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We saw that in quiet standing an ankle strategy applies only in the A/P direction and that a separate hip load/unload strategy by the hip abd/adductors is the totally dominant defence in the M/L direction when standing with feet side by side. In other standing positions (tandem, or intermediate) the two mechanisms still work separately, but their roles reverse. In the tandem position M/L balance is an ankle mechanism (invertors/evertors) while in the A/P direction a hip load/unloading mechanism dominates.
During initiation and termination of gait these two separate mechanisms control the trajectory of the COP to ensure the desired acceleration and deceleration of the COM. During initiation the initial acceleration of the COM forward towards the stance limb is achieved by a posterior and lateral movement of the COP towards the swing limb. After this release phase there is a sudden loading of the stance limb which shifts the COP to the stance limb. The COM is now accelerated forward and laterally towards the future position of the swinging foot. Also M/L shifts of the COP were controlled by the hip abductors/adductors and all A/P shifts were under the control of the ankle plantar/dorsiflexors. During termination the trajectory of both COM and COP reverse. As the final weight-bearing on the stance foot takes place the COM is passing forward along the medial border of that foot. Hyperactivity of that foot's plantarflexors takes the COP forward and when the final foot begins to bear weight the COP moves rapidly across and suddenly stops at a position ahead of the future position of the COM. Then the plantarflexors of both feet release and allow the COP to move posteriorly and approach the COM and meet it as quiet stance is achieved. The inverted pendulum model permitted us to understand the separate roles of the two mechanisms during these critical unbalancing and rebalancing periods.
During walking the inverted pendulum model explained the dynamics of the balance of HAT in both the A/P and M/L directions. Here the model includes the couple due to the acceleration of the weight-bearing hip as well as gravitational perturbations. The exclusive control of A/P balance and posture are the hip extensors and flexors, while in the M/L direction the dominant control is with the hip abductors with very minor adductor involvement. At the ankle the inverted pendulum model sees the COM passing forward along the medial border to the weight-bearing foot. The model predicts that during single support the body is falling forward and being accelerated medially towards the future position of the swing foot. The model predicts an insignificant role of the ankle invertors/evertors in the M/L control. Rather, the future position of the swing foot is the critical variable or more specifically the lateral displacement from the COM at the start of single support. The position is actually under the control of the hip abd/adductors during the previous early swing phase.
The critical importance of the hip abductors/adductors in balance during all phases of standing and walking is now evident. This separate mechanism is important from a neural control perspective and clinically it focuses major attention on therapy and potential problems with some surgical procedures. On the other hand the minuscule role of the ankle invertors/evertors is important to note. Except for the tandem standing position these muscles have negligible involvement in balance control. 相似文献
Dodecon, the soluble hemagglutinin present in all adenovirus types of subgroup II
Summary The sedimentation rate of the soluble complete hemagglutinins of 16 prototype adenoviruses of subgroup II were determined by means of sucrose gradient centrifugation. The rates were similar for all types (65±10S), thus indicating that the structural components may also be identicali.e. dodecon (1).
Durchgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft. 相似文献
Summary Antigens of adenovirus type 19 were concentrated by means of polyphosphate, a time-saving and mild procedure. Infectious virus, haemagglutinin and adenovirus group antigen were completely precipitated in a pH range between 2.8 and 3.6, when 2 mg. polyphosphate per ml. antigen was used. Under the same conditions, the bulk of total protein as well as of complement-fixing HeLa cell antigen was precipitated. Consequently, a concentration of virus-specific components was achieved, but no purification.
Durchgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft, Bad Godesberg.
Herrn Prof. Dr.K. Herzberg zum 70. Geburtstag gewidmet.
FrauI. Maurer und FräuleinI. Denker sei für ausgezeichnete technische Assistenz gedankt. 相似文献