Acute Effects of Wearable Electrical Stimulation in Stroke

Spasticity is one of the most significant motor impairments limiting functional capacity in stroke, occurring in approximately 20-30% of all stroke survivors. According to current approaches, spasticity is defined as a motor disorder characterized by a velocity- and muscle length-dependent increase in resistance to passive muscle stretch, resulting from hyperexcitable descending brainstem excitatory pathways and accompanying exaggerated stretch reflex responses. Post-stroke spasticity is often associated with pain, soft tissue stiffness, and joint contractures, which can lead to abnormal extremity posture, decreased quality of life, and increased treatment costs and caregiver burden. Early detection and management of post-stroke spasticity can not only reduce these complications but also improve function and increase independence.

In clinical practice, medical (local and general muscle relaxants, Botulinum Toxin A), surgical, and physiotherapy approaches are utilized for spasticity inhibition and modulation. Electrical stimulation has been applied for many years in various forms to manage spasticity. Surface electrical stimulation is a non-invasive therapeutic method used to increase muscle strength and passive range of motion, as well as to improve voluntary motor control by reducing pain and spasticity in patients with central nervous system involvement. However, optimal parameters for reducing spasticity remain a subject of debate in the literature. While conventional protocols often use high-frequency settings (2-100 Hz), studies also show low frequencies can be effective. Furthermore, the integration of electrical stimulation with wearable technologies has moved these applications beyond traditional clinical settings, providing ease of use, continuity, and personalized, targeted intervention options.

The EXOPULSE Mollii method (EXONEURAL NETWORK AB, Danderyd, Sweden) is an innovative approach for non-invasive, self-administered electrical stimulation utilizing multiple electrodes incorporated into a full-body suit. It is specifically designed to reduce spasticity and improve motor function in neurological disorders. The method's primary mechanism is based on reciprocal inhibition, which occurs by stimulating the antagonist of a spastic muscle at low frequencies and intensities. It is hypothesized that this stimulation reduces spasticity in the agonist muscle (e.g., elbow flexor) by stimulating the afferent nerve fibers of the antagonist muscle (e.g., elbow extensor), activating inhibitory Ia interneurons in the spinal cord, and thereby decreasing the excitability of the agonist motor neuron.

Additionally, similar to transcutaneous electrical nerve stimulation (TENS), the suit may induce neuroplastic changes in brain or spinal cord circuits. It is postulated that spasticity reduction is mediated by the activation of large-diameter sensory nerve afferents that modulate abnormal interneuron activities across several spinal segments. The suit utilizes 58 dry, embedded silicone electrodes, operating with a square wave pulse shape, a pulse width between 25-175 microseconds, and a constant current at a frequency of 20 Hertz.

Previous pilot studies evaluating the EXOPULSE Mollii method in patients with stroke or cerebral palsy have shown potential benefits. However, gaps remain in the literature due to the lack of control groups, absence of acute effect studies, and methodological variations. Therefore, the objective of this clinically controlled study is to investigate the acute effects of the EXOPULSE Mollii Suit on spasticity severity, pain, fatigue, upper and lower extremity functions, balance, gait, endurance, and hand functions in individuals with stroke. This is a clinically controlled trial. Individuals diagnosed with stroke will be assigned to either the treatment group or the control group.

Intervention Group: Participants will receive electrical stimulation via the EXOPULSE Mollii Suit for a single 1-hour session. The stimulation will be applied at a prescribed, therapeutic intensity through the embedded silicone electrodes based on the participant's specific functional impairments.

Control Group: Participants will wear the same EXOPULSE Mollii Suit for 1 hour; however, they will receive only minimal-intensity electrical stimulation restricted strictly to the neck and unaffected (non-paretic) extremities.

To evaluate the acute effects, all clinical assessments will be performed by a blinded researcher at two specific time points: immediately before donning the suit (baseline) and immediately after the 1-hour application.

The evaluation parameters will include:

• Spasticity severity of upper and lower extremity muscles via the Modified Ashworth Scale (MAS), recorded via the Mollii Suit computer interface.
• Pain, fatigue, and satisfaction levels using the Visual Analog Scale (VAS).
• Hand performance using the 9-Hole Peg Test.
• Functional capacity using the Stroke Rehabilitation Assessment of Movement (STREAM) scale.
• Lower extremity functional level using the 5 Times Sit-to-Stand Test.
• Functional mobility skills using the Timed Up and Go (TUG) Test.
• Gait performance using the 10-Meter Walk Test.