ABSTRACT
We carried out three measurements on 12 healthy men to investigate the positional perception in forward or backward flexions of the trunk while standing. In measurement (I), the subjects reproduced the target angle perceived by forward flexion (FF) or backward flexion (BF) of the trunk with their eyes blindfolded. In measurement (II), the subjects first visually perceived the angle shown by an angular, indicator, and then reproduced it by manually by operating the indicator with their eyes open. In measurement (III), the subjects first visually perceived the angle shown by an angular indicator, and then expressed the target angle by FF or BF with their eyes blindfolded. In measurements (I) and (III), indication of the target angle was set at in 5° increments from 5° to 60° in FF, and from 5° to 30° in BF, and in measurement (II) from 5° to 60°. The ability of positional perception was evaluated using the constant error (CE) and the absolute error (AE) of the reproduced or expressed angle.<BR>In measurement (I), CE was small for all target angles, ranging from -0.2°to 2.6°in FF and from 0.3°to 1.6°in BF. However, CE from 5° to 25°in FF was significantly positive. In BF, significant CE was not recognized for any target angles, and AE at each target angle was smaller than that in FF. These results suggest that the sensitivity of positional perception of the trunk in FF is relatively low for small target angles which are close to the quiet standing position.<BR>In measurement (II), CE was very small for all target angles, ranging from -1.2° to 0.9°. Significant CE was recognized only at 10°, 20°and 55°. AE was also small for all target angles, ranging from 0.5° to 1.8°, and no significant difference in AE was recognized among the target angles. These results suggest that visual perception, memorization and recall of the target angle is well retained.<BR>In measurement (III), a relationship between the target angle and the CE was shown on a negative regression line in both FF and BF. As viewed from the regression line, the angle at which the CE became zero was 36°in FF and 18° in BF. AE in target angles close to these angles was also small. This indicates that angles smaller than these are perceived as smaller than they actually are, while angles larger than these are perceived as larger than the actual ones.
ABSTRACT
This study focused on the effect of pressure sensation from the each plantar surface of the feet on postural control. The plantar surfaces of the feet were made less sensitive by cooling, using a specially designed apparatus set on a force plate. Three areas were cooled: the plantar surface of the heel, the forefoot, and the entire plantar surface of the foot. And the non-cooling condition was the control. The subjects, seven healthy men, were asked to track a continuously moving target spot displayed on a visual monitor while standing on the force plate. This tracking was done by controlling the center of foot pressure (CFP) by leaning forward and backward at the ankles. The target was moving at 0.025 Hertz (once per 40 seconds) with a triangular waveform. The moving range of the target was from 30 to 70 percent (%) of the total foot length from the heel, and this range was divided into 10 percent (%) subranges. Postural controllability was evaluated by the difference between movements of the CFP and target for each subrange. When the entire surface of the foot was cooled, postural controllability of moving the CFP anteriorly was significantly worse than the control. Postural controllability of moving the CFP anteriorly for the anterior and the posterior moving subranges was significantly worse than the control when the heel was cooled. When the forefoot was cooled, postural controllability of moving the CFP anteriorly for the anteriorly moving subrange was significantly worse than that of the control. These results suggest that pressure sensation from the plantar surface definitely participates in moving the CFP anteriorly for postural control. When the CFP is situated on the heel, pressure sensation from the heel alone may play a necessary role for postural control. When the CFP is situated on the forefoot, however pressure sensation from the forefoot may need to be the supplemented by sensation from the heel for adequate postural control.
ABSTRACT
A study was conducted to investigate the influence of motor learning on functional specialization of the upper and lower limbs by comparing automatized levels in upper and lower limb movements between 17 soccer (S group) and 14 basketball (B group) players at a university. They carried out transitory palmar flexion of both hands while stepping and performing alternate flexion-extension movements of both ankle joints, and transitory plantar flexion of both feet while performing alternate flexion-extension movement of both shoulder joints and both wrist joints. The automatized levels of the upper and lower limb movements were evaluated by the degree of interference between the upper and lower limb movements.<BR>It was shown that automatization of lower limb movements was more advanced than that of upper limb movements in both groups. The automatized levels of stepping in the S and B groups showed no significant difference, and were similar to those of university students in general obtained in our previous study. However, the automatized levels of ankle joint movements in both groups were higher than those for university students in general.<BR>In both groups, the insertion of transitory palmar flexion was restricted to within the phase where the degree of interference was small during the stepping and ankle joint movement. However, this tendency was not clear in the trial where transitory plantar flexion was superimposed on shoulder joint and wrist joint movements.<BR>As for the difference between the groups, the S group showed a higher automatized level of ankle joint movement than the B group. On the other hand, the B group showed higher automatized levels of both upper limb movements than the S group, and this tendency was especially evident for shoulder joint movement.<BR>These results suggest that the change in the automatized level of upper and lower limb movements by specific motor learning is added to the functional specialization of the upper and lower limbs acquired by daily basic motor learning in an upright position.
ABSTRACT
The purpose of this study was to evaluate the relationship between the position of the center of foot pressure (CFP) and control of standing posture in ten healthy men by tracking the CFP to the moving target.<BR>Subjects were required to track a continuously moving target displayed on a screen while standing on a force plate. The velocity of the target movement was 0.05, 0.10, and 0.15 hertz (Hz) with a triangular waveform. The target was moved 30-70% within the range of the heel regarding the foot length as 100%, and the range was divided by 10%. Each subrange was named (A), (B), (C), (D) for backward movement from 70% to 30%, and (E), (F), (G), (H) for forward movement from 30% to 70%.<BR>The standing posture control was analyzed by mean error and absolute error at turning point between target- and CFP-movement.<BR>The mean error of backward movement was significantly greater than that of forward movement in the two forward subranges at 0.15 Hz. As for the other frequencies, there was no significant difference between directions of CFP movement. Mean error of A was significantly greater than that of B and C in higher frequencies, but there was no significant difference at 0.05 Hz. Regarding absolute error, there was no significant difference between the forward and backward turning point with a decrease in frequency. Mean error of D or E was greatest among the section in all frequencies. The ratio of the greater D or E and A or H was greatest at 0.05 Hz.<BR>These results suggested that CFP tracking at 0.05 Hz is hardly influenced by direction and velocity of the target movement. Terefore, we conclude that controllability of the stand-ing posture differs markedly in various CFP positions. In addition, control of the standing posture in a backward direction is inferior to that in a forward one.
ABSTRACT
A study was conducted to investigate the effects of a sagittal position of the body gravity center (GCP) and manual weight-load on postural control during rapid arm-lifting. The subjects were five males aged 21 to 36 years. They stood on a force plate while maintaining the GCP at 30%, 45% and 60% from the heel, regarding the fool length as 100%, and anteriorly lifted both arms spontaneously as rapidly as possible. These trials were carried out ten times under a 5 kg weight or no weight. EMGs of the biceps femoris muscle (BFM) and anterior deltoid muscle (ADM), the fluctuation of the center of foot pressure (CFP) and body motion were analyzed by focusing on their time sequences.<BR>At 45% and 60% GCP the BFM action started prior to the ADM action, whereas at 30% GCP it tended to lag behind. The lag times under no weight were 13.9±12.75 ms (mean±SD) at 30% GCP, -32.7±18.18 ms at 45% GCP and -46.0±19.40 ms at 60% GCP. Those under 5 kg weight were 15.0±11.40 ms at 30% GCP, -22.0±6.74 ms at 45% GCP and -28.9±7.63 ms at 60% GCP. These results indicate that the anticipatory action of the muscle related to postural control arises only at specific GCPs.<BR>The difference of starting points for BFM action to ADM action showed no significant difference between 45% and 60% GCP for either as 5 kg or no weight. The CFP position moving in a forward direction during arm-lifting showed a marked difference between 45% and 60% GCP. The time for arm-lifting showed a marked difference between 5 kg and no weight. These results suggest that the starting point of anticipatory muscle action related to postural control does not change according to the magnitude and time course of the distance to the body equilibrium as a result of arm-lifting.
ABSTRACT
The voluntary exercises consist of different automatized levels and are mostly a combination of the upper limbs and the lower limbs exercises.<BR>This study was to examine the interference of the upper limbs exercise to the periodic lower limbs exercise with different automatized levels. Seven male university students, aged 19 and 20 yrs., served as subjects. The periodic lower limbs exercises were the stepping (walking on the place) and the alternate plantar-flexion of the right and left foot while standing. The frequencies of the lower limbs exercises were 120, 160 and 200 times/min, The stepping, which is similar to the motion of the lower limbs in walking or running, may be performed more frequently in daily life than the plantar-flexion in which only the ankle angle was changed. Therefore, we assume that the stepping is a higly automatized exercise compared with the plantar-flexion. Upper limbs exercise, which was combined with the lower limbs exercise, was the simultaneous tapping of one time by both hand. The interference degree was evaluated by the change of step intervals of the lower limbs exercise. The results were:<BR>1) The fluctuation of step intervals on the plantar-flexion was greater than the fluctuation on the stepping and the smallest in the frequency 120 compared with that in the other frequencies.<BR>2) When the tapping was combined with the lower limbs exercises, one step interval at that time was lengthened and one step interval immediately before the tapping was shortened. This change of step intervals was greater in the plantar-flexion than that in the stepping. The change in the plantar-flexion was the smallest in the frequency 120 compared with that in the other frequencies.<BR>The above mentioned findings suggest that the automatized level of the lower limbs exercise can be clearly evaluated by the interference degree of the upper limbs exercise to the periodic lower limbs exercise.
ABSTRACT
This study was designed to investigate the change of postural control while repeatedly imposing the horizontal floor vibration in upright stance. A vibration table mounted with a force platform was vibrated sinusoidaly in anteroposterior direction under the condition of 2.5 cm amplitude and 0.5 Hz frequency. Ten female subjects, aged from 18 to 21 years, were equally divided into O-group and C-group. The subjects maintained the standing posture on the vibration table, for one minute with open and closed eyes in both groups in the first trial, for two minutes with open eyes in O-group and with closed eyes in C-group in the 2 nd to 11 th trials, and for one minute with closed eyes in O-group and open eyes in C-group in the 12th trial. The fluctuation of the center of foot pressure (CFP) in anteroposterior direction and EMGs of m. tibialis anterior and m. gastrocnemius were analyzed. The controllability of standing posture was evaluated by the mean speed of the CFP fluctuation. The muscle activity was examined with EMGs. The results were summarized as follows :<BR>1) In a great number of subjects, the controllability of standing posture rapidly improved till the 3rd trial in each eye condition, while after the 3 rd trial changes of controllability were relatively small. Accordingly, it was suggested that by investigating the change of controllability for 5 trials, we could sufficiently detected an individual difference of the learning ability of postural control.<BR>2) At the beginning of the practice, the controllability with open eyes was greatly superior to that with closed eyes. Although the difference of controllability between open and closed eyes decreased with advance of practice, in the 11 th trial that difference was obviously observed.<BR>3) In a great number of subjects, the phase lag of the CFP fluctuation to the floor vibration increased till the 3rd trial according to improving controllability. In some subjects, the change of controllability was relatively small, the change of phase lag was small and also, correlations between the postural controllability and the phase lag weren't significant.<BR>4) M. gastrocnemius was active when the CFP fluctuated forward and m. tibialis anterior when the CFP fluctuated backward greatly. In each eye condition, the magnitude of muscle activity decreased with practice and m. tibialis anterior was inactive in a great number of subjects in the last stage of the practice.<BR>5) The controllability with open eyes didn't show a significant change after practice with closed eyes. By contrast, the controllability with closed eyes improved greatly after practice with open eyes and was approximately equal to that in the last stage of practice with closed eyes.