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George E. Carvell, PhD, PT   University of Pittsburgh
PD MOTOR DEFICITS: What It Teaches Us About Movement II
Individuals with Parkinsonís Disease tend to move slowly (bradykinesia). The level of force production by PD patients is often comparable to aged-matched controls. However, force curves show that movement time is increased for PD subjects compared to neurologically-intact elderly. Rise and fall times to and from peak torque are slower than normal (see fig 18-5). Part of this slowing may be due to a motor control problem and part may be due to the increased stiffness (rigidity) characteristic of PD. Reaction times are also prolonged (not shown here).
Fig 18-5 In: C.M. Fredericks and L.K. Saladin, Pathophysiology of the Motor Systems. Philadelphia: F. A. Davis, 1996.
Fig 18-5 p 430
Can individuals with PD move fast? An experiment by Hallett and colleagues looked at EMG from elbow flexors and extensors while an individual performed rapid movements. The authors concluded that PD does not prevent the normal triphasic EMG pattern characteristic of fast movements, but a single triphasic burst is inadequate to achieve the desired ROM. Therefore, the PD subjects repeated the triphasic pattern in an attempt to reach the final desired position which they overshot (see fig 14.11 in Brooks).
Brooks Fig 14.11
P 307