Parameter Changes in Functional Electrical Stimulation

This study aims to look at how changes to a person's functional electrical stimulation might change how they walk. Functional electrical stimulation (FES) is commonly used to help people with foot drop from upper motor neurone conditions such as stroke or multiple sclerosis. This group of people have muscle weakness which makes it difficult to lift the foot, which causes trips and falls.

FES reduces foot drop by using a portable device to apply short electrical pulses to the nerve which lifts the foot. The FES device stimulates this nerve only during the swing phase, when the foot is off the floor. Typically this is achieved by using a foot-switch, which detects when the heel leaves the floor. Stimulation begins a short interval of time after the heel leaves the floor, ramps up from zero to set stimulation for the individual, and at another period of time after the heel hits the floor, stimulation ramps down from set amount to zero. There are four time intervals described here which can be varied by the clinician on the device:-

• Delay (the time between heel lift and the start of stimulation)
• Ramp up (the time for stimulation to reach full strength)
• Extension (the time between heel strike and the ramp down)
• Ramp down (the time for stimulation to reach zero from full strength) These intervals are usually set by experienced clinicians using a qualitative assessment of the patient's walking and trial-and-error. A literature review has found no published studies which compare walking with different timing. This knowledge would be useful for clinicians, who could use this information as a starting point in finding the best timing parameters for each patient.