One of the questions I’m often asked by coaches, athletes and practitioners when talking about Electrical Muscle Stimulation (EMS) is about the volume and the frequency of use.

Lack of formal education, as well as a general tendency to avoid daily “experiments”, are the main reasons why coaches often feel uncomfortable in planning and integrating EMS into the regular training schedule of their athletes.

Another important factor, often contributing the most toward this negative trend, is the misinterpretation of the outcomes of muscular contractions induced by EMS devices: sometimes the lack of “dynamic movement” associated with Electrical Muscle Stimulation, has lead coaches to think of EMS as something easy that requires almost no effort.

As this is not the case and training sessions with EMS can be very demanding in order to elicit biological adaptations, I will try to provide some guidelines, dictated by evidence and practical applications, for the implementation of EMS technology into the process of training design.

Understanding EMS contractions

Integration of EMS into regular training does mean that basic muscle physiology concepts need to be well fixed and understood: first of all, an EMS contraction is like a loaded muscle activity. During a contraction induced by external current application, a high level of evoked force is created (Vanderthommen and Duchateau, 2007), resulting in muscle tension being applied to neuromuscular structure.

It is normal to deal with very uncomfortable levels of muscle soreness for those athletes who are unfamiliar with Electrical Muscle Stimulation: given the different nature and characteristics of motor unit recruitment, even advanced athletes regress as a beginner with EMS training.

The metabolic fatigue associated to EMS contractions (Vanderthommen et al, 2003) is likely to cause a level of muscle soreness which is higher than that occurring during voluntary induced muscle contractions (Jubeau et al, 2008).    

With this in mind, proper understanding of the nature of electrically stimulated contractions is paramount for coaches in the process of designing a training program.

The first obstacle that coaches usually encounter is related to the “how much” and “how frequently” question; to properly understand how to apply the right load through EMS we need to make a primer on basic muscle physiology and electricity theory.

As summarized by Gregory and Bickel (2005), the motor unit recruitment pattern of electrically stimulated contractions is nonselective, meaning that both fast and slow fibers are being activated no matter the intensity used, spatially fixed and synchronous.

In EMS training, we normally use both muscle twitches as well as tetanic contractions in order to elicit different biological responses:

• gentle muscle twitches are normally used in recovery programs with medium to low frequencies
• tetanic contractions are used in strengthening programs generally at frequencies ranging from 50 to 150 Hz

This is one of the most important aspects to understand during the first approach in designing a training program with EMS integration as the type of muscular contraction being used has its own influence in terms of fatigue, recovery and adaptations.

Also, the ability to recruit fast fibers at relatively low-force levels (Gregory And Bickel, 2005) is key in understanding the timing of EMS dosage.

The four main aspects of EMS training design

In my experience there are four fundamental aspects that every coach, starting to implement first time EMS in training, needs to properly take into account:

1. EMS as an integration method
1. Electrical Muscle Stimulation is an integration method not an exclusive method of training, meaning that the outcomes of its application are directly related to the efficiency of the regular training design. Whether the EMS training is scheduled in a dedicated training session or in addition to the regular session, it needs to be carefully designed in association with the main performance goals and outcomes of the given training cycle.
2. Considering progressive overload and specificity
1. For EMS training the same concepts and biological rules of regular training applies: the concept of progressive overload and specificity are essential in training design.
2. Progressive overload with EMS refers to the frequency and intensity (current amplitude) settings with higher frequencies and intensities corresponding to higher loads and muscle tension (evoked force) applied to neuromuscular structures.   
3. It is always advisable to start at lower intensities for strength training programs to get accustomed to the new type of stimulus and then progress over time based on individual responses and tolerance.
4. Specificity in terms of muscle action and prime movers is important to drive decisions about pad placement and stimulation parameters.
3. Considering training objective
1. Periodization is paramount in order to maximize the outcome of electrical muscle stimulation.
2. When designing a plan, you need to schedule weekly frequency and stimulation parameters as well as duration based on whether you are training for maximum strength, power or muscle endurance. Like in regular training, different training objectives requires variation in weekly frequency, stimulation patterns and rest intervals between contractions.
4. Timing of session
1. Scheduling an EMS session as an individual workout or in the same session of regular training is another important piece of the puzzle.
2. Again, considering the weekly sessions available as well as the training goals can help in choosing the right timing.

With EMS training session alone, it is possible to dedicate more time to the process of specific adaptation to the EMS stimulus as well as using more volume of work and higher intensities. With EMS and regular training in the same session, EMS is able to amplify the adaptation process by providing an extra-stimulus at the end of the session without excessive extra-stress and fatigue (due to the ability to stimulate fast fibers at relatively low-levels of force, i.e. lower intensities).   

In the next articles, I will provide some practical PainPod applications for hamstrings and upper back muscles.