Interview: Prof. Dr. Kemmler Answers Important Questions

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Find out everything there is to know about whole-body EMS training: scientifically proven benefits, risks and target groups. Experts debunk myths and explain how whole-body electrical stimulation can be used effectively, safely and individually – from rehabilitation to fitness.

EMS training is becoming increasingly popular. Practical experience shows that the training is effective and safe. Nevertheless, prejudices and superficial knowledge persist, even though the use of ‘electricity’ originally comes from the field of medicine and healthcare. Today, the effects of EMS application have been scientifically evaluated and any risks are limited and calculable.

So if you don't want to rely on statements from providers or enthusiastic users, you can now consult current studies from well-known independent institutes.

For well over ten years, the University of Erlangen, under the direction of Prof. Dr. Kemmler, has been researching the application possibilities of whole-body electrical stimulation. In a recent interview, we asked him about the scientific perspectives, areas of application, risks and recommendations for EMS training.

Whole-body electromyostimulation (WB-EMS) is often advertised as ‘training without effort’. What is your opinion of this statement?

Prof. Dr. Kemmler: Hmm, that's an interesting question and depends on how ‘effort’ is understood. In fact, an appropriate application of electricity is an integral part of the current health WB-EMS method variant that generates the effects, so that the proportion of voluntary exertion remains relatively low. In training practice, this means that a suitably high stimulus intensity (via pulse strength) must be applied in close interaction between trainer and user, which should definitely be reported as ‘strenuous’. In particular, for WB-EMS users who are often less sport-oriented and have a correspondingly weak sense of exertion, this introduction to an appropriately high level of exertion and the development of a corresponding sensitisation of body awareness is the central ‘challenge’ for the trainer.

Critics often speak of little or no effect on functionality and coordination due to the ‘artificial’ activation of whole-body EMS training. What do you say to this criticism?

Prof. Dr. Kemmler: This opinion has since been refuted by a large number of EMS studies with significantly positive effects on a variety of functional parameters such as strength and performance. This argument may undoubtedly still apply to purely passive EMS application, but in training practice, especially in advanced therapeutic use, EMS is predominantly carried out in dynamics, i.e. using functional movements. Incidentally, this is where competitive sports applications differ from health-related applications. While competitive sports involve a high degree of voluntary activation with a moderate current intensity, which allows for an absolutely correct discipline-specific execution of the movement, the primary focus in the early stages of a therapeutic measure is on the current component as a stress instrument. However, this changes in the course of therapy, depending on the individual performance level of the patient. For older people, who need to positively influence muscle and fat mass in addition to (functional) training goals, a mixed training of both methods, ideally periodised with hypertrophically and functionally oriented sections, seems ideal.

A few years ago, the German Society for Clinical Neurophysiology and Functional Imaging (DGKN) warned against WB-EMS training. Can WB-EMS actually be harmful or dangerous?

Prof. Dr. Kemmler: This question regularly causes a stir in the media and unfortunately massively unsettles participants in EMS training. For this reason, we would like to address this question exhaustively and in a suitably differentiated manner within the scope of an interview. First of all, WB-EMS is definitely the training method of choice in our view with regard to acute orthopaedic and cardiac risks. A risk of EMS application that is repeatedly mentioned is associated with so-called rhabdomyolysis, in simple terms, stress-induced damage to muscle tissue. Due to its high sensitivity, CK (creatine kinase) is considered the primary serum marker of rhabdomyolysis. Based on resting CK values of below 200 IU/l, mild rhabdomyolysis is defined as an increase of up to 10 times, moderate rhabdomyolysis as an increase of between 11 and 50 times, and severe rhabdomyolysis as an increase of over 50 times the basal concentration. It is also important to note that there is a large intra-individual variance in CK concentration at the same relative load. In other words, some people react much more sensitively and with higher CK levels to physical exertion. In fact, WB-EMS is able to generate rhabdomyolysis due to the large number of muscle groups that can be stimulated simultaneously and, in extreme cases, supramaximally (i.e. higher than through voluntary innervation). A study closely monitored by a physician at our centre showed very high creatine kinase and (to a lesser extent) myoglobin values after the initial EMS application with individually maximum tolerable stimulation levels. On average, but not for all participants, these values were in the range of severe rhabdomyolysis. However, in line with the available literature, no clinical consequences were observed. Whether this result can be transferred to users with health limitations remains to be seen. However, a key finding of the study was that a very pronounced conditioning effect was observed in all subjects during the further course of WB-EMS training. In fact, after ten applications of EMS and another WB-EMS at full capacity, a 30-fold reduction in CK values was demonstrated, i.e. a concentration in the range of conventional strength training. The problem of EMS-induced rhabdomyolysis is therefore largely based on the application of inappropriately high-intensity electricity during the initial sessions. We have presented guidelines in the ‘Guidelines for the safe and effective application of whole-body electromyostimulation’ that comprehensively address this issue.

Your team at the University of Erlangen has been conducting research in the field of whole-body EMS for a long time and has played a major role in the guidelines for safe and effective use. In your opinion, what are the most important rules of conduct that a provider of EMS training must follow?

Prof. Dr. Kemmler: From our point of view, the focus is clearly on effectiveness and safety when using EMS. As already discussed, EMS is not an all-time effective and absolutely safe application that is a sure-fire success. In fact, to a greater extent than with other training methods, competent and trusting interaction between the user and therapist is the key feature of a successful and safe therapy measure for generating the best possible result. For this reason, we consider 1:1 supervision to be an important criterion for therapy. For preventive training, the supervision ratio is a maximum of two trainees per supervisor.

In addition, it is important that the provider has appropriate therapeutic and/or sports science training in order to ensure long-term success with regard to applicable training principles, contraindications and the recognition of certain load parameters for different clinical pictures. In terms of contraindications, the development is certainly not yet complete. In particular, in therapeutic and medical use, some absolute contraindications are currently changing to relative contraindications. In the therapeutic segment in particular, we expect to achieve greater safety through scientifically based findings, through education and cooperation with doctors and clinics.

The heart is also a muscle. Why is the heart not affected by the electrical impulses of electromyostimulation?

Prof. Dr. Kemmler: Like every muscle, the heart muscle also contracts when electrical signals depolarise the muscle fibres above a certain threshold. In this way, the heart is brought to rhythmic contraction via the autonomous conduction system. In principle, the heart muscle can also be influenced or disturbed by external currents, as can happen in the event of an electrical accident or during resuscitation with a defibrillator. In contrast to a socket or a defibrillator, which generate very high voltages and currents, the current intensity is very low during EMS application and the current flow is regionally limited. This is because extremely low currents are sufficient to activate the skeletal muscles. The main effect of electromyostimulation with low-frequency currents is the activation of the small motor nerve branches near the electrodes. If these are depolarised by the external current above a certain threshold, the nerves generate an action potential that automatically propagates in the direction of the muscle fibres and activates them. The fact that the external current ‘initiates’ the body's own physiological excitation means that the muscles are also activated in the depths and stimulated to a strong contraction. However, there is no relevant current flow outside the skeletal muscles through the chest to the heart. Nevertheless, cardiac arrhythmias and, in particular, pacemakers are a contraindication that should be strictly adhered to as a precaution. The positive cardiological effects of medical EMS training have been scientifically proven in a study at the German Heart Centre in Bad Oeynhausen.

For several years, functional training has been considered a highly effective method for quickly and effectively achieving fitness and health goals. How do you see the connection/difference to EMS training here?

Prof. Dr. Kemmler: The comparison is actually interesting: functional training is often presented as the exact opposite of EMS training, since the focus is on exercises with complex movements involving several joints and muscle groups, while EMS, at least in the past, always had the aspect of statics and not functionality in mind. Now, modern and especially therapeutic EMS training is rarely applied statically, but predominantly dynamically. During their individual EMS training, therapists in particular prefer movements that are relevant to everyday life, involving several joints and, as far as possible, a large amplitude. In order to generate the necessary above-threshold intensity, classic functional training often uses various additional loads. With EMS training, the intensity is primarily controlled by the current pulse. The latter aspect contributes to a more favourable orthopaedic tolerance and lower risk of injury, especially for inexperienced and/or less athletically trained individuals. Aspects such as a limited time budget, health orientation/health limitations, little affinity for conventional training and excellent intensity control speak in favour of therapeutically guided EMS training.

In your opinion, who is the actual target group for whole-body EMS training?

Prof. Dr. Kemmler: Due to the training being particularly easy on the spine and joints, without heavy weights or pressure, EMS training can be used at an early stage and in parallel with individual physiotherapy treatment. Combining it with the functional exercises relevant to everyday life, as mentioned above, gives us an inexhaustible target group that is also unlimited in terms of time. Following the guidelines of ‘easy to hard’ and ‘simple to complex’, we address both young and old, trained or untrained, healthy or sick/injured. EMS training is therefore at least as widely applicable as conventional strength training. In our research group, we are currently specialising in musculoskeletal and cardiometabolic diseases and conditions, which are mostly associated with old age. Recently, more and more other target groups and areas of application have emerged. Through a research network with other scientific and medical institutions, we will continue to advance EMS research, identify important and meaningful areas of application and evaluate them together in the future. I think that EMS research will develop more prominently internationally in the next few years, so we can expect even more exciting research results on this topic.

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