Functional Electrical Stimulation (FES)
Also known as FNS (Functional Neuromuscular Stimulation) or
Computerized Functional Electrical Stimulation (CFES). This system controls the stimulation parameters by a         computer. Often used to describe FES cycling systems.

RESEARCH RESULTS OF FES THERAPY

FES WILL HELP TO RESTORE THE NORMAL CYCLIC ACTIVITY OF THE CONTRACTION AND RELAXATION PHASES OF A HEALTHY MUSCLE

Healthy muscle function is basically a cyclic response with equal moments of contraction and relaxation. When a muscle is not functioning properly, one of these responses is typically absent or shortened. After an injury, muscle tissue will “splinter”. In this condition, the muscle fibers are held in a firm, contracted state to protect the muscle from being over used and causing further injury. This condition is the “knot” that is felt when an injured muscle is palpated. The goal of FES is to replicate the body’s own natural functions. FES will restart the cyclic activity of the contraction and relaxation phases to return the muscle to a more normal functioning pattern.

FES WILL REDUCE INFLAMMATION THROUGH PRODUCTION OF MUSCLE CONTRACTIONS

The prolonged contraction of a splinted muscle is initially useful but this immobilization of the muscle quickly leads to a reduction in circulation and an increase in inflammation. Inflammation is a natural response of the body to injury. However, if the swelling associated with the inflammation lingers, there can be many detrimental results. The inflammation reduces the ability of the body to remove the diseased tissue from the injury. In addition, inflammation does not allow the cellular components for regeneration to reach the injury site. Without the components needed for repair, the tissue cannot regenerate to its functionally equivalent preinjury state.

FES WILL PRODUCE MUSCLE MOVEMENT TO REDUCE ADHESIONS DURING HEALING

Adhesions will form at the site of an injury to immobilize the tissue, therefore protecting it from further injury. However, immobilization for an extended period of time is one of the factors leading to a preponderance of non-functional adhesions. Movement of the injured tissue results in the condition necessary for the production of more organized functional tissue, therefore the possibility of a full recovery is greatly increased.

TREATMENT OF DEEP MUSCLE PROBLEMS INCLUDING SPINAL AND PELVIC ISSUES

One of the specific reasons that FES is beneficial to the equine practitioner is due to the depth of penetration of the signal. The FES signal can reach 3 to 4 inches below the surface of the skin so that the deep muscle, tendon and ligament tissues of the horse can be stimulated. This is of great value when dealing with spinal and pelvic problems. In addition, the FES signal feels comfortable, so the horse remains compliant to the treatments without the need of a tranquilizer. A successful case study is documented on this site.

TREATMENT OF DEEP DIGITAL FLEXOR TENDON
TREATMENT OF SUPERFICIAL TENDONS AND LIGAMENTS

Due to the depth of penetration, FES can be used for rehabilitation of the deep digital flexor tendon. A case study listed on the website outlines the successful progress of a deep digital tendon rehabilitation.

Tendon and ligament rehabilitation has been studied extensively in humans. The evidence is strong that during both tendon and ligament rehabilitation, tension due to muscle movement will assist in the repair of the injury, leading to a return of more normal function (Mass et al, 1993).

Synder-Mackler L, et al (1995) found that using electrical stimulation early in the rehabilitation process of anterior cruciate ligament reconstruction improved the functional ability of the knee when compared to the controls that received no electrical stimulation. In addition, the maintenance of muscle strength during the rehabilitation process was significantly better with the electrical stimulation than with the control.

PREVENTION OF TENDON AND LIGAMENT PROBLEMS

Stiffness or injury to the tendon at the insertion or attachment point can cause discomfort and poor quality movement. Tightness in the ligaments is also a common problem leading to injury and pain. FES can mobilize the tendons and associated ligaments to help in rehabilitation or improve the quality of movement.

Fatigue is the precursor to injury and reduction in fatigue can lead to fewer injuries. FES has been successfully used as a prophylactic, reducing muscle, tendon and ligament strain therefore avoiding potential injury.

Svantesson et al (1998, 2000) found that fatigue develops earlier in subjects that had increased stiffness in the tendons. Therefore, the use of FES to loosen tight tendons can appreciably decrease fatigue leading to less chance of failure of the tendon.

IMPROVED PERFORMANCE DUE TO IMPROVED MUSCLE FUNCTION

Pain after an injury or surgery causes the patient to have difficulty in contracting and relaxing the effected muscles. As a result of the limited use, there can be a lack of sensory input from the muscle. This lack of input makes movement more difficult, and any movement that is performed is uncoordinated. When the muscle is stimulated by FES to encourage the contraction/relaxation cycle to return to normal, there is an associated increase in the sensory input from the muscle. This input is necessary for muscle coordination and performance.

FASTER RECOVERY AFTER INJURY OR SURGERY

In rehabilitation, the typical exercise program used after injury or surgery involves low stress to the muscles and joints, and therefore the fast-twitch type fibers would rarely be recruited. With electrical stimulation, these fast- twitch fibers can be recruited at higher intensities. Therefore, faster and greater strength gains can be made with the use of electrical stimulation during rehabilitation (Andrews et al, 1998).

REDUCED DISCOMFORT FROM ARTHRITIC CONDITIONS

Arthritic pain from joint problems produces poor quality asymmetrical muscle movement. Therefore, arthritis results in not only joint pain, but also secondary muscular pain. In addition, many arthritic conditions may originate due to the uneven pressures on the joint because of asymmetrical muscle development and use. In both of these situations, FES can assist in reducing the muscular discomfort or the pressure on the joint due to asymmetrical muscle use.

Research has found that children with juvenile chronic arthritis have reduced muscle strength and thickness in the muscles near the inflamed joint (Lindehammar and Backman, 1995). Therefore, depending on the severity of the case, the use of FES to improve muscle integrity could help in reducing the discomfort associated with arthritic conditions. A successful case study is documented on this site.

GENERAL CONSIDERATIONS OF FES THERAPY

FES is a rehabilitation technique where electrical current is applied to enhance a missing or impaired neurological function. FES replicates the body’s electrical impulse from the brain and results in a response so similar to the body’s actual activity it is referred to as a “functional” response. Therefore, the name Functional Electrical Stimulation (FES) was given to this type of electrical muscle stimulation. For example, the application of FES to the appropriate muscles of the hand can produce a movement so precise that a gripping action can be achieved.

FES can be used to improve both sensory (nerve) and motor (muscular) function. For FES to be effective, the lower neurons must be intact from the anterior horns of the spinal cord to the neuromuscular junction of the muscle.

In humans, FES is used extensively in situations where lower motor neurons are intact and muscle tissue is healthy, such as in:

• spinal cord injury
• stroke
• head injuries
• cerebral palsy
• multiple sclerosis

FES is not used when there is lower motor neuron damage, such as in:

• polio
• amyotrophic lateral sclerosis (ALS)
• peripheral nerve injuries
• muscular dystrophies due to unhealthy muscle tissue

The stimulation of motor nerves cannot occur by a steady flow of direct stimulation, therefore a pulsed current must be used. Therapeutic electrical stimulation is applied through the use of surface electrodes.

The three main purposes of FES are:

1. To restore skeleto-motor functions
2. To restore autonomic functions
3. To restore sensory functions

FES produces contractions in muscles and tendons as well as in the ligaments associated with the joints being stimulated. Some movement to the ligament may be possible due to the application of FES, as a secondary result of the muscle and tendon movement. However, this movement will not be as influential as with muscle and tendon tissue due to the lack of an action potential in the ligament. FES muscle stimulation, which results in a contraction, is physiologically identical to the one produced by the functional nerve. In addition, FES can provide restoration of a lost motor function through the stimulation of the intact motor neurons. This is why FES has been used extensively in the rehabilitation of spinal cord injury patients.

Amplitude and pulse width are varied to control the contraction for the patient's needs. Closed loop systems, in which the stimulation is moderated automatically according to parameters such as joint angles and foot pressure distribution, are now being developed, but few of these are in routine clinical practice.

During electrical stimulation recruitment of muscle fibers occurs in the opposite order of normal recruitment with the large diameter fibers being activated before the smaller diameter fibers. This is probably due to the fact that large diameter fibers are stimulated with lower voltage because of the wider spacing between nodes. In addition, the fibers closest to the electrodes will fire first. Recruitment continues to a point where no more increase in force can be obtained and at this point the muscle is considered “saturated”.

Indications/Contraindications