given stability condition (low intra-cluster distances) and be able to discern between different stability conditions (high inter-cluster distances). Results from eight subjects suggest that out of the six COP measures examined, average velocity is the best measure to assess postural stability.

How trunk turns affect locomotion when you are not looking where you go

How well do we maintain heading direction during walking while we look at objects beside our path by rotating our eyes, head, or trunk? Common experience indicates that it may be fairly hazardous not to look where you are going. In the present study, 12 young adults walked on a treadmill while they followed a moving dot along a horizontal line with their gaze by rotating primarily either their eyes, head, or trunk for amplitudes of up to 25°. During walking the movement of the center of pressure (COP) was monitored using force transducers under a treadmill. Under normal light conditions, the participants showed little lateral deviation of the COP from the heading direction when they performed the eye or head movement task during walking, even when optic flow information was limited. In contrast, trunk rotations led to a doubling of the COP deviation in the mediolateral direction. Some of this deviation was attributed to foot rotation. Participants tended to point their feet in the gaze direction when making trunk turns. The tendency of the feet to be aligned with the trunk is likely to be due to a preference to have feet and body in the same orientation. Such alignment is weaker for the feet with respect to head position and it is absent with respect to eye position. It is argued that feet and trunk orientation are normally tightly coupled during gait and that it requires special abilities to move both segments independently when walking.

Pressure mapping as a complement in clinical sitting analysis in children during activity

The purpose of this study was to investigate whether pressure mapping can be used as a complement in sitting analysis. The purpose was also to study test–retest reliability and to obtain reference values in healthy children. The children performed a structured activity sitting on the pressure mat. The variables studied in children 4–15 years of age were the mean pressure distribution of one half of the body in relation to the whole sitting surface and the transfer of the centre of pressure (COP) in target reaching in relation to the calculated mean COP when sitting still. The standard deviation for the mean COP was calculated and test–retest for reliability was performed. The results showed significant differences between the youngest children and children 8–15 years of age concerning the transfer of COP sideways and in standard deviation of mean COP sideways. The results for weight distribution, COP transfer sideways and deviation from mean COP sideways were repeatable and consistent with studies of post...

Application of Center-of-Pressure Data to Indicate Rearfoot Inversion-Eversion in Shod Running

Although pressure plates are used to help in the selection of appropriate footwear for runners, evidence relating aspects of pressure data to movement is lacking. A study was conducted to investigate whether center-of-pressure (COP) data obtained for shod running could be used to indicate the amount of rearfoot eversion. It was hypothesized that subjects exhibiting high rearfoot eversion during the initial ground contact phase of running would also show a large lateral-to-medial deviation in the COP. Pressure plate and rearfoot movement data were collected for 33 subjects. The COP was characterized using the lateral-to-medial deviation of the COP during the eversion phase of ground contact. Correlation coefficients were determined for COP deviation versus rearfoot range of motion and versus peak rearfoot eversion (P < .05). In addition, subjects were grouped as high, moderate, or low pronators, and analysis of variance was used to test whether there were significant differences in COP deviation for these three groups (P < .05). The COP deviation was found to have a low correlation with rearfoot range of motion (R = 0.46; P < .05) and with peak rearfoot eversion (R = .54; P < .05). High pronators had significantly higher COP deviation than the medium- and low-pronation groups (P < .05). These findings support the use of COP deviation to detect high pronation. However, caution is advised in using the COP to indicate absolute rearfoot eversion.

Deficits in time-to-boundary measures of postural control with chronic ankle instability

Our purpose was to examine postural control in single leg stance in subjects with and without unilateral chronic ankle instability (CAI) using traditional center of pressure (COP)-based and time-to-boundary (TTB) measures. Fifteen physically active females with self-reported unilateral chronic ankle instability (CAI) and nine healthy female controls performed three 10-s trials of eyes open single limb quiet standing on a force plate on both their legs. The traditional measures were mean COP velocity, standard deviation of COP, range of COP, and percent of available range utilized. The TTB measures were absolute minimum TTB, mean of the minimum TTB samples, and standard deviation of the minimum TTB samples. All measures were calculated in both the mediolateral (ML) and anteroposterior (AP) directions. A 2x2 group (CAI, control) by side (involved, uninvolved) design was utilized. The CAI group had significantly lower scores for five of the six TTB measures compared to the control group, however only one (AP COP velocity) of the eight traditional measures was different between groups. The TTB measures appear to detect postural control deficits related to CAI that traditional measures do not.

Phobic postural vertigo

Patients with phobic postural vertigo (PPV) often report a particularly increased unsteadiness when looking at moving visual scenes. Therefore, the differential effects of large-field visual motion stimulation in roll plane on body sway during upright stance were analyzed in 23 patients with PPV, who had been selected for the integrity of their vestibular and balance systems, and in 17 healthy subjects. Visual motion stimulation induced a sensation of apparent body motion (roll vection) in all patients and normal subjects. Normal subjects showed an increased lateral sway path with a lateral shift of the center of pressure (COP) in stimulus direction (mean 1.67 cm, SD 1.63). The patients also exhibited an increase in sway path during visual motion stimulation; however, their body sway differed from that of normals in that there was no lateral displacement of COP (mean 0.19 cm, SD 0.73). The lateral displacement of COP and the increase in RMS of body sway during visual motion stimulation were significantly greater in normals than in the patients ( p<0.05). The patients' increased body sway without COP deviation does not imply an increased risk of falling. Two explanations are conceivable for this increased body sway without body deviation in patients with PPV: (a) the patients rely more on proprioceptive and vestibular rather than on visual cues to regulate upright stance; or (b) they depend on visual, vestibular, and proprioceptive information, but the threshold at which they initiate a compensatory body sway opposite in direction to a perceived body deviation is lower than in normal subjects. The data support the second explanation.

The effects of foot orthoses on the ground reaction forces during walking. Part 1

The efficacy of functional foot orthoses can be measured in a variety of ways. This particular study looked at the effects foot orthoses had on the vertical ground reaction forces (Fz), the centre of pressure deviation (medial/lateral) and the angle of the sagittal plane ground reaction force vector (GRF) at the time of (peak 1) and (peak 2) on the force/time graph. Ten patients (fivefemale and five male) who fulfilled predetermined criteria were selected for the study. Mean age for the males was 47 (range 29–65) and 35 (range 20–54) for females. All subjects underwent a biomechanical assessment and had functional foot orthoses prescribed then fitted a few weeks later. The devices were made from a variety of materials such as polypropylene, polydor and carbon fibre. Analysis took place between three and six weeks after fitting of the devices with subjects performing five trials over both force plates with and without orthoses. The walkway was covered with paper to hide the position of the plates and ink markers were placed on the shoes at three points to identify where the foot was on the plate for every trial. Subjects wore their own shoes for each trial. Results showed on average a 3%–5% increase in the vertical (Fz) component of force at initial peak (peak 1) when wearing the orthoses. This was much less, −0.15%–0.8% at the second peak (peak 2). Alterations to the sagittal plane ground reaction force vector angle (GRF) were small (<2.78 degrees) and warrant further research as no papers relating to this parameter of measurement with foot orthoses could be found. The centre of pressure (cop) deviation varied up to approximately a centimetre at both peaks when wearing the orthoses. The author feels that the findings have implications for orthoses design in certain patient categories.