[The influence of the leg load and the support mobility under leg on the anticipatory postural adjustment].

Anticipatory postural adjustment is an essential part of equilibrium maintainance during standing in human. So changes in stance condition could affect both control of equilibrium and anticipatory adjustment. Anticipatory changes in the stabilogram of each leg were studied in standing subject during the early stage of quick right arm lifting while legs were on two separated supports. The center of pressure (CP) movement was analyzed in three variants of experiment: both legs on immovable support, with only right leg on the movable support and with only left leg on the moveable support. In each standing condition subject stood with symmetrical load on two legs or with the load voluntary transferred to one leg. The anticipatory CP shift depended on the mobility of the support under the leg and on loading of the leg. While standing on unmovable supports with symmetrical load on the legs before lifting of the right arm CP of right leg shifted backward and CP of left leg--forward. While standing with one leg on movable support the anticipatory CP shift of this leg was small and did not depend on the load on the leg. However the shift of CP of the leg that was placed on the unmovable support depended on the load in the same way as in the case when both legs were on unmovable supports. Results suggested that since on movable support the support and proprioceptive afferent flow from distal part of the leg that was did not supply unambiguous information about body position, the role of distal joints in posture control is reduced.

[Influence of Achilles tendon vibration on the human vertical posture during standing with asymmetrical leg loading].

The shift of center of pressure (CP) of body and CP of each leg was studied during Achilles tendon vibration of one or both legs while subject was standing with symmetrical load on the legs or with the load transferred on one leg. The CP shift of standing subject during unilateral Achilles tendon vibration depended both on the side of the tendon vibration and on the leg load. When standing with a load transferred on one leg the shift of common CP was larger than when the vibration was applied to the loaded leg. The CP shift of one leg was greater if the vibration, and the load was applied to it. Vibration of unloaded leg caused a CP shift in the contralateral loaded leg. In this case, the vibration of left unloaded leg caused no noticeable CP shift of left leg, while the vibration of the unloaded right leg caused CP shift of right foot. In the same conditions of load and vibration the CP displacement of right leg was larger than the CP shift of left foot. It can be assumed that the change in the load on the leg and unilateral vibration of leg muscles change of the internal representation of the vertical body axis, which affects the CP position of one leg during the muscles vibration.

[Influence of the movable support under one leg on human vertical posture during standing with asymmetric load on legs].

The posture in standing subjects was studied when the legs were placed on supports of different degrees of mobility, as well as, when a part of body weight was voluntary transferred to one leg. The aim of these experiments was to explore how the mobility of support under the feet affects the balance and how this influence could be changed by the load distribution between the legs during standing. When both legs were on rigid immovable supports, the posture maintaining was accomplished by control of center of pressure (CP) of both legs. When the subject transferred the weight on one foot the posture was maintained mainly due to the control of CP of loaded leg. When the legs were on the supports of different mobility, the balance was maintained by the control of CP of the leg on the immovable support. This result was observed both when the subject stood with symmetric load on the legs and when the load was transferred to one leg. Even when the leg was unloaded but was placed on immovable support its CP moved more in comparison with the CP of loaded leg on movable support. The results show that the support mobility under the legs is a factor that determines the mechanisms of the posture maintenance, and this factor is more significant than the load distribution between the legs. So, we can conclude that the upright posture is maintained accounting the physical properties of the supports under the feet.

[Characteristics of vertical posture maintenance during standing with asymmetrical legs loading].

We studied the motion of the common center of pressure (CP) and of right and left foot CP, while maintaining a vertical posture when standing with symmetrical legs loading and with the transfer a part of weight to the right and left leg. It was shown that when standing with symmetrical legs loading the single leg CP motion occurred along a straight line with small side deviations in contrast to common CP motion, which was along an irregular curve, which often changed the direction and covered some area. When weight was transferred on one leg the motion of CP of loaded leg was similar to the motion of CP of that leg during standing with symmetrical load. The motion of CP of unloaded leg was along an irregular curve. During standing with weight transferred on one leg, the correlation between the CP movements of the left and right foot was reduced compared to standing with symmetrical load on thelegs. The velocity of loaded leg CP increased in the sagittal direction, but did not change inthe frontal direction. The velocity of unloaded leg CP motion did not change in the sagittal direction, and increased in the frontal. It was suggested that during standing with asymmetrical load on legs the involvement of the leg in maintaining the vertical posture depends on the load supported by this leg.

[Influence of an additional movement task for the upper extremities on equilibrium maintenance in frontal and sagittal level in standing man].

The postural oscillations of standing man were studied during additional manual motor task that consisted of maintaining of the moving ball in the center of flat box. The movement of a center of pressure (CP) in frontal and sagittal plane were analyzed during standing on stable rigid support and on moving unstable support. The influence of the additional motor task on CP movement depend on level of support stability. Sagittal CP movement increased while the additional task was executed during standing on moving support but it did not when the support was stable. Frontal CP movement decreased when the additional task was executed during standing on stable support but it did not while the support was unstable. Thus execution of the additional motor task execution led to the reduction of efficacy of the postural control on the moving unstable support. This result suggests that the cortical influence on the postural mechanism was stronger during standing on moving support in comparison to the standing on the stable support.

[Pathological tonic reflexes in adolescents with infantile cerebral palsy]. / Patologicheskie tonicheskie refleksy u podrostkov, bolnykh detskim tserebral'nym paralichom.

A study was made of pathological tonic reflexes (PTR) in adolescents afflicted with infantile cerebral paralysis (ICP) by means of assaying the tone of thigh muscles before and after treatment and in the presence of L-DOPA (nacom, 62.5 mg/day) intake. The drug minimized the manifestations of PTR because of changes in the function of brain structures involved in tonic reactions. It is recommended that during establishment of indications for +orthopedic-surgical treatment of ICP patients with marked PTR determining the formation of reflex contractures and deformities of limb joints, conservative treatment with L-DOPA drugs be preliminarily carried out.

[Dependence of muscle electrical activity on its length in the development of a constant force]. / Zavisimost' élektricheskoi aktivnosti myshtsy ot ee dliny pni razvitii postoiannoi sily.

Dependence of the integrated electromyogram on the muscle length with its tension being constant was investigated in human biceps muscle. The subject kept his forearm at known angles or flexed the elbow at the horizontal plain against a constant force applied to his wrist. The data obtained showed that the integrated electromyogram increased several times with muscle shortening both at static condition and during movement. Causes of increase in the electrical activity are discussed.