Know-How
From Experiment to Evidence: Whole-Body EMS-Training
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Electromyostimulation (EMS) uses electrical impulses to achieve targeted muscle contraction. From its historical use by Luigi Galvani to modern whole-body EMS, the method combines science and efficiency. It enables intensive, time-saving training by activating all major muscle groups and is used in both competitive sports and rehabilitation.
Electrical stimulation of the musculature leads to an involuntary contraction of the activated muscle fibres. Luigi Galvani already recognised this connection in the 18th century in his early experiments on frog legs. Among other things, he used the electricity from lightning strikes to cause the frog's muscles to contract (Bresadola, 1998). He connected the nerve fibres of the frog's legs to a kind of lightning conductor. Fortunately, today's form of EMS training no longer relies on the electric arcs between clouds and the earth, which have an electrical energy of several billion joules.
The first mechanical power generators designed in the 19th century to control local muscle areas are still used today as a model for modern electrostimulation. After the turn of the century, renowned researchers established the basic laws of electrostimulation with their studies on the effect on the nervous and muscular system and the definition of a terminology for electrostimulation.
Effectiveness based on physiological muscle contraction
The striated skeletal musculature ensures the supportive and targeted motor skills of humans. In contrast to smooth muscles, their contraction occurs arbitrarily via a cerebrospinal nerve impulse. This is transmitted as an action potential from the central nervous system via the spinal cord and nerve fibres to the α-motoneurons. The action potential triggers the release of the neurotransmitter acetylcholine at the motor end plates of the muscle fibres belonging to the respective α-motor neuron (motor unit). Acetylcholine binds to its receptors on the postsynaptic membrane and leads to the opening of voltage-dependent calcium channels via an end plate/action potential, thus triggering the contraction. The contraction occurs through the interaction of the myofilaments actin and myosin, which, by ‘sliding past’ each other, cause a shortening of the sarcomeres (the smallest contractile unit of the muscle) and, in the overall process, a muscle contraction [1, 2].
Whole-body electromyostimulation (EMS) is also based on triggering muscle contraction via an electrical impulse. This impulse is transmitted externally via electrodes attached to the trunk and proximal extremities. The electrical impulses emitted are low-frequency (usually 85 Hz), trigger a brief muscle twitch and, through repeated delivery of the electrical impulses, lead to a contraction of the affected muscle [3]. EMS training is customised for each individual and carried out in a 20-minute session once a week (maximum every 4 days) under personal supervision (1:1, maximum 1:2). At the beginning of the application, the individual intensity tolerance of the pulse strength must be identified and gradually approached.
The modern form of electrotherapy
Electromyostimulation has been used for many years in training and competitive sports, as well as locally in rehabilitative and physical therapy. In contrast to local application, in which the coordinative stimulus is missing and the trained strength can only be implemented with difficulty in everyday life, whole-body EMS training combines externally triggered muscle contraction with voluntary muscle contractions. The additional exercises can be performed isometrically or dynamically and increase the effectiveness of the method [3]. In this way, whole-body EMS makes use of advantageous elements from conventional electromyostimulation and combines them into an innovative concept as a whole-body measure: by simultaneously activating agonists, antagonists and deeper muscle groups, the musculature can be trained more intensely and with greater endurance. Activating all the major muscle groups prevents one-sided strain and muscular imbalances, and offers an effective and time-saving way of building muscle and stabilising the musculoskeletal system for both prevention and therapy.
