by Bret Contreras February 02, 2010
Upon learning about my Electromyography (EMG) experiments concerning the glutes, many fitness professionals were skeptical. While some embraced my findings because it confirmed their long-held suspicions, others decided to brush it aside. I fear that some even turned against EMG and deemed it unimportant!
Many individuals in the fitness industry believe that conducting EMG experiments is a very difficult process that should be left to the highly-qualified researchers (I certainly felt this way before I learned how to use Noraxon’s Myotrace 400). While this may have been true in the past, technical advancements have made EMG experimentation very convenient and practical. I’m all for the peer-review process and journal publications, but field-practitioners (in this case coaches, trainers, therapists, and lifters) are some times years ahead of researchers. I prefer to be on the cusp of scientific advancement, so I don’t like to wait for the researchers to validate my theories; I prefer to test them myself!
Here is a video that details the EMG process using 6 different glute exercises (I apologize for the spandex but there’s really no way around it).
Electromyography measures the electrical activity of muscles during exercise. While EMG doesn’t directly measure muscular tension, the two should be very similar (although slightly off-set), as the electrical activity that EMG measures is simply a measurement of the nervous system’s signal to the muscles. Increased EMG activity is indicative of the nervous system’s attempt to produce more muscular force. The research indicates that EMG very closely models muscle force (tension) with isometric contractions. However, the more dynamic the movement, and the more fatigue that sets in, the more EMG strays from tension estimates. Moreover, with gross movements and surface muscles, surface EMG is fairly reliable, but with fine-motor movements and deep muscles, fine-wire EMG is required for accurate estimates.
I will be the first to admit that EMG isn’t everything. In fact, in order to determine an exercise’s effectiveness, I use several different tools/strategies:
1. Exercise Performance (do a few hard sets of the exercise with different levels of resistance and see where you feel the exercise working and at which ranges it produces the most tension, see if you “feel the burn”)
2. Biomechanical Analysis (consider the various muscle fiber origins and insertions, lines of pull at various joint angles, number of joints involved, types of contractions, directional force vectors, moment arms, joint actions, joint angles and ROM’s, joint torques, forces, powers, impulses, acceleration, accentuated regions of force development and torque-angle curves, total amount of muscle worked, speed of movement, etc.)
3. Functional Analysis (consider the movement pattern, number of limbs, muscles worked as prime movers and stabilizers, type of resistance, level of stability, level of support, system center of gravity, muscular transfer through the core, muscular transfer through the feet, kinetic chain type, multi-planar stabilization requirements, similarity to sport actions, joint-friendliness, coordination/activation requirements, mobility & stability, ability to correct fundamental movement patterns, etc.)
4. Muscle Palpation (actually feeling the muscles on yourself or another person with your hands and fingers throughout the duration of the exercise)
5. Delayed Onset Muscle Soreness (do a bunch of sets and see where you’re sore the following couple of days)
6. Electromyography (look at both mean and peak activity, mean is the average activity throughout the repetition, peak is the highest level of activity reached during the repetition)
7. Feedback (what do other lifters, coaches, trainers, and athletes have to say about the exercise?)
Kevin Neeld wrote an excellent article about EMG that can be found here, and Mark Young wrote an excellent blog about EMG that can be found here.
Having spent around 200 hours with electrodes hooked up to me while studying the electromyography of exercise, I have noticed a couple of phenomena with huge implications. First, muscle fibers within a muscle can function differently from one another. For example, during my research I have noted that the upper rectus abdominis and lower rectus abdominis function somewhat differently from one another. Similarly, I’ve found that the upper and lower fibers of the gluteus maximus function differently from one another as well. We’ve known that the various heads of the deltoids and pectoralis major function differently from one another for quite some time (which I also confirmed with my studies). I suspect that this is true of all muscles, as muscles often have varying fiber angles and attachment points, numerous motor units, and sometimes varying nerve suppliers. This might explain why athletes tend to see better results when they incorporate variety into their routines rather than sticking to just one exercise per muscle/movement pattern. I’ll publish more information about this in a future article.
Second, during a set the second rep usually produces higher EMG readings than the first rep. Perhaps the nervous system “figures out” how to better recruit the muscles following the first repetition. This might explain why Olympic lifters and powerlifters see better results when they perform multiple (albeit low) repetitions rather than solely heavy singles.
And third, there often seems to be a point prior to 1RM where muscle tension is maximized on a particular muscle. For example, in a bench press, you don’t get higher pectoral EMG when going from 90% of 1RM to 100% of 1RM.
Upon reading the data involving my glute experiments, many individuals in the fitness industry thought that something was awry when they saw figures exceeding 100% of MVC.
When you record MVC, you simply position your body in an advantageous position and squeeze your muscles isometrically as hard as possible. You can also use an immovable object to push against. In the case of the gluteus maximus, I’ve found that the highest my MVC values can get is if I get in the quadruped position and lift my thigh rearward with a bent knee (an isometric quadruped hip extension).
After recording MVC, every subsequent exercise you perform will be compared to MVC, as a percentage.
I would hope that a lifter like myself with 18 years of lifting experience could exceed MVC (an isometric contraction) through dynamic barbell, dumbbell, bodyweight, or band exercises. If we couldn’t exceed MVC through lifting, then that would build a strong case for isometric training (a la Charles Atlas) for bodybuilding purposes. But the reality is that strength training exercises will typically cause peak activation to far exceed MVC, and if the exercise is really good, mean activation can exceed MVC. If this happens, it simply means that the average activation throughout the repetition is higher than the average activation recorded from a maximum isometric voluntary contraction.
Researchers typically use mean MVC for their data. I used to think that mean MVC was more important as it showed the average activation throughout the entire repetition. However, muscles are not always active throughout the entire range of motion of an exercise, especially during compound lifts involving the hip. For example, during the hip flexion-extension axis, adductors act as extensors and flexors. In some exercises like the squat, the glutes are heavily involved down low but not as involved near the top. For this reason, I believe that peak MVC is a more important figure. Peak MVC is a measurement of the highest point of activation during the repetition.
I believe that mean activation might be more important for bodybuilding purposes in providing constant tension, while peak activation might be more important for sport-specific purposes in providing maximum tension at a certain moment. In this instance, you’d then have to look at the activation pattern (EMG-angle curve or EMG waveform), which shows exactly when the peak MVC moment occurred, and then compare that to a sport movement to see if it matches the timing parameters of that sport action.
I have also figured out how to get the most reliable EMG data, having spent so much time being “hooked up.” Here are some things I’ve noticed:
In general, exact results are very difficult to duplicate due to the variance of MVC. For instance, one day MVC for a muscle might be very high and the next day it might be slightly lower, which would yield different readings for the same exercise due to the fact that the readings are ranked as a percentage of MVC. It is important to look at patterns within the same session rather than absolute percentages, because the percentages will change from session to session.
1. If you’re a lifter, you can measure the mean and peak activity of not only your different muscles and muscle groups, but also the different sections of muscles, so you can learn which exercises work each area of the muscles best.
2. If you’re a lifter, you can also measure the effects of “tweaking” exercise form. For instance, widening a stance or grip width, flaring feet, switching hand position, altering the center of gravity, etc.
3. If you’re a writer, you can use EMG to validate or disprove theories.
4. If you’re a coach, trainer, or therapist, you can measure your athlete/clients’ EMG activity to see which exercises work best for the various muscle groups.
In all seriousness, the EMG experiments that I have conducted in the past year has caused my learning to sky-rocket. Usually, when I come across some surprising data and then consider why the results came out the way they did, upon analysis it makes perfect sense from a biomechanical perspective.
I hope you enjoyed this blog and learned something new!
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