ETS – biofeedback-controlled stimulation

Meaning of ETS

The acronym comes from the English phrase “EMG Triggered Stimulation.” In Hungarian it could be translated as EMG-triggered stimulation, but I prefer the phrasing biofeedback controlled stimulation.

EMG is also an abbreviation: Electromyogram, i.e., the recording of the muscle's electrical activity. It's just like recording an EKG from the heart, which captures the electrical signals generated during heart muscle contraction. The difference is that an EMG is recorded from a muscle rather than the heart.

"Triggered" means caused by some phenomenon. For example, if you nudge a glass, its water may spill. The “trigger” is the clumsy movement that has a consequence, e.g., the contents of the glass pour out.

In this context, stimulation refers to muscle contraction induced by electrical impulses. With an appropriate electrical impulse, even a paralyzed muscle can be made to contract. The effects vary depending on the impulse settings, such as regaining muscle strength, reducing spasticity, preventing muscle atrophy, retraining the muscle–brain connection, and so on.

Application of ETS

When using ETS, the device monitors the electrical activity (EMG) of the target muscle. An electrical potential is generated during muscle contraction. The more muscle fibers activated, the greater the signal. A threshold value can be set on the device. If the muscle activity reaches that level, the device delivers the preconfigured electrical stimulation impulse to the muscle, i.e., it "boosts" the contraction.

Its main application is the rehabilitation of central paralysis. It is recommended to use ETS at a stage of recovery when at least a minimal amount of the movement lost after paralysis has returned. The ETS device helps by amplifying the patient's weak and coarse movement attempts, making them more effective. Its primary role is to retrain the functioning muscle–nerve connection.

EMG is sensitive, so it detects even very weak electrical signs of muscle activation. For example, an attempt to move a paralyzed arm may not produce visible movement, but the device senses the faint attempt. It then provides feedback and an assistive stimulation. This is very beneficial for the muscle and the nerve, and even more so for the patient's motivation. The device indicates that the intention is present and that with persistent practice control can be partially or almost fully restored.

After a stroke, paralysis often persists because the patient is not sufficiently motivated to exercise. Primarily, this is because attempts to move the paralyzed hand yield little result. One would need to practice for many months despite only minimal movement. Most people give up and thus abandon the possibility of improvement.

Using ETS does not guarantee success, but it creates the possibility. Even with ETS, persistent practice supports the brain–nerve "rewiring," but the results achieved with ETS can be orders of magnitude better.

One of its main uses is treating incontinence, where it is combined with pelvic floor exercises. The device detects voluntary contraction of the pelvic floor muscles and triggers the assistive stimulation, which often multiplies the effectiveness of pelvic floor training.

Brain plasticity

Plasticity is the brain's ability to undergo anatomical and functional change. Throughout life the brain continuously alters its physical structure and reshapes its "circuits." This malleability is ensured by the formation of new connection points (synapses) and the rearrangement of existing neural connections, which are the physiological basis of learning. After brain injury, the brain is even capable of growing new axons! If certain brain areas "fail," other parts can take over their tasks.

Plasticity is therefore the brain's adaptability to changing environmental conditions.

Thus the brain's plasticity (its self-reforming and learning ability) makes it possible, for example, for another brain area to take over the function of a motor area destroyed by a stroke. A stroke can be imagined as the tearing away of the motor nerve roots running from the brain to the muscle, resulting in loss of connection. During recovery, relearning movement means the "rewiring" of motor nerves: the motor nerve connects to a new brain area, and with persistent practice movement can be relearned. Movement precision is usually less than the original, but with the newly learned function quality of life and independence can be restored.

The ETS technique is currently the most modern home-usable method for learning a new movement to replace lost movement after paralysis. Case reports suggest that new abilities can even be developed years after a stroke.

In this video I present the DuoBravo ETS device, which in Germany is one of the basic devices used for stroke rehabilitation. There it is prescribed for people who have had a stroke. At home the patient must purchase it at their own expense, which can be done by clicking here.