Same muscle, different functions

Picture two pull ups.

It’s using the same nunchuck handles. But one grip is 32 inches apart. The other is 20 inches apart.

What’s the big deal? A pull up is a pull up.

Well. Yes a pull up involves your scapula gliding and retracting, protracting and elevating and depressing. It’s the elbow bending and straightening. It’s the shoulder joint rotating and adducting.

It’s a complex exercise with many moving parts.

And when there are many moving parts, many muscles around those moving parts get involved.

So in case of the pull up, the muscles that are involved in producing that particular movement the lats, traps, biceps, rhomboids and many muscles around the rotator cuff. Many more are involved too. But let’s keep this simple.

You’ll notice on the wider grip, the arm bends less. The shoulder is more rolled back. The scapula glides more than it pulls back (retracts). There’s more adduction. All these produce a require the same muscles: lats, biceps, rotator cuff, traps, rhomboids to work ‘differently’. Simply put, the same muscles work in different ways. The science behind this is gnarly:

Every muscle has a starting point and finishing point (origin and insertion). These points are on bones. When you move, these bones and the joints move. And the movement is three-dimensional.

And every relative position that involves less of the arm bending, more of the scapula squeezing together or gliding down or shrugging up produces a distinct position that twists and lengthens the muscle in a slightly different direction.

And for the muscle these distinct positions produced by the bones and joints mean the kind of work they are doing is specific, different and distinct.

Which is why if you’ve been doing chin ups for a while, a pull up feels different and more challenging. If you’ve been doing pull ups like a chin up with elbows bending more, scapula gliding less and shoulders adducting less dramatically (elbows closer to armpit), doing the opposite ( a strict pull up) can feel quite challenging. That’s how specific adaptations or muscles change in response to performing an exercise in a specific manner.

There is some transfer. You can do one or a few stricter pull ups if you can do 10-12 chin ups.

But to be able to do a strict pull up, you train it. Systematically.

The same applies for different grips. Different camber angles of the pull up bar. Even deadlifts. Trapbars are different from barbells that are different from t-bells. Again, there are distinct positions each gadget needs to be lifted effectively. Spine, knees, hips and ankles are in slightly different degrees or bending, straightening and rotation. This results in the quads, hamstrings, glutes and other muscles working in different ways.

You get the point. Hopefully. This is hard to visualise. It’s my first stab at explaining it. I hope to get better at it!

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