ExRx.net

So maybe Brett Contraras wasn't completely out to lunch after all?

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Let thy food be thy medicine, and thy medicine be thy food.~Hippocrates
Strength is the adaptation that leads to all other adaptations that you really care about - Charles Staley
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Thanks TimD

I knew it!

Dub mate, next time you're in Glasgow I'm buying you a pint

I think the greater activation of the hip flexors could account for that reading. We also have no way to account for those readings being that way from a physiological perspective. So while the readings may be proven, thinking it comes from emphasizing the lower abs is simply presupposition, without some sort of mechanism for how it is possible.

Well, I went back to my old anatomy text and reviewed rectus abdominis. It is innervated by the lower 6 or 7 thoracic nerve-root segments. So since it has multiple nerves, it makes physiologic sense that regions of the muscle could be more or less active than others. If T6 is firing, the more superior fibers of rectus will contract. If T12 is not firing at the same time, the inferior fibers will not be contracting. So it's a very different situation than, say biceps, for which each head has a single nerve-if it is firing, the whole muscle is contracting. Think of rectus more like 6 or 7 muscles connected in series, any of which could (at least theoretically) contract on it's own. In reality, we don't have fine enough control to contract just 1 segment, but I don't have any trouble believing that the upper segments could be more active at a particular moment than the lower, or vice versa.

So when the title of the thread talks about "targeting different parts of the same muscle", this is unique for rectus abdominis, and can't be extended to muscles in general, or to any other single muscle, as far as I know. The only other possibilities that I can think of is some of the strap muscles of the lower back, but they don't show enough for anyone to worry about them.

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Our greatest fear should not be of failure, but of succeeding at things in life that don't really matter.--Francis Chan

It could also be that what the machine picks up, is which nerves are carrying the signal to contract, and not the contractions themselves.

The question for me is: why are they separately innervated, and what about certain movements would stimulate one part over the other and vice versa

Not to mention if one is contracting harder, wouldnèt that stretch the other moreÉ