The Triceps “Shout”: When the Pain Isn’t Really the Triceps

Paulius Jurasius
Jan 30
3 min read

You know that moment: someone with rounded shoulders and a forward head tries to externally rotate the shoulder or horizontally abduct (that “open the chest / pull the arm back” motion) — and the back of the arm suddenly shouts.

Not a polite ache.

A sharp, radiating, why-is-my-triceps-angry-at-me kind of pain.

And this is where I often tell people:

“That pain is real — but it may be coming from elsewhere.”

First: what the triceps actually is

The triceps has three heads:

Long head (the special one): starts on the shoulder blade (infraglenoid tubercle) and crosses the shoulder joint
Lateral head: upper back of the humerus
Medial head: deeper, lower humerus

All three merge into one tendon to straighten the elbow — but the long head is the reason triceps can get dragged into shoulder drama. It’s not just an elbow muscle. It’s a shoulder-by-association muscle.

It’s also closely linked to the radial nerve territory (the nerve supply of triceps), which matters a lot for that “radiating” quality.

Why it screams during external rotation or horizontal abduction

With rounded shoulders / forward head, the upper body is usually living in a “collapsed-forward” geometry:

shoulder blades sit protracted, often tilted forward
front tissues (pec minor/anterior shoulder) tend to hold a protective tone
the humeral head doesn’t glide as cleanly in the socket
the neck and upper thoracic spine often contribute extra tension to the whole chain

Now try to externally rotate or pull the arm back. You’re asking the system to do the opposite of its habitual shape — like asking a folded umbrella to open while someone is still squeezing it.

That painful “triceps” shout usually comes from one (or a mix) of these sources:

1) The long head gets put on stretch + compression at the wrong time

Because it crosses the shoulder, external rotation + horizontal abduction can tension the long head.

If the shoulder mechanics are off (scapula not setting, humeral head not centred), the long head becomes a tension cable trying to stabilise a joint that isn’t organising itself well.

Result: the long head feels like the culprit, but it’s often the overworked assistant.

2) Trigger points in triceps can refer pain down the arm

Triceps trigger points — especially in the long head — can produce pain that feels deeper and more “radiating” than you’d expect from a simple muscle strain.

It can mimic nerve pain without being a “nerve injury” in the dramatic sense.

3) Neural tension gets invited to the party (radial nerve / C7-ish patterns)

This is the big one for that “radiating from elsewhere” quality.

In forward-head + rounded-shoulder posture, the nervous system is often already under subtle tension: neck position, collarbone area, shoulder girdle alignment.

When you externally rotate and abduct, you can add a nerve-tension component, and the brain interprets it as danger — sometimes projecting the sensation into the triceps region.

That’s why the pain can feel like it travels — because the nervous system doesn’t always give pain a neat postcode.

4) The scapula is late, so the triceps pays the bill

In a well-organised shoulder, the scapula rotates and positions early.

In the rounded-shoulder body, the scapula often arrives late to the movement — and then smaller tissues try to compensate: posterior cuff, long head triceps, even the back of deltoid.

So the triceps becomes the place where the system complains:

“We are trying to open a door with the hinges out of place.”

A simple way I explain it in the clinic

The triceps pain is often not the main problem.

It’s the alarm cable.

You pull the arm into a position the body doesn’t trust yet, and the alarm cable gets yanked. The nervous system responds fast and loud because that’s its job.

And interestingly, when posture and shoulder mechanics improve even slightly — when the shoulder blade is supported, when the neck stops reaching forward — that same movement often becomes less dramatic.

Not because the triceps was “fixed”.

Because the whole system stopped arguing with itself.