Thursday, December 29, 2011

Movement and Muscles at the Trunk

biggie flexes her trunk

What movements happen at this joint?

Flexion happens at the trunk when you pull your chest toward your thighs, decreasing the angle between the two parts. Or more simply, when you bend forward at the waist.

What muscles make these movements happen?

trunk flexion, lateral flexion, and rotation

The muscles that flex your trunk are your rectus abdominis, external obliques, internal obliques, and transverse abdominis, all anterior muscles that pull the chest forward when they contract.

What's more interesting about these abdominal muscles is how they're crisscrossed to hold in your guts and hold you up from superficial to deep: rectus abdominis is vertical, external oblique is diagonal pointing to your crotch, internal oblique is diagonal pointing to your butt, and transverse abdominis is horizontal. Also they produce different movements depending on how they are engaged, flexion engages them bilaterally so you bend straight forward.

What exercises make these muscles work?

Planks and any variations thereof (including pushups), situps and any variations thereof (including bicycles), pelvic tilts.

Transverse abdominis, the deepest of your abdominal muscles, is the muscle we're trying to get at when we imagine pulling our navels to our spines, if you've heard me say that eight million times. We sit so much in modern life, your brain may have forgotten the way to transverse abdominis. What it's supposed to do is stabilize your spine when you move your arms and legs. When you make your living hunting woolly mammoth, your brain is firing a hundred million signals at transverse abdominis on a daily basis. At your desk job, not so much. Thus this lower back pain, thus this getting knocked over. So start firing those signals again and find that muscle, because home season is coming up and woolly mammoth season is on.

When I was an intern in New York sort of like Sylvia Plath, I lived in a suite with five other girls and we talked about things like how to keep your stomach flat, and one of them said that her mother didn't work out, she just always sucked in her stomach wherever she went, and I thought to myself, That's dumb, that's not really having a flat stomach, that's just looking like you have a flat stomach. And I tell you this because there's times, like when I'm folded over my thighs and the bikram instructor is saying, "Suck in your stomach," and my eyes are perfectly level with my stomach literally hanging out like it hasn't done a day's work in its life, and I want to go back in time and hit myself in the face with a shovel. That could have been twenty-four years of sucking in my stomach i.e., strengthening transverse abdominis, you would be able to rock climb my abs by now.

Oh well the best time to plant an ab is twenty years ago, and the second best time is now. When the instructor says suck in your stomach, I suck up as much of my relaxed low belly as I can and think, of all the possible words from the future you're going with "suck in your stomach," okay then.