Platysma display

How it works

The platysma is a broad, thin sheet of muscle that lies just under the skin of the neck. It starts on the upper chest and shoulders, runs up over the collarbones and the front of the neck, and attaches to the jaw and the lower face¹. It is a muscle of facial expression, and the facial nerve controls it².

When it contracts, it pulls the corners of the mouth down and lifts the skin of the neck. It fires during expressions of sadness and fright, and when you clench your teeth¹. Because it is so thin and so close to the surface, a hard contraction makes its fibres stand out as vertical cords running from the jaw to the collarbone.

People often call these cords neck tendons. They are not. They are the muscle bands themselves. The thick rope that runs from behind the ear to the breastbone is a different muscle, the sternocleidomastoid, and it stands out when you turn your head.

Most people can make the platysma fire as part of a grimace. Making it fire on its own, with a calm face, is a trained skill. Bodybuilders practise it because it makes the neck look defined in a pose.

How common it is

No study has counted how many people can flex the platysma on its own. What has been measured is the muscle, not the skill. A 2024 ultrasound study imaged 80 platysma muscles in 40 volunteers while they showed their lower teeth as hard as they could. It measured how the muscle thickened and slid as it contracted³. So the muscle answers in ordinary people. Flexing it alone, with a still face, is practised mostly in bodybuilding and posing circles, and nobody has surveyed how many can manage it.

Try it

1. Stand in front of a mirror with your neck bare.
2. Pull the corners of your mouth down and out as hard as you can, as if making a disgusted face.
3. Watch your neck. Vertical cords should appear from the jaw to the collarbone.
4. Relax your face. Now try to tense the neck alone, without the grimace. Keep your mouth still.
5. Practise for a minute a day.

Is it a problem?

No. Tensing the platysma is a normal muscle action, and it is not known to cause harm. The cords people see are muscle, not bulging tendons or blood vessels, so there is nothing to worry about in their appearance.

Mention it to a doctor only if a cord-like band in the neck:

• appears without you tensing anything,
• stays hard at rest,
• comes with pain.

That is a different finding from a voluntary flex.