Development of body equilibrium control in elementary school children was examined by analysing movement of the center of gravity (CG) during maintenance of an upright stance under various visual conditions. Eightyfour healthy subjects aged 7 to 12 years were instructed to stand in the Romberg position on a force plate for 30s with the eyes open, eyes closed, or eyers restricted to a 15-degree visual field. The length of trace, root mean square (RMS), and the power spectra of fore-aft CG movement were calculated by a personal computer.
The results were as follows;
1. The length of trace and RMS of CG increased in accordance with the decrease in the amount of visual information, and consequently increased in order: eyes closed, restricted visual field, eyes open.
2. The length of trace and RMS of CG for boys decreased with increasing age, but none of these factors in girls was related to age.
3. The power spectrum analysis of CG movement showed a peak of power at 0.4 to 0.7 Hz during both eyes closed and eyes restricted.
4. This feature was shown in all age groups for girls, but only in the 11 to 12-year age group for boys.
5. The greater the decrease in the length and the RMS of CG with increasing age, the higher the amplitude of the power spectrum peak.
In conclusion, it was clarified that stability of posture in elementary school children is dependent upon the amount of visual information. The characteristics of the change in frequency zone manifested by decreasing the amount of visual information may reflect the developmental process of visual postural control in children.

The purpose of this study was to examine the effect of hopping tempo on the stretch reflex of the soleus muscle at the landing phase during continuous hopping. The M 1 and M 2 components of stretch reflex of the soleus muscle and angular velocity of the ankle joint were recorded at the landing phase during hopping under four hopping tempos with frequencies of 1.0, 1.5, 2.0, and 2.5 Hz. The electromyogram (EMG) activities in the soleus muscle during the landing and the jumping phases were separated under 1.0, 1.5 and 2.0 Hz conditions, but EMG's for both phases were overlapped under 2.5 Hz condition. Furthermore, at 1.0 and 1.5 Hz, a non-active EMG phase was observed between the landing and the jumping phases ; but this non-active phase disappeared at 2.0 Hz. The M 1 and M 2 components at 2.0 Hz showed significantly (p<0.01) larger values than those at 1.0 and 1.5 Hz. However, there was no significant difference observed between the components at 1.0 and 1.5 Hz. The M 2 component showed a significantly (p <0.01) smaller value than the M 1 component at 1.0 and 1.5 Hz ; but there was no significant difference at 2.0 Hz. The angular velocity of the ankle joint showed no significant difference under any of the conditions. These findings suggest that stretch reflex at landing during hopping may be inhibited at the motion pattern of the inactive phase between the landing and the jumping phases in EMG's. In addition, the stretch reflex is not only related to mechanical muscle stretching, but is also under the influence of the superior nerve center.

Purpose: The purpose of this study was to examine the influence of the exercise program for Osteoarthritis of the knee (knee OA) which American Geriatrics Society Panel on Exercise and Osteoarthritis (AGS) recommends on physical function in Japanese independent elderly with knee joint pain.Methods: Subjects of this study were 36 (7 males : aged 74.7±5.1 years, 29 females : aged 72.3±4.6 years) community-dwelling independent elderly with knee joint pain who voluntary participated in our exercise program. The program consisted of massage around knee, flexibility exercises in knee and ankle joints, and leg muscle development exercises. They performed these exercises twelve times for a month at regular intervals. Physical function were evaluated by the muscle strength during knee extension and flexion, the range of motion of knee joint and the center of pressure during upright standing. There were three times measurements at one month before starting of the program (the 1 st), immediately before beginning of the program (the 2 nd), and just after ending of the program (the 3 rd). Difference between change in measurement values during the observation period (subtract the 1 st from the 2 nd ; Δ1) and that during intervention period (subtract the 2 nd from the 3 rd ; Δ2) were analyzed by Students't-test.Results and Conclusion: There was significant difference between Δ1 (0.01±0.05 kg/wt) and Δ2 (0.04±0.05 kg/wt) on maximal muscle strength during knee extension. This result suggested that the exercise program recommended by AGS was improved the leg muscle strength in Japanese elderly with knee joint pain. However the effects of the exercise intervention were not clarified on the other physical function. As for the reasons it seems to affect the initial level of joint pain and physical function in the subjects. Therefore, reexamination of this point with a greater number of samples which the worse level of knee joint pain is needed in the future.

The purpose of this study was to examine the effect of physical inactivity, produced by prolonged bed rest, on the excitability of the spinal motor neuron pool in humans, using the activity of soleus H-reflex.
Eight healthy male subjects underwent continuous bed rest with 6 degree head-down tilt for 20 days (BR group) . Ten different healthy male subjects maintained their usual daily life during the observation period for 20 days (control group) . Recruitment curves of H-reflex and M-wave were obtained from every subject. H slope/M slope (H slp/M sip) which shows the excitability of spinal motor neurons was calculated by using data in the recruitment curve.
The H sip/M sip in the BR group significantly increased after BR, compared to the pre-BR values (p<0.05) . In the control group, however, there were no significant differences in the H slp/M sip between the pre and the post-observation values. At the baseline, the H slp/M sip showed no significant differences between the BR group and the control group. After the BR, the H slp/M sip in the BR group significantly increased compared to the control group after the observation period (p<0.05) .
This study suggests that the excitability of the monosynaptic spinal motor neuron pool is facilitated by physical inactivity during BR.