some thots regarding bench pressers who have one leg leave the ground

[imnotbncre8ive]

Hi Mark. This thought crossed my mind recently, and perhaps it's so obvious as to be unworthy of mention. The only reason I bring it up is b/c you remarked (I believe in Strong Enough?) that you weren't sure why some newbie bench pressers have one leg raised off the ground during intense efforts.

My thought was that the one leg coming off the ground is a result of strength or effort assymetry. Let me try to describe what I'm picturing. Imagine that we are looking at a novice bench presser from 'behind' him, where the spotter would normally be. Our view is such that the bench and his body are horizontal (so our eyes are 'level' with his head and the rest of his body). As an example, imagine that the bencher has fully extended his right arm already, and is now working furiously to fully extend his left arm. His left arm is pushing as hard as it can against the bar, and it follows that the bar is pushing with equal force upon his arm. The bar is exerting more force on his leftside, and this is a torque that, if unopposed, would cause the bencher to roll off the leftside of the bench. That would suck if he did.

But, his left leg now pushes extra-hard against the ground to counteract this leftward-rolling tendency. In this instance, there is little use in having the rightleg push against the ground (doing so would only unbalance him further and increase his likelihood of rolling to the left). Thus, his right leg is unsupported by the ground. In fact, raising your leg from the ground (so that the ground exerts no upward force on your rightside) allows gravity to provide an unopposed moment on the rightside of your body and counteract your tendency to roll leftwards.

So my thought was simply that when a novice bencher is pushing extra hard on one side, he raises his opposite leg because it helps him shift more weight to the leg that would keep him from rolling off the bench (as well as allowing the weight of his raised leg, unopposed by a normal force from the floor, to help him stay on the bench).

I realize that a written description is very difficult to follow and piece together. If you like, I can draw a simple diagram of this.

[Mark Rippetoe]

I follow the description, but I disagree because it has been my experience that novice lifters do this even when the bar is level when they stick.

[imnotbncre8ive]

Only thing I can think of is that the trainee is trying to push harder with one side (the weaker side). I'm not sure how the bar position would change this.

If you can recall from experience, do most trainees have their right foot leave the ground? Or is it 50/50? From my idea, I would expect the majority of novice trainees who exhibit this to have their right foot leave the ground. My assumption is that most people are righthanded and their right upper bodies are slightly stronger as a result of years of favoring their dominant arm (for sports, etc).

[davew]

Maybe it's just a reaction to squirm/panic when uncomfortable. If someone's pinning you, most people automatically move and wiggle to try and get unpinned. Does it become less frequent as they progress to more advanced levels?

[Mark Rippetoe]

Dave is right, I'm sure. I have never noticed a predominance of one foot over the other.

[elVarouza]

I just think it's a general form issue with not realizing how to properly bench press. I.e. a lot of novice lifters, at least in my experience, don't understand how important it is to keep the upper back very tight during the movement. The upper back cannot be kept very tight under a heavy load if there's no leg drive.

In my limited experience teaching the bench press to people I always focus foremost on upper back tightness and I haven't yet seen someone flail their legs around.