Effect of shoes with rounded soft soles in the anterior-posterior direction on the center of pressure during static standing.

Shoes with curved rocker bottom soles may induce an unstable standing posture. This study was aimed to mainly examine the effect of such shoes on the center of pressure (COP) during static standing. Ten healthy young male adults had their COP measured during static standing with four types of shoe conditions (Stretch Walker(®): SW (shoes with curved rocker bottom soles), Masai Barefoot Technology®: MBT (similar to SW in form and material), more conventionally soled shoes with a typical toe-spring: MCS, and bare feet: BF) for 60s. The mean path length and mean velocity of Y (front-back) axis were significantly greater when wearing the MBT than when wearing the SW, and when wearing the SW than when BF or when wearing the MCS. In addition, mean velocity of X (left-right) axis, area surrounding root mean square, root mean square, and root mean square of Y-axis were significantly greater when wearing the MBT than when wearing the SW, MCS, or when BF. In conclusion, when wearing the MBT or SW with rounded sole, static standing posture becomes unstable because of their characteristics as compared with wearing MCS or when BF, but the MBT has a larger sway in the front-back direction than the SW.

Stimulus tempos and the reliability of the successive choice reaction test.

In ball game sports, players demand agility, which is a quick and adequate reaction to various changing stimuli. We developed a "successive choice reaction test" that evaluates such agility. This test requires subjects to be exposed to successive stimuli. Hence, it is very important to select appropriate stimulus tempos. In addition, it is necessary to examine the reliability of a new test. This study examined adequate stimulus tempos and test reliability. Fifteen healthy university students participated in this study. All the subjects conducted a successive choice reaction test with 3 kinds of tempos (1.3, 1.5, and 2.0 seconds). To examine its reliability, the test was conducted again on another day. It was found that any tempo has a high reliability, that their relationships are close, and insignificant time differences exist among the tempos. In conclusion, the successive choice reaction test was judged to be useful with any of the above tempos.

Gait characteristics when walking with rounded soft sole shoes.

This study aimed to examine the effect of shoes with a rounded soft sole (Stretch Walker: SW) on gait. Fifteen healthy male (mean age: 23.2) walked under three conditions (SW, Flat-bottomed Shoe: FS, Barefoot: BF). Including walking speed, stance time, step length were selected as temporal-spatial parameters. The angle of hip, knee, and ankle joints during particular phases were selected as kinematic parameters. Walking speed, stance time, step length and flexion angle of the ankle joint at initial contact were greater when wearing either shoe than walking BF; cadence was faster walking BF than wearing either shoe; double support time increased (FS>SW>BF); step width was greater (FS>SW>BF); walking angle was greater wearing the SW than wearing the FS and walking BF; and range of motion and maximum flexion angle of the hip and knee joints were greater wearing the FS than walking BF. In conclusion, wearing the SW with a heel-to-toe rocker and soft sole changes the double support time, step width, and walking angle and increases step length and walking speed compared to walking BF. The difference of the range of motion in hip and knee joints was larger between walking BF and wearing the FS than between walking BF and wearing the SW.

Comparison of the body-sway characteristics of young adults compared to healthy elderly and elderly with equilibrium disorder.

The study compared body-sway characteristics of 380 young adults, 342 generally healthy elderly without disequilibrium disorders, and a group of 33 elderly with disequilibrium disorders. Center of foot pressure (COP) was measured for 1 min. using an Anima's stabilometer G5500 with a data sampling frequency of 20 Hz. Four high reliability measures were used to evaluate body sway (unit time sway, front-back sway, and a left-right sway, and high frequency band power). Unit time sway, left-right sway, and high frequency band power were significantly larger for the group of elderly with disequilibrium disorders, and smaller for the healthy elderly people and young adults, in that order. Front-back sway was significantly larger in the elderly with disequilibrium disorders and healthy elderly than in young adults. The elderly with disequilibrium disorders had a larger and faster sway than young adults as well as the healthy elderly, particularly in the left-right direction. It appears aging was specifically associated with larger influence on the front-back sway.

Proposal for a new body sway evaluation method.

This study is aimed at examining body sway factors for 1107 healthy people aged 16 to 69 years and to propose a practical body sway evaluation method. The center of foot pressure measurement was carried out twice for 1 min. with a 1-min. rest. 30 parameters with high reliability selected from 6 domains (distance, distribution of amplitude, area, velocity, power spectrum, and body sway vector) were summarized objectively into 4 body sway factors (unit time sway, front-back sway, left-right sway, and high frequency band power). Factor scores were calculated by the estimate equation and the total standard scores of parameters with high factor loadings. Considering this result, a total standard score for each factor was classified into 4 percentile categories based on percentile rank. Using this classification criteria, body sway scores for each individual were classified into any of the above 4 domains for each factor. It was confirmed that young adults mainly belong to percentile Categories A and B and the elderly mainly belong to percentile Categories C and D. It was found that a great effect on body sway occurred when an individual's conscious condition changed (contracting a cold or after exercise). In conclusion, the body sway of healthy people can be explained by these 4 sway factors. An evaluation of the body sway pattern using the 4 sway factors may enable us to concretely understand individuals' disorders and abnormal states in addition to changes in body sway that occur with aging.

Age-stage differences in body sway during a static upright posture based on sway factors and relative accumulation of power frequency.

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.

Body-sway characteristics during a static upright posture in the elderly.

AIM: This study aimed to determine the reliability and sex and age-level differences of body-sway parameters, based on center of pressure (COP) measurements, during a static upright posture in the elderly and to clarify their body-sway characteristics in comparison with those of young adults. METHODS: The subjects were 50 healthy elderly and 50 healthy young adults. They had no evidence or known history of disorder. The data sampling frequency was 20 Hz. Thirty-six highly reliable parameters were selected from the following seven domains: distance; position; distribution of amplitude; area; velocity; power spectrum; and vector. In addition, four body-sway factors (unit time sway, front-back sway and a left-right sway and the high-frequency band power) were also measured. RESULTS: In the elderly, most body-sway parameters had very high reliability and did not show significant sex or age-level differences. The degree of body sway was greater in the elderly than in young adults, and marked differences were found, especially in sway velocity and periodicity. The four body-sway factors showed almost the same tendency as the 32 sway parameters. CONCLUSION: We judged that the body sway in the elderly showed large individual differences. Approximately 10% of the elderly subjects may be outside the standard range as compared to young adults, mainly in parameters relating to velocity and spectrum. Because the body-sway characteristics of the elderly are considerably different from those of young adults, we may need unique criteria to evaluate their body sway.

Power spectrum characteristics of sway position and velocity of the center of pressure during static upright posture for healthy people.

This study assessed sex and individual differences in sway-position and velocity power spectra and reliability of power frequency with 30 health young people. The body sway for 1 min. was measured twice over a 1-min. rest. There were no significant sex differences in the spectra. Frequency bands with a large coefficient of variance over 10.0 appeared up to 0.6 Hz. 75% relative accumulated power frequency appeared at 1.10-1.23 Hz in the position and at 2.00-3.05 Hz in the velocity spectra. Most power was in the low frequency band (A and B frequency intervals) of the international standard. Relative accumulated power frequency of position and velocity power spectra was reasonably reliable. It may be necessary to establish a new evaluation frequency interval by direction of sway-position and velocity using relative accumulated power frequency for healthy people.

Attention of postural control on foot somatosensor disturbance caused by the compression of blood vessels.

This study aimed to compare the center of foot pressure (CFP) during different ischemia periods by cuff compression. Ten healthy young adult males held their CFP for 1 min before and after cuff compression (250 mmHg) of lower limb blood vessels during two different compression periods (10 min and 26 min). Two-point discrimination thresholds and electric stimulus perception thresholds of each subject's right foot sole were measured during cuff compression to examine changes in the perceived level of cutaneous and proprioceptive sensation by blood flow inhibition. In addition, oxygenation kinetics in the anterior tibial muscle tissue was examined by near-infrared spectroscopy during cuff compression. The CFP was evaluated by using 36 parameters. CFP deflection tended to increase after cuff compression and to be larger over a long ischemic time (26 min) as compared with a short ischemic time (10 min). The proprioceptive perception threshold using electric stimulation showed a significant interaction and was higher after 26 min ischemia than at the initial timepoint and after 10 min ischemia. The delta[Oxy Hb/Mb], delta[Deoxy Hb/Mb] and Tissue oxygenation index (TOI) changed significantly after both ischemic conditions than at the initial condition. There was no significant difference in the Tissue oxygenation index and delta[Deoxy Hb/Mb] between both ischemic conditions. Many parameters regarding the deflection velocity and anteroposterior and lateral deflection had significantly larger values after 26 min ischemia than at the initial time point and after 10 min ischemia. Postural deflection may not be affected by the oxygen deficiency of muscle tissues caused by the compression of blood vessels for 10 min, but strongly affected by the cutaneous and proprioceptive sensation disturbances occurring from compression lasting over 10 min.

Segmental body composition assessment for obese Japanese adults by single-frequency bioelectrical impedance analysis with 8-point contact electrodes.

This study aimed to determine the accuracy of segmental body composition variables estimated by single-frequency BIA with 8-point contact electrodes (SF-BIA8), compared with dual-energy X-ray absorptiometry (DXA). Subjects were 72 obese Japanese adults (43 males and 29 females) aged 30 to 66 years. Segmental body composition variables (fat free mass: FFM, fat mass: FM, and percent fat mass: %FAT) were measured by these techniques. The correlations between impedance values and FFM measured by DXA were calculated. To examine the consistency in predicted values (SF-BIA8) with the reference (DXA), significant mean differences were tested by t-test and the degree of the difference was assessed by effect size. Correlations between the reference and predicted values were calculated. Additionally, the standard error of estimation (SEE) when estimating the reference from the predictor and the relative value of the SEE to the mean value of the DXA measurement (%SEE) were calculated. Systematic error was examined by Bland-Altman plots. High correlations were found between impedance and FFM measured by SF-BIA8. FFM in the extremities showed high correlations with the reference values, but systematic error was found. SF-BIA8 tended to overestimate FFM in the trunk. The consistencies in %FAT and FM with the reference value are inferior to those for FFM, and SEE values in %FAT and FM were greater than those for FFM. The accuracy of the estimated values in the trunk (FFM, %FAT, and FM) are inferior to those of the total body and extremities.

Comparison of power spectrum characteristics of body sway during a static upright standing posture in healthy elderly people and young adults.

This study was designed to compare peak frequency, mean power frequency, and power spectrum of each frequency band of body-sway time series and velocity time series power spectra between 30 healthy elderly people and 30 young adults and to clarify their frequency characteristics. Peak frequency and mean power frequency differed between groups, being higher for elderly persons, and the difference was marked in the front-back direction. When comparing power spectra of three domains (A: 0.02-0.2 Hz, B: 0.2-2.0 Hz, and C: 2.0-10.0 Hz) of an international standard, a significant age-group difference was found only in the front-back direction. Young adults were higher in the low frequency band (A domain) in sway time series, and the elderly group was higher in the high frequency band (C domain) in body-sway velocity time series. However, almost all power spectra of both groups appeared in the low frequency band. The present results suggested frequency characteristics of healthy people occur in the low frequency band, but the elderly group compared with the young adults had more characteristics in the high frequency band. Their frequency characteristics cannot be properly evaluated by the international standard established to screen disorders. It may be necessary for healthy people to have new evaluation frequency sections when considering power spectrum characteristics of sway time series and sway-velocity time series.

Residual volume on land and when immersed in water: effect on percent body fat.

There is a large residual volume (RV) error when assessing percent body fat by means of hydrostatic weighing. It has generally been measured before hydrostatic weighing. However, an individual's maximal exhalations on land and in the water may not be identical. The aims of this study were to compare residual volumes and vital capacities on land and when immersed to the neck in water, and to examine the influence of the measurement error on percent body fat. The participants were 20 healthy Japanese males and 20 healthy Japanese females. To assess the influence of the RV error on percent body fat in both conditions and to evaluate the cross-validity of the prediction equation, another 20 males and 20 females were measured using hydrostatic weighing. Residual volume was measured on land and in the water using a nitrogen wash-out technique based on an open-circuit approach. In water, residual volume was measured with the participant sitting on a chair while the whole body, except the head, was submerged . The trial-to-trial reliabilities of residual volume in both conditions were very good (intraclass correlation coefficient > 0.98). Although residual volume measured under the two conditions did not agree completely, they showed a high correlation (males: 0.880; females: 0.853; P < 0.05). The limits of agreement for residual volumes in both conditions using Bland-Altman plots were -0.430 to 0.508 litres. This range was larger than the trial-to-trial error of residual volume on land (-0.260 to 0.304 litres). Moreover, the relationship between percent body fat computed using residual volume measured in both conditions was very good for both sexes (males: r = 0.902; females: r = 0.869, P < 0.0001), and the errors were approximately -6 to 4% (limits of agreement for percent body fat: -3.4 to 2.2% for males; -6.3 to 4.4% for females). We conclude that if these errors are of no importance, residual volume measured on land can be used when assessing body composition.

Characteristics of body excursion during a static upright posture in elderly people with central nervous system disorders and with other disorders from the viewpoint of body-excursion parameters.

This study aimed to compare characteristics of body excursion of healthy elderly and elderly people with disorders. The participants were 38 healthy elderly who were at home (Healthy Elderly group) and 24 elderly people with disorders. The latter consisted of two groups: 12 in the Central Nervous System Disorders group with vestibular organ or central nervous system disorders, and 12 in the Other Disorders group with other system disorders. 34 parameters were selected from six domains: distance, distribution of amplitude, area, velocity, power spectrum, and vector. When compared with the Healthy Elderly group, the Central Nervous System Disorders group was judged abnormal on many parameters and showed large and quick body excursion characteristics, particularly in left-right excursion. The Other Disorders group showed different characteristics in the size of the left-right excursion and velocity of the front-back excursion. However, compared with the Central Nervous System Disorders group, very few people in the Other Disorders group were judged abnormal, and they showed slower velocity for front-back excursion.

Selection of useful parameters to evaluate center-of-foot pressure movement.

This study aimed to objectively summarize the parameters for evaluating the center-of-foot pressure and to select useful parameters with high reliability and validity with 220 healthy university students. In addition, 50 healthy university students were selected to examine cross validity. The measurement of center-of-foot pressure was carried out 3 times with a 1-min. rest and the mean of Trials 2 and 3 was used for the analysis. The data sampling frequency was 20 Hz. 34 parameters were selected from 6 domains: distance, distribution, area, velocity, spectrum, and vector. As a result of factor analysis the following four factors were interpreted: unit time sway, front-back sway, left-right sway and high frequency band sway. Their intraclass correlation coefficients were very high (ICC=.89-.95). Five parameters representing each factor were selected using stepwise selection by regression analysis. There were no significant differences between the mean factor scores estimated by the above five parameters in the original and in cross-validity groups, and relationships between factors in both groups were very high. The center-of-foot pressure may be predicted and systematically evaluated by the above four factors. Five parameters selected from each factor are considered to be useful ones with high validity and practicability.

QOL models constructed for the community-dwelling elderly with ikigai (purpose in life) as a composition factor, and the effect of habitual exercise.

The purpose of this study was to construct QOL models for the elderly that included ikigai as a composition factor and to clarify differences in two kinds of models, one constructed for the elderly with habitual exercise and the other for those without it. The subjects were 1,566 healthy community-dwelling independent people aged 60 years or more (752 males, 814 females). First, the ratio of subjects with ikigai was calculated. The ratios of subjects with different kinds of objects of ikigai were also calculated. Next, structural equation models (SEM) were constructed on the basis of social, physical, and mental QOL and ikigai. Fits of the models were evaluated. To examine whether the presence or absence of habitual exercise caused any difference in the QOL model, subjects were divided into 4 groups according to whether they were male or female and whether they had or did not have an exercise habit. Multi-population group simultaneous analysis was then performed among the four groups. More than 85% of the subjects had objects of ikigai. Ikigai is an important factor for comprehending the QOL of the elderly. It was possible to construct QOL models for the elderly with ikigai as a composition factor. The effect of physical QOL on mental QOL was negligible in females irrespective of whether they had an exercise habit. The effect of social QOL on mental QOL was profound in aged females with an exercise habit. The effect of the living situation on mental QOL was profound in aged females without an exercise habit. The effect of mental QOL on ikigai was more marked in subjects without an exercise habit than in those with an exercise habit.

Body sway characteristics during static upright posture in healthy and disordered elderly.

This study aimed to compare body sway characteristics of the healthy elderly and the disordered elderly. The subjects were 38 healthy elderly and 24 disordered elderly with disequilibrium. The latter consisted of two groups: 12 elderly with vestibular organ or central nervous systems disorder (central nervous disorders), and 12 elderly with disorder in other systems (other disorders). The measurement device can calculate the center of foot pressure (CFP) of vertical loads from the values of three vertical load sensors, which are located at the corners of an isosceles triangle on a level surface. The data sampling frequency was 20 Hz. Four body sway factors with high reliability (unit time sway, front-back sway, left-right sway, and high frequency band power) were used to evaluate body sway. As compared with healthy people, central nervous disorders had larger unit time sway, high frequency band power, and left-right sway factors. Other disorders were larger in unit time sway and high frequency band power factors. Central nervous disorders, as compared with other disorders, had larger unit time sway and left-right sway factors. Disorders produced large and fast sway, and central nervous disorders in particular showed a marked sway in the left-right direction. The existence of disease influenced body sway more than decline in various functions related to posture control with aging, because even with the same elderly, disorders showed a larger body sway.

Gender and age-related differences of dynamic balancing ability based on various stepping motions in the healthy elderly.

This study was aimed at examining the gender and age-related differences of dynamic balance based on four stepping tests for the elderly. One hundred and eleven healthy subjects aged 60-85 were classified into four age groups (60-64, 65-69, 70-74, and 75-85) to examine age-related differences. They conducted stepping motions lasting 20-sec, including both-leg stepping right/left, both-leg stepping back/forth, one-leg stepping back/forth and one-leg stepping right/left. There were significant differences by age in all stepping parameters, with the decreasing number of steps and the increasing average ground connecting time during stepping with age. In males of age 60-69 and all females, the individual differences in the number of steps and the average connecting time during both-leg stepping (back/forth and right/left) were larger than those during one-leg stepping. Both-leg stepping was, therefore, considered to be a useful test to evaluate the individual differences of dynamic balance in the elderly. Individual differences in the number of steps by both-leg stepping tended to decrease with age. In males aged 70 or more, the individual differences in the number of steps and the average connecting time in both-leg stepping were smaller than those in one-leg stepping. The relationships between the results by both-leg stepping and those by one-leg stepping were poor. This may be because of the difference in body-posture stability during stepping motions. One-leg stepping is a useful test for the elderly who have difficulty with both-leg stepping because of its small center of gravity sway. The relationships between back/forth steps and right/left steps in both-leg or one-leg stepping were notable. Either of the stepping motions, therefore, can be selected to evaluate dynamic balance ability. There may be gender differences in the strategy to keep a stable body posture during both-leg stepping.

Relationships between force curves and muscle oxygenation kinetics during repeated handgrip.

The purpose of this study was to clarify the kinetics of muscle oxygenation by near infrared spectroscopy (NIRS) in the phase of the decreasing force, especially the pre- and post-phases of the inflection point, during repeated rhythmic grip (RRG) of 30 grips/min(-1) for 6 minutes. The inflection point was the time at which the decreasing speed of the grip force changed markedly. It was calculated statistically from two regression lines fitted to each decreasing phase by applying a two-phase regression model. Ten healthy males performed the RRG for 6 minutes. Total Hb and Oxy-Hb decreased rapidly about 10 sec (7.0+/-5.9 sec, 9.8+/-5.4 sec, respectively) corresponding to the value decreasing by 90% MVC after the onset of gripping. Deoxy-Hb was maintained at a high value for 76.2+/-27.9 sec, corresponding to the value decreasing by 70-80% MVC. These phases are considered to be the states where oxygen was not satisfactorily supplied to the active muscles because of the obstruction of blood flow caused by an increase in the intra-muscular pressure. Deoxy-Hb decreased for 120+/-21.3 sec after reaching the highest value, and then reached an almost steady state at a higher level than the rest. After this phase, muscle oxygenation kinetics enters the state where oxygen is satisfactorily supplied to active muscles. We considered that the relationship between oxygen supply and demand differs during the initial and the latter phases in RRG. The changing phase in the decreasing speed of the grip force, namely the inflection point of the decreasing force, significantly correlated with the changing phase of the Oxy-Hb and Deoxy-Hb kinetics. The inflection point of the decreasing force seems to correspond to the phase where oxygen supply cannot meet oxygen demand and the increase of Deoxy-Hb. We infer that the pre- and post-phases of the inflection point depend on different physiological factors.

Gender differences in body-sway factors of center of foot pressure in a static upright posture and under the influence of alcohol intake.

This study aimed to examine gender differences in 4 body-sway factors of the center of foot pressure (CFP) during a static upright posture and the influence of alcohol intake on them. Four body-sway factors were interpreted in previous studies using factor analysis (the principal factor method and oblique solution by promax-rotation) on 220 healthy young males and females as follows; unit time sway, front-back sway, left-right sway and high frequency band power. The CFP measurement for 1 min was carried out twice with 1 min rest. The measurements of blood pressure, heart rate, whole body reaction time, standing on one leg with eyes closed, and CFP were carried out before and after the alcohol intake using 11 healthy young males and females. The measurement device used was an Anima's stabilometer G5500. The data sampling frequency was 20 Hz. Reliability of 4 body-sway factors was very high. Significant gender differences were found in the left-right sway and the high frequency band power factors, but the influence on body-sway is, as a whole, can be disregarded. These four sway factors can determine the influence of alcohol intake as efficient as 32 sway parameters.

Influence of alcohol intake on the parameters evaluating the body center of foot pressure in a static upright posture.

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.