What is FES? 1) In this section, we are going to introduce Functional Electrical Stimulation or FES as it is often known. Although FES has been around for a long time it is only just becoming widely accepted as the powerful tool it actually is. I first worked with FES in the 1970’s which is, by any one’s standards, a long time ago now. The technology available in those days was not so easy to use compared with the systems we have available today. Many technologies seem to come in and out of fashion for a variety of reasons. With FES, I feel that the growth in popularity is in part due to the increased sophistication of the technology today. Modern systems offer fine control of the stimulation and as a result produce a more predictable result. 2) Whatever era we are in the fundamental questions of interest remain the same? • • • • •
What can FES do that is worth the trouble? How does FES work? Is it safe to use? Will it damage healthy nerves and muscles? Can the central nervous system or a lower-motor neuron system be retrained or reorganised through FES? How can we design FES systems for maximum benefi
During this course we will touch on many of these questions. 3) It was just prior to 1800 that Galvani discovered that electricity applied to the sciatic nerve of a frog would produce a contraction of the frog’s leg. These foundations and the controversy between Galvani and a scientist called Volta laid the foundations for FES. Volta, was a professor of experimental physics and he was among the first to repeat Galvani’s experiments. At first, he embraced the idea of “animal electricity”. However, Volta came to believe that the contractions depended on the metal cable Galvani had used to connect the nerves and muscles in his experiments. Galvani believed that the animal electricity came from the muscle in the frogs pelvis. Volta, in opposition, reasoned that the animal electricity was a physical phenomenon caused by rubbing frog skin and not a metallic electricity.
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In fact every cell has a cell potential. Biological electricity has the same chemical underpinnings as the current between electrochemical cells, and thus can be duplicated outside the body. Volta's intuition was correct. Volta, essentially, objected to Galvani’s conclusions about "animal electric fluid", but the two scientists disagreed respectfully and Volta coined the term "Galvanism" for a direct current of electricity produced by chemical action. We can say that owing to an argument between the two in regard to the cause of the electricity, Volta built the first battery in order to specifically disprove his associate's theory. Volta's “pile” became known as a voltaic pile. 4) As we move further into the 1800’s there was a growing scientific interest in Galvanism. Let me tell you a story… The inside of the Glasgow University Anatomy theatre was crowded. After all, it wasn’t everyday that anatomists worked on a fresh corpse in full public view. Five minutes before Matthew Clydesdale’s corpse was brought from the gallows, Dr. Andrew Ure charged his galvanic battery. A series of experiments were then carried out on the recently hanged body. 5) The final experiment had spectators believing that Clydesdale had returned from the dead. Once the current was turned on, Clydesdale began to raise his hand and point to the people in the audience. ‘…At this spectacle several spectators were forced to leave the arena from terror or sickness, and one gentleman fainted’. For more than 200 years we have known that electricity applied to the body can cause contraction of muscle. Over the last 50 years our understanding has improved and with it so has the technology to make FES one of the most powerful and flexible tools for rehabilitation. 6) In the 19th Century there was significant interest in electrotherapy. An electric bath was a medical treatment in which high-voltage electrical apparatus was used for electrifying patients by causing an electric charge to build up on their bodies.
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In the USA this process was known as Franklinization after Benjamin Franklin. The process became widely known after Franklin described it in the mid-18th century, but after that it was mostly practiced by quacks. Golding Bird brought it into the mainstream at Guy's Hospital in the mid-19th century and it fell into disuse in the early 20th century. These days we have less ambitious expectations for electrotherapy. Let’s start our explorations of modern FES 7) Here is our definition - FES is a therapy method where nerves are stimulated through the skin with precisely controlled electrical energy in order to cause a functionally useful muscular contraction. 8) You may have come across something called Motor Stimulation which is a more general definition. Motor stimulation is defined as producing a muscle contraction by the use of electrical stimulation. This can be stimulation via the motor nerves as with FES or if the muscle is denervated, via direct stimulation of muscle fibres. We will be looking at electrotherapy of denervated muscles in a separate course. 9) FES and Motor Stimulation are often described as forms of electrotherapy. In fact there are many forms of electrotherapy. Some are not widely seen in the UK and we won’t be covering them in this particular course. Our intention is to focus on FES with the RehaMove system. 10) With the RehaMove system we will be placing electrodes on specific muscles and using the software within the product to deliver precise electrical energy to the body. Generally we are using larger muscle groups for FES Cycling. We don’t need to worry at the moment about the placement of electrodes - we will return to this later. We just need to recognise that the electrical energy that flows into the muscles and nerves via the electrodes can generate useful muscle contractions. 11) Each muscle has a nerve architecture including many of what are called Motor Units. These motor units supply, sometimes a few and sometimes many, muscle fibres. This depends on the particular muscle.
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12) High force, postural muscles have many muscle fibres and “low force”, precise control muscles, contain relatively few muscle fibres. The important take away at this point is that all muscles are not the same. 13) With FES Cycling we will be looking for a training effect. We will have to think about which muscles we need to train and we must think about what outcomes we want. We know that electrical stimulation can produce the necessary muscle contractions to pedal a bike but somehow the muscles need to produce these contractions at the right time. The software and hardware we use in FES cycling is designed to precisely control when particular muscles are stimulated. We are also going to learn how three things influence how strongly a muscle will contract due to FES. These things are the so called Frequency, Current and Pulse Width. We will be reviewing the importance of these so called stimulation parameters shortly. 14) The RehaMove cycling programmes are designed to synchronise the stimulation delivered to the major muscles with the movement of the bike’s pedals. The quadriceps and other muscle groups are effectively turned on and off at the necessary times during each revolution of the bike pedals. 15) The stimulator and the bike talk to each other during an exercise session and data is passed back and forward. The stimulator needs to know the position of the pedals at all times so that it knows which muscles need to be active at any time. As the pedal speed increases, the software will automatically adjust the stimulation to suit. Of course the stimulator software is watching for error situations which might indicate a problem such as an electrode becoming detached or when the pedals stop moving suddenly due to a leg spasm. Ok that concludes our introduction. See you in the next session.
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Derek Jones