The Trunk

Found this interesting article on biomechanical inefficacies:

We talk glove arm and arm actions, lower half, head position but what connects the energy one creates from the lower half up through the arm is the positioning and timing of the trunk.

Late trunk rotation is known to be one of the main checkpoints. What I’ve been looking at is, when foot contact is made and the shoulders are closed, what positions are other parts in? Glove arm is still out front, not tucked yet. The arm is in a semi-cocked position. The hips are open, flexion in the front leg and the back heel is peeled and facing the sky.

Rotation of the trunk follows, with the arm driving into external rotation, the glove arm funneling back into the body (still remaining firm out front, though), followed by the forward movement of the trunk drastically flexing forward, and everything stabilizing into the stride leg.

I understand, rotation is supposed to happen late as I mentioned. I don’t know how to teach/cue forward flexion of the trunk. Should it just be a result of complete hip rotation and a “late launch” upper half, or is there dependent qualities that need to be stressed?

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Oh wow, great find on this study! Let me read it a little more before replying, but thank you for posting it.

Is there a date for this article? Also, one point I disagree with is wrist flexion. I believe the wrist is straight at ball release. Flexion happens after release.

Regarding hip rotation, at foot contact I prefer hips to be open only as much as is necessary for front leg/foot to open up into foot plant. To me, the remainder of hip rotation should occur as/after the front leg braces.

As for trunk flexion, I wouldn’t try to teach/cue it because (1) it’s too late in the delivery - it’s much easier to teach that which happens early in the delivery, and (2) trunk flexion is set up by coming out of trunk rotation into a momentary isometric hold in a stacked poisition (low back arched/extended with head and upper spine upright) which is largely a strength and flexibility issue. From a mechanical standpoint, poor mechanics earlier in the delivery can cause early trunk flexion so it’s a matter of not doing those things wrong.


Isn’t the wrist actually in a layback position? It’s definitely not flexed just yet, but I don’t think it’s even straight either.