I know I’ll be crucified for this, but I’m about to write about a study I haven’t read yet (gasp).
A client told me about a study she saw in amNew York (a free daily we get here in NYC) regarding muscle activation – specifically, which exercise activates the glute muscles the most. According to the study, glute kickbacks (or mule kicks, or butt blasters, or whatever else you want to call them) caused the greatest muscle activation. She used this article as evidence that she should be doing said exercise for the greatest possible glute development.
***Insert tirade here***
Well, here’s the skinny on muscle activation studies:
To test muscle activation, what researchers do is stick electrodes either on the surface of the skin overlying a given muscle group or (less frequently) a needle electrode is used and the researchers will stick the needle under the skin, into the muscle group. What the researchers intend to measure is the electrical activity of the muscle group – the size of the action potential that causes the muscular contraction. The greater the action potential, the greater the “activation” of the muscle group (how well it is being recruited to perform the work).
Sounds pretty reasonable, and it is. Here are the confounding factors:
1) Researchers will typically use the non-invasive EKG-style electrodes (the kind that do not break the skin), which introduces error into the measurements.
2) The aforementioned electrodes (as well as the subcutaneous ones) will tend to pick up any activity and reflect it as “noise” (a wave on the oscilloscope), further obscuring the reading. In other words, the movement of your skin over and around the electrode can and does get picked up as “activity.”
3) Muscle groups have different areas of activation in different areas of a given movement (known as differentiation). As a purely hypothetical example, in a lat pulldown, the top portion may be preferentially recruited in the first 40 degrees of movement, while the bottom portion closer to the insertion point may be preferentially recruited in the final 50 degrees of movement.
Given these shortcomings, I find it hard to swallow claims based on EMG studies. Which is not to say that all EMG studies are performed poorly, but given the impreciseness of the testing tools, I would regard all results from EMG studies with caution. Read the Procedures section of the study and decide for yourself.
Personally, I find it hard to believe that more glute development would occur from butt blasters than a properly performed set of stiff-legged deadlifts. But that’s just me.