Figure 2.

Example of spastic cocontraction. The patient, in supine position with knee extended, is asked to produce an ankle dorsiflexion in the paretic side. Spastic cocontraction refers to inappropriate antagonist recruitment (ankle plantar flexors as GM and PL in this example) triggered by the volitional command on an agonist (ankle dorsal flexors as TA). The hypothesis is that a supraspinal factor (misdirected descending drive) is primarily involved and encounters an overall hyperexcitable ankle plantar flexor neuron pool. It takes some times for the patient to initiate dorsiflexor recruitment which is insufficient to counterbalance the ankle plantar flexor movement.