By Carl Valle
Electromyography (EMG) is not new, and recently there has been some confusion about it among both sports performance coaches and sports medicine professionals. There is increasing access to electromyography due to smart fabrics and wearable technology evolution, and teams and colleges facing more and more pressure from their superiors for more data.
My motive for this article is to ensure that those interested in using EMG in their environment do their homework on the ways they can benefit from the technology, and be honest about what they need to do to get good data. EMG is not for everyone, but if you are serious about the information it provides and wish to dive in, you must commit to the protocols and understand the limits on what the data can tell you.
EMG Readings – Limitations and Usefulness in Applied Settings
I spend most of my time with EMG reading the vast amount of research that attempts to solve much of the mystery of what goes on in movement and training. I have used EMG for complex injuries, and have performed a few investigations on performance myself. Of all the data available, I find EMG the most demanding to interpret. While some great software exists, deciphering a short explosive event in sport with EMG is something I still can’t do without the help of fellow coaches and sport scientists. It’s not that the science and practice is not there to understand the readings, it’s just that the subtitles of biomechanics and interventions are still uncharted.EMG is a very demanding investment, and you must put in the effort and time to get any benefit. Click To Tweet
If coaches and therapists can remember one key point, it’s that EMG is a very demanding investment and you must put in the effort and time to get any benefit. It’s not like velocity-based training or electronic timing, where the data is instant and obvious. It’s not even like force analysis, as the data is not a direct measure and requires far more interest and knowledge than may align with the environments of most sports staff. Still, it can make a difference if you use it right, but you must be dedicated to both the process and education required.
A Better Way to Look at EMG Physiologically in Sport
We were exposed to electromyograms in kinesiology and exercise physiology, but we didn’t use the instrumentation because it was more appropriate for advanced students. When I interned at the MLB, the Chattanooga EMG Retrainer was my first exposure to electromyography; of course, I experimented on myself during squatting to see if my core was the limiting factor in the amount of weight I could lift. It was an awkward and ineffective attempt at primitive sport science, but the thought process was right on. Today, we see new research posted almost daily using EMG as evidence for a hypothesis. If the researchers make interpretation errors, how do we expect coaches to juggle the same information while managing other forms of data like player tracking and velocity-based training?
The easiest way to look at EMG data is to either dismiss it or worship it because it fits a narrative or agenda. The mature way of looking at EMG is to accept it, as evidence provides clues to what happens during its activity. Electromyography, specifically surface EMG (sEMG), is the rise and fall in voltage of superficial muscles appraised by two electrodes. There are a lot of factors regarding the noise and signal challenges of estimating the activity of a muscle. Placing conductive stickers on superficial muscles creates many challenges that are beyond the scope of this article.
Skin is extremely dry and “dead” compared to the wet and salty internal environment of the body. Skin is the largest organ of the body and designed to protect us from microscopic invasion, and most of that resistance (99%) comes from this amazing layer of cells. Current (the amount of electrons that flow per second), which is measured in milliamperes, is not measured by EMG, but electrical stimulation is a component when performing medical diagnosis of neurological problems. EMG is a signal, not a direct measure of muscle activity. Regardless, dismissing electromyography because it doesn’t solve the world’s problems is foolish and the criticisms are usually from those that don’t like the findings of experts who see EMG abused for marketing purposes. Raez and colleagues state in their review, “Techniques of EMG signal analysis”:
“EMG is sometimes referred to as myoelectric activity. Muscle tissue conducts electrical potentials similar to the way nerves do and the name given to these electrical signals is the muscle action potential. Surface EMG is a method of recording the information present in these muscle action potentials.”
This explanation details that myoelectric activity is simply information about action potentials, rather than what is happening neuromechanically with all of the muscle fibers. Everyone who is first introduced to EMG has likely heard the analogy of someone listening through a wall with a glass and hearing the noise of a group. While it’s too difficult to determine who is talking, we know what neighbor it is (muscle), when they were making noise (time), and how loud they were (possible peak and mean values). The limitations of surface, and even fine wire EMG, is that it’s an electrical biosignal and summary, not a direct measure of specific physiological functions.
Sometimes I develop a brain fog when juggling voltage units, motor unit recruitment, and amperes with the Bioelectric Triad. The Bioelectric Triad is an interconnected way of managing muscle function with tensiomyography and electrical muscle stimulation, as well as electromyography. When I talk to other coaches and sport scientists about EMG, it’s more about timing and location than about hard physiological promises like strength and performance from EMG. Always factor in a direct and specific transfer and adaptation when using electromyography, as long-term results are actual training interventions, not the peak or mean values of sEMG tests in a few acute studies.
Valid Approaches and Common Errors with EMG
Research equipment evolves from improvements in data quality, speed, and often miniaturization (size) of the instrumentation. As technology improves and changes, remember the body is basically the same and we still must contest with the laws of biology. Even if a product is cheaper or easier to use (read: more accessible), you must account for the science being just as strict as it was before the system went on the market. Logic and reasoning are future-proof, as biology sometimes changes based on new information, but coaches have to be skeptical even when pressured to look “cutting edge” by athletes, team head coaches, and management.
Video 1. I highly recommend that you perform your own validation and see if different entry EMG products actually provide quality data and make a difference in your training. There are a lot of videos for commercial EMG, and I am not sure what they find of value except marketing their training facility.
A far more technical and scientific outline on the limitations of EMG exists, and that document can only add more detail to the problem. I have included a list of growing pitfalls and false roads that are emerging because of the increase in EMG interest, and also share viable alternatives that may help teams and coaches advance their program. I already explained some of the scientific limitations of EMG and how interpretation needs to be cautious and have lowered expectations, but sEMG is very useful in certain circumstances. Instead of talking more about the science, it’s a good time to talk about training and coaching.
Modeling Performance vs. Measuring Mechanical Strain
Coaches want to measure training with more precision, but using EMG for stress loads is wishful thinking. Modeling, or simply having a good plan that you can track and evaluate, can use EMG research to improve the process of the program. Modeling creates a strategic outline of needs and ways to evaluate the plan over time. Nobody expects the model to be perfect with inputs and outputs, just to be better than a “play it by ear” or “wing it” approach.Coaches want to measure training more precisely, but using EMG for stress loads is wishful thinking. Click To Tweet
Attempting to measure mechanical stress on muscle groups using EMG is not appropriate. More activity may relate to more use of muscle specific groups relatively, and high EMG readings are part of the picture of connecting hypertrophy and strength but can’t be seen as direct connections. Bodybuilding and sports training are more than activation of muscle, as nutrition and systemic effects of exercise are also extremely important in the equation.
Hypertrophy can be achieved with low load training, so intensity and stress are not a clear connection with EMG. Add in blood flow restriction (BFR) training, and EMG alone can’t explain why muscles are getting larger and stronger. Power and other forms of strength are more than just how much activation shows up on the “voltage meter” and the biology of volitional strength is more complex than amplitudes of surface EMG in studies. I made the mistake of reading some of the earlier studies on hormone and EMG research and assumed the relationships between strength training and androgens magically connected via the interpretation of EMG. I, like the researchers, oversimplified the connection.
Like lactate and pH changes to blood, fatigue and stress will create a transient change in biochemistry and bioelectric responses, but EMG findings are not indications of the magnitude of strain on the tissues being read by the electrodes. I found it naturally very hard to move away from the idea that muscle activity and strain are not synonymous. On paper, high activity can seem like high stress at first glance, but the science doesn’t agree with that conjecture. Instead of placing too much demand on EMG and expecting it to be a direct measure of mechanical load of muscle, see it as more of a timing and amplitude of the signal.EMG is more a timing and amplitude of the signal than a direct measure of mechanical load on muscle. Click To Tweet
Most of the strain estimations will come from modeling muscle groups based on motion capture, force analysis, and some EMG data to connect the data points. The use of EMG for the management of training strain locally is not there yet. With over a hundred muscles that contribute to propulsion and deceleration—many of them at risk—it’s better to spend time determining if they are prepared for mechanical work rather than continuous monitoring. Unless a known issue that is specific and easily recognized later in the readings is present, EMG can’t do everything.
Return to Play vs. Monitoring Training Loads
Function and fatigue are the two main variables that sports medicine and sports performance coaches think about with regards to preparation, injury risk, and overall performance. Monitoring training has two goals: knowing how to load the athlete to optimize game day performance and reducing the incidence of injury from being too conservative or too reckless with cumulative work. Some teams hope that wearable EMG is the solution to local injuries; however, while more data is nice to have, how many teams are really equipped to handle this type of data?
Monitoring training loads is a theoretical concept with EMG, as work calculations from wearable surface systems are a major undertaking. Creating useful metrics from EMG to estimate work during complex practices and games with entire rosters is a pipe dream for most environments. You cannot use EMG and effort interchangeably, as the readings of a few muscle groups don’t represent the body and the stress of the training or competition (if the technology is allowed).
Return to play or return to performance is another story, as surface EMG makes sense in some circumstances, especially if the baseline symmetry data is meaningful. There are countless times when an arbitrary threshold is created, and coaches are unable to effectively understand how left and right or front and back asymmetries live in an athlete’s body. For example, an athlete with a lower activation of a specific muscle could be more efficient because of improvements in mechanics or another muscle group contributing more, so a decrease in activity may be a good thing. Asymmetries are normal most of the time, but interpreting why and how an asymmetry affects an athlete is extremely tedious and you can’t do it conveniently with a “gadget.” If the athlete is educated and the staff is very skilled, some EMG information may be helpful, but only mainly in early stages.
Exercise Selection vs. Exercise Adaptation
Electromyography helps with exercise selection, including sport-specific activities such as practice. EMG alone is not enough to determine the best exercise or modality to use, but it’s a primary factor. Biomechanically, EMG fits nicely with strength training, jump training, sprinting, and even throwing. Using EMG to choose the right modes of training makes sense, but beyond muscle groups, using electromyography to study adaptation is far less effective.Using EMG to choose the right modes of training makes sense. Click To Tweet
The issue with EMG is not that it doesn’t do a good job of evaluating all of the physiological activity of the neuromuscular system in fast motion, it’s just that biosignals are not effective in explaining central adaptations because it’s mainly a peripheral solution. Cellular changes to muscle and other tissues from other physiological adaptations are part of the adaptation or improvement equation, and EMG simply can’t explain those. In addition to biochemical, neurological changes are impossible to pick up via surface electrodes or even with fine wire. What EMG can likely support is the added clarity of rate of force development and similar connections to explosive strength with additional measurements. There are some interesting findings on how motor units fire and EMG enables deeper understanding, but those are at the molecular level and without information from the CNS, so the picture is incomplete.
Adaptation without transfer is just evidence of poor direction and time, since athletes need to get better at their sport, not just raise the metrics of theirs that have poor contribution to success. Adaptations may not immediately show up in performance enhancement, but they have to have a chance to improve an athlete on paper and show value in the research. Most of the challenge with performance changes is that even significant changes or improvements in training may not easily demonstrate value. An athlete may improve their speed in testing but games may not always provide an opportunity to showcase those enhancements.
Biofeedback Rehabilitation and Neurological Examination
My biggest pet peeve with bad sport science from coaches is them talking about “seeing” a muscle not firing, which started with core muscles in the 1990s. Later, the shutting down of muscles got worse with “glute amnesia” hype and activation in the early 2000s. We learned from the misdirection on muscle recruitment that EMG was not the culprit—it was the experts (real or self-promoted) who were wrong.
Loose language and talk about muscles not firing is negligent, and approaches pseudoscience. The core issue with neuromuscular performance is that absolute statements about muscles unable to fire (or shut down) is more of a disuse issue and not a functional state. You can find plenty of options for muscle diagnostics in the review guide to explain options outside of EMG.
Electrodiagnostic information is not common unless it’s for a major trauma to the nervous system or a disease state is expected. This was necessary for three contact sport athletes that I worked with, all due to football, and all involving career-ending or near career-ending injuries. It is extremely rare to need this type of medical testing in other sports. Some athletes have nerve stimulation performed to ensure that a known stimulus provides a twitch response, but I have only witnessed this. I recommend that teams and colleges outsource this because it requires specialized training and experience to evaluate the assessment.
Biofeedback is another story, as athletes will need assistance to “learn” to trust their body after injury. The case for biofeedback ranges from post-surgical demands to fine-tuning movements in sport or training. Biofeedback can range from a traffic light or near binary response of on and off experiences to something more quantified like thresholds and target ranges. In my experience, biofeedback is especially helpful for athletes who need to build confidence in themselves, and especially in the injury site.
One warning, though: Focusing too much on a muscle can lead to the problem of an athlete obsessing over their injury. This can be a nightmare later, as they become dependent on a number or equipment to guide them. A short period of time using biofeedback is enough to calibrate their confidence and teach them to trust their movement competence and internal subjective feelings of muscle contraction.
Final Thoughts on Electromyography Outside the Research Walls
I hope I have not scared support staff away from using EMG or promised anyone that the tool will save an athlete’s career. EMG has helped me learn more about what I don’t know and reinforce what plenty of people before me already know about the human body. Most of the applications for EMG should be left to talented and experienced researchers, but clinicians and crafty performance specialists can honestly benefit by using electromyography with their athletes.Have a realistic, attainable goal in mind before you get involved with EMG for direct measurements. Click To Tweet
If you plan to get involved with EMG for direct measurements, you must have a goal that is realistically attainable so you can make real decisions that you could otherwise not have made without it. I am experienced enough with EMG to warn those that are new that it’s not something you can jump into and make a difference in training or rehabilitation right away. But remember: If EMG helps just one athlete achieve a dream in sport, it’s worth it.