Masahiro Noda

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 Animas 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.

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 Animas 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.

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.

Comparison of quantitative analysis and fractal analysis of center of pressure based on muscle fatigue.

To examine the influence of muscle fatigue on center of pressure displacement during quiet standing using quantitative and fractal analyses, 12 healthy young men and women did the exercise stress test on the triceps surae muscle until fatigued. Subjects were measured for body stability for 60 sec. before and after the exercise. Quantitative analysis showed that center-of-pressure parameters for distance, velocity, amplitude distribution, and mean vector length of sway in the anterior/posterior direction changed significantly after muscle fatigue but not on the periodic parameters. This result suggested that quantitative analysis may identify the effects of muscle fatigue on the parameters that show displacement in the anterior/posterior direction of center of pressure. Fractal analysis indicated the value of critical point coordinates increased after muscle fatigue. This analysis can clarify the fundamental postural control strategy and time-series characteristics of postural sway which cannot be identified by spectral analysis.

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.

Influence of lower leg muscle fatigue on the centre of pressure in a static upright posture

Abstract We examined the influence of fatigue in the lower leg muscles on the centre of pressure sway during a static upright posture. Twelve healthy young men and women completed the exercise stress test on the triceps surae muscle and continued the exercise until their muscles were fatigued. A centre of pressure sway of 1 min was carried out in a Romberg posture at rest and at different instants after fatiguing exercise: immediately after, 5 min after, and 10 min after exercise. Blood lactate concentration was measured from fingertip samples taken before and immediately after exercise. To evaluate body sway, the following four centre of pressure sway factors were selected: unit time sway, front–back sway, left–right sway, and high-frequency band power spectrum. The measurement device used was an Anima stabilometer (G5500). The data sampling frequency was 20 Hz. After exercise, blood lactate concentration was increased. Significant differences were observed in unit time sway, front–back sway, and high-frequency band power spectrum immediately after exercise. These values eventually returned to baseline levels 5 min after fatiguing exercise.

Development of various reaction abilities and their relationships with favorite play activities in preschool children.

Abstract Miyaguchi, K, Demura, S, Sugiura, H, Uchiyama, M, and Noda, M. Development of various reaction abilities and their relationships with favorite play activities in preschool children. J Strength Cond Res 27(10): 2791–2799, 2013—This study examines the development of various reaction movements in preschool children and the relationship between reaction times and favorite play activities. The subjects were 167 healthy preschool children aged 4–6 (96 boys and 71 girls). This study focused on the reaction times of the upper limbs (reaction 1: release; reaction 2: press) and the whole body (reaction 3: forward jump). The activities frequently played in preschools are largely divided into dynamic play activities (tag, soccer, gymnastics set, dodge ball, and jump rope) and static play activities (drawing, playing house, reading, playing with sand, and building blocks). The subjects chose 3 of 10 cards picturing their favorite play activities, depicting 10 different activities. All intraclass correlation coefficients of measured reaction times were high (0.73–0.79). In addition, each reaction time shortened with age. Reaction 1 showed a significant and low correlation with reaction 3 (r = 0.37). The effect size of the whole body reaction time was the largest. Whole body reaction movement, which is largely affected by the exercise output function, develops remarkably in childhood. Children who liked “tag” were faster in all reaction times. The children who chose “soccer” were faster in reactions 2 and 3. In contrast, children who liked “playing house” tended to have slower reaction times. Dynamic activities, such as tag and soccer, promote development of reaction speed and agility in movements involving the whole body. Preschool teachers and physical educators should re-examine the effect of tag and use it periodically as one of the exercise programs to avoid unexpected falls and injuries in everyday life.

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.