Are there differences between the above listed technologies? Yes, there are, and there are vendors who offer ineffective devices to stroke survivors. Sometimes, these vendors base their claims on published clinical studies performed with EMG triggered NeuroMuscular Electrical Stimulators (EMG-triggered NMES), Electrical Stimulators (ES) or Functional Electrical Stimulators (FES). 

Electrical Muscle Stimulators (ES)

After a stroke many stroke survivors experience muscle dysfunction. Stroke rehabilitation and stroke treatment often includes electrical muscle stimulation to improve muscle performance. Since it is important to prevent muscle disuse electrical muscle stimulation will maintain mobility in the hope that the patient will regain spontaneously (some) muscle control. In case spasticity occurs (involuntary muscle contraction) electrical muscle stimulation may reduce the unwanted muscle contractions to obtain pain reduction (e.g. shoulder dislocation). Motion of joints may be lost (joint contracture) e.g. opening of hand, straightening of elbow or difficulty with shoulder movements. 

Use of electrical muscle stimulation includes early intervention and prevention of loss of motion. Benefit of electrical muscle stimulation in reduction of spasticity requires use for 1-2 hours per day over at least 1-3 months. If electrical muscle stimulation is discontinued spasticity is expected to return, requiring lifelong use. Properly working electrical muscle stimulation devices generate electrical stimulation impulses, which meet the specific requirements to obtain the optimal required muscle movements, like pulse form, pulse width, pulse repetition rate, stimulation frequency, stimulation current etc. etc. 

When electrical muscle stimulation is used in combination with a prosthetic application it is called Functional Electrical Stimulation (FES). Medications to paralyze muscles will reduce spasticity but result in weaker or completely paralyzed muscles. 

Transcutaneous Electrical Nerve Stimulators (TENS) 

TENS devices have been designed for pain reduction and nothing more! TENS decreases pain perception and may be used to control acute and chronic pain. Transcutaneous (through the skin) electrical nerve stimulation sends mild electrical pulses to specific nerves. The current generated might relieve stiffness, improve mobility, and relieve pain. The treatment is believed to stimulate the body's production of natural painkillers (endorphins). TENS devices are especially designed in such a way that they will not generate electrical currents causing muscle contractions and if they do, they might be even dangerous! All TENS devices are inherently unsuitable for any form of stroke rehab or stroke therapy. 

EMG triggered NeuroMuscular Electrical Stimulators (EMG-triggered NMES) 

EMG triggered NeuroMuscular Electrical Stimulation is a technology to detect the extremely small electrical ElectroMyoGraphic (EMG) signals still measurable in paralyzed muscles after stroke and use these signals to initiate electrical muscle stimulation impulses to those same muscles resulting in actual muscle movement. This form of stroke rehab is used to re-learn and re-develop spontaneous muscle control, which cannot be done by electrical muscle stimulation alone. 

Muscle movement is caused by electrical impulses originating in the brain, which are transmitted via nerve cells to the muscles. When a person wishes to initiate muscle movement the brain sends electrical signals to the muscles. Upon arrival of these signals, the muscles respond by contracting. These electrical signals can be measured over muscles and they are called ElectroMyoGraphic signals.

When brain damage is caused by a stroke, regular electrical impulses are not generated or can no longer reach muscles, normal muscle contraction becomes impossible. Although there are always minuscule EMG signals, these are mostly extremely small and unable to control the muscles. This often leads to irreversible damage and loss of muscle function, resulting in muscle paralysis such as "claw" hand or "drop foot". 

After a stroke, the stroke survivor is rehabilitated by physical therapy. This is done in the hope that there will be some form of spontaneous recovery and that the muscles will not become too stiff. In most cases however, recovery will not occur and stroke survivors will be left with severe disuse muscle atrophy and paralyzed muscles, greatly affecting their quality of life. 

Devastating paralysis of muscles can often be prevented if the stroke survivor is offered the possibility to re-learn the use of the affected muscles by improving electrical muscle activity. An excellent approach to re-educate muscles to achieve voluntary muscle contractions is to combine EMG measurement and NeuroMuscular Electrical Stimulation technologies as in the Biomove system. In almost all cases, there is still a very small amount of EMG activity, which reaches the muscles. These small EMG signals are picked up by "stick on" electrodes placed over the paralyzed muscles. The Biomove device then amplifies these small signals and when an internal preset "trigger" level is reached, the built-in electro stimulator returns an electrical stimulation impulse (NMES) to those same muscles. These muscles now respond as originally "instructed" by the patient's own brain signal. In this manner the patient is able to obtain direct muscle movement, assisted by the Biomove device. 

The stroke survivor uses this method of cognitive re-learning to rehabilitate the muscles of the otherwise paralyzed hand or foot. Training at home with the Biomove EMG triggered NeuroMuscular Electrical Stimulation device, may help achieve voluntary muscle contractions of the paralyzed muscles.

EMG triggered NMES, ES or TENS for Stroke Rehabilitation: What are the differences?