In complex biological systems, like a humans, electrical and chemical communications occur through synaptic transmission in which neurons (the morpho-functional unit of the nervous system) exchange information to elicit an excitatory or inhibitory response. With the term neuromodulation, we refer to a process which is able to cause the “alteration of neuronal and synaptic properties by neurons or substances released by neurons” (Katz and Calin-Jageman, 2009).

However, neuromodulation is a term that describes both a biological/physiological process as well as a “therapeutic” approach.

In biology, classic synaptic transmission involves the secretion of neurotransmitters by a neuron (specifically his axon) aiming to target specific receptors of another neuron.

 

Neuromodulation, however, is a different process in which neurotransmitters (or neuromodulators) are being able to modulate different types of neurons by targeting different receptors (G-protein coupled receptors): neuromodulation, in fact, can “modify neural circuit output to produce extensive adaptability in behaviours” (Nadim and Bucher, 2014).

The conceptual framework of neuromodulation as a therapeutic approach is similar to the physiological process as the main outcome is the alteration and modulation (i.e. normalization) of the nervous system function to elicit a behavioural adaptation response.

Neuromodulation as a therapy has different forms, methods and treatment modalities: it can be administered both by targeting specific sites through an artificial external stimulus (Electrical Muscle Stimulation, TENS, Spinal Cord Stimulation, Cortical Stimulation etc.)   as well as stimulating the learning process and plasticity function through feedback mechanisms (neurofeedback).

Neurofeedback, as an example, has been widely used for many years in the treatment of various conditions such as ADHD (Arns et al, 2009) as well as in the improvement of sports performance (Graczyk et al, 2014).

Even the use of prosthetics, which are devices aimed to replace and/or improve an impaired motor/sensory function, has led the way in recent years into the growing success of the replacement of impaired neural functions (Luan, Williams, Nikolic and Constandinou, 2014).      

But one of the most important and widely studied neuromodulation approaches is the one using electrical current both to modulate pain sensation by targeting afferent sensory nerves (TENS) as well as to elicit a neuromuscular response by targeting efferent motor nerves (EMS).

Starting from the early 60s, neuromodulation as a treatment has evolved constantly from deep brain stimulation and spinal cord stimulation up to the more recent motor cortex stimulation and functional electrical stimulation (FES) and the exciting human-brain interface systems.

In regards to sports performance, it has been only with the start of electrical muscle stimulation (EMS) application as a form of training, rather than therapy, that a conceptual breakdown has arisen in the world of physical preparation.

Thanks to the intuition and practical application of some smart and innovative coaches and trainers between the 80s and 90s, the use of EMS to improve strength and physical conditioning has opened a new window into the understanding of how the nervous system adapts to stimuli.

In the next article we will explore The Four Main Aspects of EMS Training Design.