Proceedings of The Physiological Society
University College London December 2005 (2006) Proc Physiol Soc 1, PC18
Corticospinal excitability changes following functional electrical stimulation of the tibialis anterior muscle in healthy humans
Kypriglis-Kypriotis, Konstantinos; Tsiringakis, George; Lampropoulou, Sofia; Nowicky, A V;
1. School of Health Sciences, Brunel University, Isleworth, London, United Kingdom.
Studies have demonstrated that functional electrical stimulation (FES) is effective in rehabilitation . FES, as well as repeated voluntary activity, has been shown to produce long lasting changes in sensorimotor excitability . FES has been used for the rehabilitation of foot drop, following stroke. However, there is limited evidence comparing the effects of FES with voluntary activation of ankle dorsiflexion in healthy participants. We have used transcranial magnetic stimulation (TMS), to compare changes produced by repetitive FES to that of simple repetitive voluntary dorsiflexion. Seven healthy volunteers received both treatments in random order: an FES and a voluntary activation session separated by at least 1 week. The voluntary exercise consisted of 30 min of repetitive dorsiflexion producing 30% of maximum voluntary torque. Strain gauge measuring the torque of ankle dorsiflexion was used to provide visual feedback and ensure that similar sustained (3 s) contractions were maintained at 11 times a minute. Using an FES device (Odstock stimulator, 04CHS, Salisbury District Hospital, Wiltshire) electrical stimulation was applied to the tibial nerve through a pair of circular electrode pads (3.8 cm) for activation of the tibialis anterior (TA) muscle, a prime ankle dorsiflexor. Automatic repetitive stimulation trains (25 Hz, 3.5 s duration, at 11 times per minute) was applied for 30 min. Similar levels of FES induced torque matching the 30% of maximum level of voluntary activation was achieved by adjusting the stimulus current. Motor-evoked potentials (MEPs) were monitored by surface electromyography of the right TA in relaxed subjects placed in a semi-reclined position. TMS was applied using a 70 mm figure-of-eight coil (rapid MagStim, in single pulse mode) over the left motor cortex (intensity 1.2 times resting motor threshold). MEPs were measured for 15 min before and for 60 min after completion of exercise. There was a significant increase in the averaged MEPs for both interventions, which were still significant at post 60 min (95
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