Article

The specific neuromuscular mechanisms for compromised muscle strength with PD,
and the improvement that occurs with medication, have not been clearly
delineated. This study assessed knee extension and flexion strength of PD
patients whilst on and off medication and examined the neural mechanisms
responsible for any changes. Ten idiopathic PD patients were assessed whilst on
and off medication (>/= 12-h after drug withdrawal), approximately 7 days apart.
Isometric strength of the knee extensors and flexors was assessed, and the
interpolated twitch technique used to measure activation of the knee extensors.
Surface EMG was also used to measure neural drive to the agonists and
antagonists. Without medication isometric strength of the knee extensors (7%) and
flexors (11%) was impaired and the interpolated twitch technique revealed
activation of the knee extensors was reduced (8%, P=0.005). Maximum agonist
amplitudes for nkee extension and flexion were unchanged off-medication (0.59 P<
0.77). The agonist and antagonist EMG-force relationships, and the maximum
antagonist EMG, were unaffected by medication withdrawal. The decrease in knee
extension strength when PD patients were off medication was due to reduced
activation of the agonist muscle, rather than any change in antagonist
co-activation, and these changes were associated with reduced locomotory
performance.

Langue : ANGLAIS