Muscle, reflex and central components in the control of the ankle joint in healthy and spastic man.

摘要: In understanding the control of ankle joint during different motor tasks, we have to investigate at least three components, namely influence i) passive and intrinsic properties intact active muscle system around (termed non-reflex component), ii) mechanical importance stretch reflex in stretched unloaded muscles, iii) supraspinal reflex. This thesis is dealing with components healthy spastic persons sitting, standing, walking. The results are based on H-reflex measurements from extensor muscles. During experiments foot was mounted a platform (portable walking) which torque position were measured. To elicit reflex, rotated by strong connected platform. investigated measuring changes torque. Electrically, recorded as compound action potential through bipolar surface EMG electrodes placed over soleus muscle. experiments, tibial nerve stimulated popliteal fossa experiments. how contractile humans depend history activation, stiffness extensors subjects. At matched background contraction sitting subjects, prolonged increased 49%. Muscle yielding has been considered especially important for compensation. We found general lack yield mechanically showing that prominent factor normal movements joint. both persons, isometric, contracted muscles sitting. posed question; regulated more functional tasks. dealt studying isometric ramp contractions walking persons. subjects modulated consistency task dependent control. patients lacked modulation. earlier findings it suggested decreased modulation could caused pre-synaptic inhibition Ia terminals or change recruitment gain. test if behaved H-reflex, short latency Here strongly step seen but when comparing excitation levels (same EMGs) standing walking, no task-specific except one relating level. Therefore, emphasise not always possible draw conclusions about observations H-reflex. When investigating patients, impaired extent demonstrated same time patients. levels, responses compared before after reversible block common peroneal an attempted, voluntary, fictive dorsiflexion block. (ABSTRACT TRUNCATED)