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Archive for February, 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!

EMG Experimentation is Not That Difficult!

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).

What is EMG?

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.

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:

7 Ways to Determine Exercise Effectiveness

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)

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 load vectors, planar movement and stabilization, joint actions and torques, joint angles and ROM, contraction positions, accentuated regions of force development, total amount of muscle worked, speed of movement and force of contraction, lever length, center of gravity, 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, muscular transfer through the core, muscular transfer through the feet, kinetic chain type, 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?)

Prior Articles and Blogs

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.

Critical Findings

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, mid, 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.

And second, during a set the second rep nearly always 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.

Exceeding Maximum Voluntary Contraction (MVC)

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 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.

Which is More Important, Mean or Peak MVC?

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, 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.

Important Considerations for EMG Experimentation and Reliability

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:

1. Some deep muscles are impossible to measure with surface EMG and require fine-wire EMG
2. Some individuals suck at maximally contracting muscles isometrically, which will yield especially higher percentages during experiments when standardized according to MVC
3. Some muscles are harder to maximally contract voluntarily than others, which will also yield higher percentages during experiments when standardized according to MVC
4. MVC is inconsistent and varies from trial to trial, as even when you try to use the exact electrode placement and contract as hard as possible during MVC, it almost always yields different levels of MVC
5. This explains why the most reliable approach is to study all of the exercises in one session
6. MVC is joint-angle dependent; one has to know the best MVC positioning for each muscle (which can vary from individual to individual)
7. Electrode site placement is critical; improper placement can get interference from nearby muscles or body parts, or worse, it could measure the incorrect muscle
8. Electrode angle placement should be parallel with muscle fibers
9. External pressure from clothing can interfere with readings
10. Electrodes can lose their stickiness and start sloughing off or fall off completely, which can yield improper readings
11. Changes in muscle belly geometry can interfere with readings
12. Sliding of the skin in which the electrodes are placed can move the recorded area and interfere with readings
13. Explosive movements like sprints, plyometrics, jump squats, or Olympic lifts can sometimes yield unusually high peak EMG readings
14. Wires can get in the way while performing exercises, sometimes getting caught and ripping electrodes off in the process, which will pretty much end the session as when you place the electrode back on your readings will be skewed
15. Bumping an electrode during an exercise with the object used for resistance will throw the reading off considerably
16. During one-rep maxes there is no averaging of reps, which diminishes reliability
17. Choosing the interval period for the repetition is arbitrary
18. Range of motion and type of contraction are not considered, thereby giving partial reps and isometric contractions an advantage
19. Some individuals subconsciously flex and activate muscles during exercises which gives a false reading (you can squeeze the biceps as hard as possible on a squat; that doesn’t mean that they helped produce the motion)
20. Form varies considerably from individual to individual, and form can be purposely altered to favor a certain muscle or muscle group
21. Tissue characteristics can play a role in EMG readings, as some muscles are thicker than others and some muscles are located underneath fatty deposits
22. Skin preparation can affect readings
23. On a smaller scale, physiological and temperature conditions can alter readings
24. Neighboring cross-talk between muscles can interfere with readings, as can external noise like power hums and faulty grounding

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.

4 Ways That EMG Experimentation Can Benefit You

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.

Conclusion

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, it makes perfect sense from a biomechanical perspective.

I hope you enjoyed this blog and learned something new!

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