The Effect of Back Squat Depth on the EMG Activity

Q

QuantumPositron

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The Journal of Strength and Conditioning Research: Vol. 16, No. 3, pp. 428–432.
The Effect of Back Squat Depth on the EMG Activity of 4 Superficial Hip and Thigh Muscles
ANTHONY CATERISANO, RAYMOND F. MOSS, THOMAS K. PELLINGER, KATHERINE WOODRUFF, VICTOR C. LEWIS, WALTER BOOTH, and TARICK KHADRA

The Department of Health and Exercise Science, Furman University, 3300 Poinsett Highway, Greenville, South Carolina 29613

ABSTRACT

The purpose of this study was to measure the relative contributions of 4 hip and thigh muscles while performing squats at 3 depths. Ten experienced lifters performed randomized trials of squats at partial, parallel, and full depths, using 100–125% of body weight as resistance. Electromyographic (EMG) surface electrodes were placed on the vastus medialis (VMO), the vastus lateralis, (VL), the biceps femoris (BF), and the gluteus maximus (GM). EMG data were quantified by integration and expressed as a percentage of the total electrical activity of the 4 muscles. Analysis of variance (ANOVA) and Tukey post hoc tests indicated a significant difference (p < 0.001*, p = 0.056**) in the relative contribution of the GM during the concentric phases among the partial- (16.9%*), parallel- (28.0%**), and full-depth (35.4%*) squats. There were no significant differences between the relative contributions of the BF, the VMO, and the VL at different squatting depths during this phase. The results suggest that the GM, rather than the BF, the VMO, or the VL, becomes more active in concentric contraction as squat depth increases.
 
That's unseemly. (is that a word?) The biceps femoris is stretching further in the ATG squat, so how can it not be involved more? I'm not sure of the tie-in to the glutes, but it also seems that they are pulled by the femoris, but perhaps not. Have to study a chart for that. Anecdotally, I feel my hams in the ATG way more than in parallell work.
Or did that last line mean to suggest that they all increase activity, but not as much as the GM?
 
I dunno either Quad. Perhaps I'll come across other studies looking at the same thing. I have studies showing that inclines do not increase upper pec activity any more than the flat bench, and studies that say the opposite.
 
Here we are. This is taken from a review which means I cannot post the article in its entirety legally. Here is the relevant portion though. The name of the article is "The Role of the Back Squat as a Hamstring Training Stimulus." Citations follow.


<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">Jensen and Ebben (4) examined the realtionship between squat depth and hamstring motor unit activation as assessed by surface EMG. Results revealed that hamstring motor unit activity did not change as a function of depth during the concentric portion of the back squat. During the eccentric portion of the back squat, hamstring activitiy did change as a function of squat depth. Hamstring activity was greatest at 120 degrees or less of knee flexion (Figure 2) . Results suggest that during the back squat, the eccentraic role of the hamstring is greater than the concentric, and that the eccentric activity increases to a degree as a function of squat depth. It was not possible to determine if the EMG activity during the concentric phase is a result of the hamstring functioning as a cocontractor and stabilizer or if the hamstring plays a role as an agonist assisting hip extension.</div>

Source:

&quot;Strength and Conditioning Journal: Vol. 22, No. 5, pp. 15–17.
The Role of the Back Squat as a Hamstring Training Stimulus
William P. Ebben, MS, MSSW, CSCS *D and David H. Leigh, MS, ATC

Marquette University, Milwaukee, Wisconsin
Randall L. Jensen, PhD

Northern MIchigan University, Marquette, MI&quot;

Here are the references cited in the quote if you wish to dig deeper:

4. Jensen, R.L., and W.P. Ebben. Hamstring electromyographic response of the back squat at different knee angles during concentric and eccentric phases. Proceedings of XVII International Symposium on Biomechanics in Sports. Hong Kong. 1:158–161. 2000.

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FYI: 120 degrees or less of knee flexion is about 1/2 of the way down a parallel squat, judging by the picture. So the deeper you go past this point during the eccentric phase, the more the hamstrings activate - but only during the eccentric phase according to this research.
 
Just remember, EMG activity isn't everything. It is a decent indicator, but not the final word. Also, it's going to vary based on your own personal form, body mechanics, etc.
 
thanks for posting these studies QP, interesting stuff.

I agree w/ Quad on growth being a good indicator. and add; my ass gets more &quot;sore&quot; going ATG than otherwise.

&lt;ducks&gt; whoa! I didn't say soreness was a scientific indication.
 
Ah of course. Growth. Well I don't perform studies, I just sift through 'em. Perhaps this is a naieve assumption but I've always presumed that more EMG activity = more muscle activity = more tension.

I am a deep squatter too and I was hoping to see some study telling me how to adjust my squat to better stimulate the vastus medialis. At least now I know how to get a bigger butt. Seriously though, I like squatting deep. Leg strength transfers over to everyday life and I like to know I can safely come off the ground with a load (moving furniture up stairs, hauling wood, etc.).
 
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