Dumb question incoming. I know there the asymmetry in the shape of your abs (e.g., looks very staggered) are genetic, but what about asymmetry in size? The blocks on my right side are bigger (as in, protrudes out front more) than on the blocks on my left. Does that make sense? Is this also genetic? Is it a byproduct of being right handed (I used to play tennis a lot so I’m sure I did MANY more torque-y rotations in one direction than the other)?
Now that the question has entered my head, I’m more intellectually curious than seeking a “solution” for this non-problem per se.
Not a dumb question, and the answer’s more interesting than you’d expect.
The staggered look you’ve got right: the number and placement of the tendinous inscriptions that cut the rectus into “blocks” is genetic, and it’s rarely symmetric side to side. Size and protrusion asymmetry between the left and right columns is just as common and also mostly down to how you’re built.
The tennis part is interesting and supports your assertion. Unilateral rotation sports really do produce measurable ab asymmetry. There’s an MRI study on pro tennis players showing their rectus abdominis was about 35% bigger on one side, with the gap widening toward the lower abs. So your instinct that all those one-directional torque-y rotations did something isn’t crazy.
The twist is, in tennis players it’s the non-dominant side that ends up bigger. So much for that theory if you’re right handed…
Which points back to the boring answer: it’s most likely just genetic segment size and placement, maybe with a little help from rib cage and pelvis position or how you carry fat.
And as you already clocked, it’s a non-problem. You can hammer symmetrical ab work if you like, but it won’t rearrange genetic block placement, and nobody has ever lost sleep worth losing over which column of their six-pack sticks out an extra millimeter.
Further reading
We don’t have a BBM piece on this one, but since you’re curious, the actual study is a fun read: Large Asymmetric Hypertrophy of Rectus Abdominis Muscle in Professional Tennis Players (Sanchís-Moysi et al., PLOS One 2010). Large Asymmetric Hypertrophy of Rectus Abdominis Muscle in Professional Tennis Players
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Thank you for the detailed answer, and how fascinating that the hypertrophy is on the opposite side. I suppose it makes sense since there would be more contractile motion on opposing side now that I think about it.
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