静的立位姿勢における足圧中心動揺変数相互の関係の検討―領域別及び性差の観点から―

In previous studies, many evaluation parameters for the center of foot pressure (CFP) in a static standing posture have been proposed, but their reliability and inter-relationships have not been sufficiently examined.The purposes of this study were to examine trial-to-trial reliability and the inter-relationships of various evaluation parameters and to propose useful ones. Thirty healthy young adults were selected as subjects. The measurement of CFP for 1 minute was carried out 10 times with 1 minute rest for each subject. The measurement device was an Anima's stabilometer G5500. The data was recorded every 20 msec. Seventy-six evaluation parameters, excepting composite parameters from 114 parameters proposed in previous studies, were selected from the following domains: distance, center of pres-sure, distribution of amplitude, area, velocity, power spectrum, and vector for body sway. The intraclass correlation coefficients (ICC) for 10 trials were 0.7 or over for all parameters excepting for the X-axis and the Y-axis distribution for body sway, and skewness and kurtosis for body sway speed, but a significant difference between the first trial and the other trials was found in many parameters. Therefore, the ICC was recal-culated by excluding the first trial. As a result, no significant difference was found other than that of the distance of the root of the mean square and the area of the root of the mean square. The ICC was 0.7 or over, excepting for the following parameters: the X-axis and the Y-axis distribution for body sway and skewness and kurtosis for body sway speed, the cross correlations for body sway and body sway speed, the C ratio of the power spectrum area on the X-axis, the A ratio of the power spectrum area on the Y-axis and the root of the mean square-axis. Inter-correlation coefficients between parameters in each domain of distance, center of pressure, distribution of amplitude, area, velocity, power spectrum, and vector for body sway were mostly high values of 0.9 or over. Thus, it was considered that there is a close relationship between theoretically similar parameters and any of them could be selected as useful parameters.Based on the above-stated examination, 60 evaluation parameters shown in Table 5 were finally selected.

To examine the influence of alcohol intake on various parameters evaluating the change in body center of foot pressure during a static upright posture, 11 healthy young males and females gave measures of blood pressure, heart rate, whole body reaction time, standing on one leg with eyes closed, and body stability for 60 sec. in the Romberg posture (open eyes, closed feet) before and after the alcohol intake. The measurement was made with an Anima's stabilometer G5500. Data sampling frequency was 20 Hz. The subjects drank alcohol (Japanese sake 540 ml) within 10 min. After 10, 20, and 30 min. of alcohol intake, the same measurements were carried out. 24 parameters with higher trial-to-trial reliability were selected from the following 7 domains: distance, mean center of foot pressure, distribution of amplitude, area, velocity, frequency (power spectrum), and direction (vector) of body-sway and velocity. Parameters for distance, velocity, and area of body-sway significantly changed after alcohol intake, but the mean center of foot pressure and frequency of body-sway were unchanged. It was inferred that the mean center of foot pressure and frequency for body-sway did not change even if a nervous function decreased by the alcohol intake, and an upright posture was maintained by increasing the distance, area, and velocity of body-sway. Further, body-sway tends to increase in the medial/lateral direction as compared with the anterior/posterior direction.

Electromyographic (EMG) patterns of leg muscles associated with rapid body sway were studied in relation to displacement of the center of foot pressure (CFP). Standing subjects were instructed to shift the CFP by swaying their bodies, pivoting at the ankle as rapidly and accurately as possible after an auditory signal. CFP position was designated as N when the subject maintained a relaxed bending posture and as F when a maximally forward-leaning posture was maintained. A serial, stereotyped triphasic EMG pattern was observed in the rapid shift of CFP from N to F: cessation of EMG activity in the gastrocnemius (GC) muscle was followed by a burst in the tibialis anterior (TA) muscle (acceleration phase), and then resumed discharge occurred in the GC muscle with cessation of activity in the TA muscle (deceleration and stop). When the subject shifted the CFP from N to F to different degrees, the duration and amount of EMG activity in the TA muscle during acceleration and the GC muscle in deceleration were proportionate to the amount of CFP displacement associated with forward body sway. To determine the functional roles of sensory inputs from the foot on the triphasic EMG pattern, body sway was studied under the condition of sensory block in the feet induced by ischemia from tourniquets placed bilaterally just above the ankle joints. The triphasic EMG pattern persisted during ischemia. The time of GC cessation and the onset of TA burst at acceleration remained unchanged, but the times of TA cessation and resumption of GC discharge at deceleration were altered during ischemia. Moreover, subjects were unable to stop at F and eventually fell. These results indicate that both amount and duration of EMG activity associated with rapid body sway are functions of the amount of CFP displacement. Somatic sensation from the feet is important for control of burst and cessation timing and duration in leg muscle activity.

Seiza is one of the most commonly used sitting postures in various enrichment lessons of Japanese origin. It is reported that Seiza with large knee flexion produces harmful effects on the cartilage of knee joints and hemodynamics of the lower legs. This study aimed at examining the influence of Seiza on tissue oxygenation kinetics of the lower limbs, plantar somatic and cutaneous sensation, and the center of foot pressure (COP) sway using 10 young adults. COP sway was measured for 1 min just after sitting on a chair for 10 min (pre-test), after 30-min Seiza (post-test 1), and 5 min after Seiza (post-test 2). To evaluate the COP sway, we used 4 body sway factors; unit time sway factor (F1), front-back sway factor (F2), left-right sway factor (F3) and high frequency band power spectrum factor (F4). Physiological parameters (i.e., tissue oxygenation kinetics in the lower legs and sensation on the sole) were measured during 30-min Seiza (continuously on tissue oxygenation, and at 1 min intervals on sensation), and for 1 min just before each COP test (pre-test, post-test 1 and 2). Oxygenated hemoglobin/myoglobin (Hb/Mb) concentration decreased markedly and deoxygenated Hb/Mb concentration increased markedly, resulting in reaching a plateau state at around 7 min. Tissue Hb/Mb index changed little during Seiza. Proprioceptive perception thresholds increased rapidly about 17 min after Starting Seiza. Means of 3 COP sway factors of F1, F2 and F4 were significantly higher in post-test 1 than in pre-test and post-test 2. In conclusion, a marked decrease in tissue oxygen concentration of the lower legs within 4-5 min, and an increase of proprioceptive perception thresholds in the sole at about 17 min are induced by Seiza. Although wiggle and quick body sway in the antero-posterior axis increases markedly in an upright posture just after maintaining Seiza for 30 min, sway recovers after sitting on a chair for 5 min.

This study aimed to examine the effects of open/ closed eyes and age difference on Center of Foot Pressure (COP) sway during stepping. The subjects were 87 healthy males aged 10 - 80 years. COP was measured 20 times when subjects stepped on two force plates (left and right) at a rate of 60 steps/min. The evaluation parameters selected were: total trace length, velocity, circumference, rectangular area，left-right width, and front-back width. The former four of these parameters were found to be significantly lower with eyes open than eyes closed in 80-year-old subjects, while the last parameter was significantly lower with eyes open in 10-year-old subjects. In 70- and 80-year-old subjects with eyes open, circumference was greater than that in 10- and 40 - 60-year-old subjects; their rectangular area was greater than that in 50- and 60-year-old subjects; and, their front-back width was greater than that in 10- and 30 - 60-year-old subjects. With eyes closed, circumference, rectangular area, left-right width, and front-back width in 80-year- old subjects, were greater than those in 10 - 70- year-old subjects. The front-back width during stepping with eyes closed was greater in 70- and 80-year-old subjects than in 30 - 50-year-old subjects. The Romberg quotient for all COP sway parameters revealed no significant age-related differences. From our findings, a difference in body sway was observed in 80-year-old subjects (with eyes open/closed) when compared with the other age groups. In addition, the extent of sway varied little among 80 year-old- subjects have greater body sway during stepping, particularly with eyes closed.

Alterations of body sway caused by isometric contractions of the jaw muscles have been reported previously. The objective of this study was to test if motor tasks of the masticatory system with different control demands affect body posture differently during quiet stance. Position and sway displacements of the center of foot pressure (COP) were measured for 20 healthy subjects who either kept the mandible at rest or performed unilateral and bilateral maximum voluntary teeth clenching, feedback-controlled biting tasks at submaximum bite forces, or unilateral chewing. Two weeks later the measurements were repeated. Compared with quiet stance, the COP results revealed significant changes during the feedback-controlled biting tasks. Robust sway reduction and anterior displacement of the COP were observed under these conditions. Body oscillations were not significantly affected by maximum bites or by unilateral chewing. For most of the variables investigated there were no significant differences between unilateral and bilateral biting. Robust sway reduction during feedback-controlled biting tasks in healthy subjects involved a stiffening phenomenon that was attributed to the common physiological repertoire of posture control, and might optimize the stability of posture under these conditions.

This study was done to examine age-stage (preschool children, young adults, and elderly people) differences in the center-of-pressure sway using body-sway factors (unit-time sway, front-back sway, left-right sway, and high frequency-band power), power-spectrum distribution, and relative accumulation of power frequency (25%, 50%, and 75% RAPF) of the center-of-pressure spectrum. The center-of-pressure movement for 1 min. was measured twice using Anima's stabilometer. Data-sampling frequency was set at 20 Hz. Significant age-stage differences were found for 3 factors except for left-right sway, which was larger for preschool children and elderly than for young adults. The power spectrum of body sway in any age-stage was noted mainly in low frequency bands. A marked age-stage difference was found at 75% RAPF. Body-sway characteristics in each age-stage differ, and differences of postural-sway frequency are marked in the low frequency bands.

Time course of stabilometric changes after a strenuous treadmill exercise

Curved walking in hemiparetic patients

The relationship between the movement of the centre of foot pressure in the anterio-posterior plane and the rotation which occurs in the same plane at the level of the ankles, hips and shoulders during postural sway was examined in a group of normal human subjects. Expressed as three frequency-dependent functions this relationship consists of both relative magnitude and phase components. The magnitude component indicates that the pressure centre was most sensitive to ankle rotation, less to hip and least sensitive to rotation at the level of the shoulders. The sensitivity of the pressure centre was also a function of the frequency of the rotations and this is evidenced by the presence of several resonant peaks in the relationship. It is suggested that these could be due to body inertia and transmission delays. The resonant peaks became more prominent when the subjects stood with eyes closed. The growth of resonant peaks is taken as a sign of reduced postural stability and on this basis it is argued that a distinction should probably be made between the concepts of the stability and the steadiness of stance.

The present study examined the differences between male and female gymnasts in bipedal standing position, back standing scale, and stork standing scale testing. 29 young gymnasts (13 boys, 16 girls; ages 12 to 15 years) participated. A portable posturographic digital platform was used to record foot pressure (Foot Checker, Comex SA). Barefoot sole area (cm2), maximal pressure (kPa), center of foot pressure (CoP), sway area (mm2), and CoP linear distance displacement (mm) were analyzed in an integrated software module (Foot Checker, Version 4.0). The intra-class correlation coefficient and the coefficient of variation supported the reliability of the measurements. Results indicated no differences between boys and girls on height, weight, and Body Mass Index. Differences indicated better performance by girls compared to boys in back standing and stork standing.

In 1983, the board of the Japan Society for Equilibrium Research presented a standard of stabilometry, but some problems remain.In order to determine the test conditions, we performed the following examination with a standard stabilometer.1 . For visual target testing, the distance from the subject to the target and the illumination of the peripheral visual field were studied.2. For the standing posture, body sway in the military standing posture was compared with that in natural standing.3. For foot position, body sway while standing with both feet together was compared with that feet in the fan-shaped position and with feet apart but parallel.4. For recording time, body sway while standing for 30 seconds was compared with that while standing for 60 seconds.5. To elimilinate transitional sway after standing erect with eyes closed, the time when the recording should start was studied.The parameters for stabilometry are as follows ; unit locus lengh, forward-backward and right-left diameters, area, rejection ellipse, center of sway, standard deviation, skewness and kurtosis of amplitude probability density distribution, velocity, vector of velocity, power spectrum.1. When the visual target was placed one meter from the subject and the peripheral field of vision was lighted, the mean and standard deviation of all parameters in stabilometry were the smallest.2. Standard deviations of the unit locus length, area and velocity during military posture standing were lower than during natural standing. However, maintenance of military standing for 60 seconds was difficult. Therefore, stabilometry with natural standing was considered more suitable for clinical examinations.3. Body sway while standing with feet 10 cm apart was less than when standing with the feet close together or in the fan-shaped position. However, standing with the feet close together was suitable for detecting slight equilibrium disturbances.4. Body sway observation for 60 seconds clarified the pattern of the body sway more definitely than did observation for 30 seconds.5.Irregular sway was recorded after the subject stood erect with eyes closed for 10 seconds. To eliminate transitional sway, the recording should be started when the body movements of the standing subject are stabilized.

ACL Research Retreat V

The cognitive trait of hypnotizability, associated with the proneness to accept suggestions, exhibits several physiological correlates including the modulation of sensorimotor integration and, in particular, of postural control. In this respect, we have shown that, at eyes closure, healthy subjects with high hypnotizability scores (highs) having their feet 2 cm apart show larger and faster body sway with respect to low hypnotizable individuals (lows). The aim of the present study was to investigate whether hypnotizability modulates body sway during slightly more demanding and very difficult postural conditions such as feet together bipedal posture and one legged stance, respectively. The Center of Pressure (CoP) Area, mean Velocity, the CoP mean position (Xmean, Ymean) and its variability (SDx, SDy) in the frontal and sagittal planes were acquired in 18 highs (9 females) and 18 lows (9 females). Results showed that the previously observed lows' smaller and slower body sway was not present any longer. Nonetheless, hypnotizability interacted with gender in the modulation of the variability of the CoP movement in the frontal plane during both the bipedal feet together posture and one legged stance, as significant gender differences were observed only among lows. In conclusion, results confirm a role of hypnotizability in sensorimotor integration and support the relevance of hypnotic assessment in clinical settings, as hypnotizability may be responsible for part of the postural variability.

The upright standing posture of human beings is unstable because of the inverted pendulum characteristics of the body. The posture control function is explained in the physiology by the stretch reflexes. The functional properties of the posture control are reflected to the area of body away during standing. Such integrated information as area of body sway and length of locus of body sway is applied to the diagnosis of sensory disabilities affecting posture control and the physical education study, etc. However, there have been few reports on the differential information of body sway. The aim of this study is to propose an extraction method of differential information from the time series of the center of foot pressure (CFP) at standing using an autoregressive model. The differential information proposed here is the velocity, the acceleration, and the wave number of the time series of CFP. It describes the relation between the differential information and integrated information of body sway. The differential information is effective in evaluating the postural reflex during an upright standing task.