Stance width and bar load effects on leg muscle ac

[QuantumPositron]

Stance width and bar load effects on leg muscle activity during the parallel squat.

Applied Sciences
Medicine & Science in Sports & Exercise. 31(3):428-436, March 1999.
McCAW, STEVEN T.; MELROSE, DONALD R.

Abstract:
Stance width and bar load effects on leg muscle activity during the parallel squat. Med. Sci. Sports Exerc., Vol. 31, No. 3, pp. 428-436, 1999.

Purpose: Altering foot stance is often prescribed as a method of isolating muscles during the parallel squat. The purpose of this study was to compare activity in six muscles crossing the hip and/or knee joints when the parallel squat is performed with different stances and bar loads.

Methods: Nine male lifters served as subjects. Within 7 d of determining 1RM on the squat with shoulder width stance, surface EMG data were collected (800 Hz) from the rectus femoris, vastus medialis, vastus lateralis, adductor longus, gluteus maximus, and biceps femoris while subjects completed five nonconsecutive reps of the squat using shoulder width, narrow (75% shoulder width), and wide (140% shoulder width) stances with low and high loads (60% and 75% 1RM, respectively). Rep time was controlled. A goniometer on the right knee was used to identify descent and ascent phases. Integrated EMG values were calculated for each muscle during phases of each rep, and the 5-rep means for each subject were used in a repeated measures ANOVA (phase x load x stance, [alpha] = 0.05).

Results: For rectus femoris, vastus medialis, and vastus lateralis, only the load effect was significant. Adductor longus exhibited a stance by phase interaction and a load effect. Gluteus maximus exhibited a load by stance interaction and a phase effect. Biceps femoris activity was highest during the ascent phase.

Conclusion: The results suggest that stance width does not cause isolation within the quadriceps but does influence muscle activity on the medial thigh and buttocks.

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The results of this study are congruent with others I have posted.

 

[quadancer]

I'd like to add an opinion.
You can change your stance to acheive a more pronounced workload on the "tail end" (because chicks dig squat butt; S.J.) but overall your best position is going to be for more ability. If you have more lifting ability, you can lift more (doing more work) and henceforth grow more. Including butt. I think this is one time when science has to take a back seat to brologic.
If you alter your position from your optimum, you will lose ability and do less work overall, possibly reducing GH spikes, and et cetera. Unless you just want more butt.
Butt that's all I wanted to say.  

 

[Martin Levac]

More efficient leverage won't put more strain on the muscle applying the force. It will however allow a greater load to be lifted. The sumo stance starts closer to the ground and ends closer to the ground as well. There is no or very little flexing of the knees with the sumo stance. Only flexing of the hips. For those reasons it allows a much greater load to be lifted. The sumo stance won't make us bigger but it will certainly make us look stronger. We find the same phenomenon with any exercise that uses shorter ROM. The most eloquent is the guy lifting a car an inch with his legs pushing up.

 

[quadancer]

Hmmm...with extremes like that aside, I would think that there would be a limiting factor in the less-than-optimum stance. That's really what I was trying to say. You are then transferring load somewhat to other muscles.
Your point is well taken in regards to ROM changes; less distance equals more leverage.
But then one has to consider other factors as well; there are other reasons sumo stance is used apart from more leverage: it involves torso/leg length ratios and body mechanics. It's not always advantageous to everyone. Whilst my deads are possible with sumo, my squat is traditional. I'd rip a hip doing sumo in a squat.
And yes, there may be a 2" advantage of shorter ROM, but also consider that the load is still being lifted by something, namely the extensiors and gluteus.
I believe that when a limiting factor is involved, (less than optimal position) you get a lower ceiling you can ascribe to. Even with time and practice you would sooner hit your lift limits for your age, weight and height than if you were to optimise.
I found this out first with bench press; going wide was killing me for maxes...and that's another exersize where even with a shorter ROM the exersize is harder. I simply have to use my arms more and leave my shoulders alone, or I'd have to stop benching.
This is not necessarily negating your point however; I feel that all these exersizes have individual-specific values not considered in the study, although I'd consider squats to be more of an even playing field than the other exersizes.For deads, I'd have dropped off long ago with weight, and I don't think this new growth (howeversmall) to my thighs would be apparent. Were I ABLE to do traditional deads, I believe there would be possibly more growth due to a longer ROM, were the loads equal, but the limiting factor of position does not allow very much progression.
I'm not sure I'm making my point very well, but the study points to a "right now" scenario, whereas I'm talking from a BB'ing standpoint of growth over time.