The Electrophysiology of Electrostimulation: A Technical Review

Physiologists in the science community have known since the 1800s that electrical currents exist in the human body, with the first publication of muscular and neural electrical activity occurring in the early 1900s. Eminent physiologists of the day quickly recognized that the nervous system used an activation signal containing units of electricity known as action potentials to control muscle exertion (Duchateau, 2011). These motor neuron-generated action potentials are disseminated to certain muscle fibers, collectively forming the motor unit, the final pathway the nervous system uses to send an electrical activation signal to the muscle — resulting in muscle contraction. Neuroscientifically, electrophysiology measures neural electrical currents and action potential activity. Read on to learn more about the electrophysiology of electrostimulation.

Motor Unit Physiology

Much is now known about how motor unit activity is organized during voluntary action performance.

• Motor units are engaged in a proportionately set order.
• Muscular force is controlled by simultaneous adjustments in the number of spikes during a set period and motor unit recruitment.
• Faster action potential generation leads to faster contractions.
• Peak discharge rates achieved during voluntary contractions are insufficient to produce maximum motor unit strength.
• Motor unit areas are reorganized as a person ages and due to certain neurological diseases; these conditions can also compromise motor unit activation.

If motor unit activation is compromised, studies support that it is possible to offset the deficit by using muscular electrostimulation to supplement activation.

What Is Electrostimulation?

Electrostimulation uses electrical stimulation to regulate the nervous system using neural signaling, enabling electrical and chemical functions that allow actional potential propagation, neurotransmitter release, and muscle activation. Specifically, electrostimulation imposes an external electrical current, generating action potential in muscle axons and inducing nervous system responses to elicit movement and impact sensorimotor function.

Electrostimulation can be used both diagnostically and therapeutically. The benefits experienced by individuals after several weeks of electrical stimulation suggest several physiological systems engage during this treatment (Ponce, 2014).

While applying an electrical current over muscles on a human being can allow contractile proteins to function, the activating signal is created in the axons of the inner muscle and not directly in the muscle fibers themselves. Similarly, most researchers have found that when currents are administered through externally placed electrodes, superficial muscle fibers are activated, but some findings suggest that stimulation on the skin’s surface can also engage the deeper parts of the muscle as well (Adams, 1985).

The Benefits of FES Therapy

Electrostimulation can be an invaluable therapeutic tool. One such clinical application is functional electrical stimulation (FES) therapy, which utilizes electrostimulation to send computer-generated electrical signals in sequential order to the body’s paralyzed or weakened muscles to allow their contraction and functional movement.

In addition to its potential to decrease pain, fatigue, and spasticity while preventing muscular atrophy, improving cycling endurance, and enhancing exercise tolerance, research has shown that FES therapy can also:

• Decrease seat pressure and prevent the formation of pressure ulcers (Dolbow, 2013).
• Improve body composition, leading to healthier ratios of lean and fat mass as well as increased bone mineral density (Dolbow, 2014).
• Preserve or improve neurological function for patients with MS when incorporated into activity-based rehabilitation (Hammond, 2015).
• Improve muscle health in non-ambulatory people with MS (Reynolds, 2015).
• Promote physical and functional recovery in chronic SCI, increase muscle size and force generation potential, reduce spasticity, and improve quality of life (Sadowsky, 2013).
• Provide functional improvements in the late period of SCI (Yasar, 2015).

Unlock the Power of Electrostimulation Through FES Cycling and the MyoCycle

FES cycling therapy uses electrostimulation to allow weakened or paralyzed muscles to enjoy movement and exercise once again, leading to countless benefits supported by emerging research from recent years.

If you are ready to learn more about the MyoCycle Pro, our FES bicycle designed specifically for clinical use, contact us. At MYOLYN, we are passionate about educating our customers on the latest research outlining the benefits of FES therapy for people with paralysis and providing exercise tools that can be used in clinical settings or at home to improve lives.