Motor control (Hagbarth, Axelsson): For many years research was focused on
spinal reflexes and control mechanisms important for normal movement. These
control mechanisms may be disturbed in patients with different types of movement
disorders. Of special interest was research amied at defining the function
of muscle spindles and the fusimotor system. In later years the project have
been concentrated on investigating the mechanisms of muscle thixotropy. Thixotropy
means ”changed by touch”. A thixotropic substance acts like a
semisolid gel but becomes more fluid and compliant when mechanically disturbed.
It returns to its previous more solid state after a certain time of rest.
Human skeletal muscles posseses thixotropic properties. The stiffness or mechanical
resistance of both intra- and extrafusal muscle fibres is depending on the
immediate preceding mechanical history of the muscle. Studies have shown that
the motor control system must adjust for thixotropy dependant changes in extrafusal