Impaired Ability to Suppress Excitability of Antagonist Motoneurons at Onset of Dorsiflexion in Adults with Cerebral Palsy

Figure 1

Experimental setup. Subjects were seated with their examined leg fastened to a stationary dynamometer. For experiment 1, subjects were instructed to dorsiflex their foot as fast as possible to 50% of MVC in response to an auditory cue. A window discriminator made it possible to time the tibial nerve stimulation to the onset of tibialis anterior (TA) EMG activity. This elicited an M-response (first grey shaded box) and an H-reflex (second grey shaded box) in the soleus (SOL) EMG. At least 45 trials, 15 tibial nerve stimulation and 30 no stimulation trials randomly interspersed, were obtained during dorsiflexion contraction. In experiment 2, subjects were asked to keep a steady dorsiflexion contraction at 10% of MVC for 2 min while given visual feedback of the target torque.