Your traps, short for trapezius muscles, are a pair of large, flat muscles that span the back of your neck, across your shoulders, and down to the middle of your back. They’re one of the broadest muscles in your upper body, forming a diamond or kite shape when you look at both sides together. The trapezius plays a role in nearly every movement involving your shoulders, neck, and upper back, which is also why it’s one of the most common sites of tension and pain.
Where the Trapezius Sits
The trapezius starts at the base of your skull and runs all the way down to the middle of your spine, roughly at the level of your lowest ribs. From there, the fibers fan outward to attach to your collarbone and shoulder blade. Because it covers so much territory, the muscle is divided into three distinct sections, each with its own job.
The upper traps are the fibers running from your skull and the back of your neck down to your collarbone and the top of your shoulder blade. These are the muscles you feel tighten when you’re stressed or hunching over a phone. The middle traps stretch horizontally from your upper spine out to your shoulder blade. The lower traps angle upward from the mid-spine to the inner edge of the shoulder blade. Together, the three sections give the muscle its characteristic diamond shape.
What Each Section Does
The upper traps are responsible for shrugging your shoulders upward and tilting your head to one side. Any time you hold a phone between your ear and shoulder or carry a heavy bag, your upper traps are doing most of the work. They also help rotate your shoulder blade upward when you raise your arm overhead.
The middle traps pull your shoulder blades together toward your spine. This is the squeezing motion you feel when you stand up tall and pinch your shoulders back. That retraction keeps your posture upright and stabilizes your shoulder blade against your ribcage during pushing and pulling movements.
The lower traps pull the shoulder blade downward and also assist with upward rotation. They counterbalance the upper traps: while the upper portion lifts the shoulder, the lower portion depresses it. This balance is critical for healthy shoulder mechanics, and when it breaks down, problems follow.
Why Trapezius Imbalance Causes Problems
Research consistently shows that people with shoulder pain during arm elevation tend to have overactive upper traps combined with underactive or delayed middle and lower traps. That imbalance creates abnormal shoulder blade movement, sometimes called scapular dyskinesis. In practical terms, your shoulder blade doesn’t glide smoothly along your ribcage the way it should. Instead, the overactive upper traps pull the collarbone up too much and tilt the shoulder blade forward, which can pinch structures in the shoulder joint.
If the trapezius becomes genuinely weak, such as from nerve damage, the entire shoulder girdle droops. The shoulder blade sags downward and forward while rotating in the wrong direction. Left untreated, this can destabilize both the shoulder joint and the joint where your collarbone meets your breastbone. Delayed activation of the middle traps, even without outright weakness, has been measured in people with shoulder pain and likely contributes to poor stabilization of the shoulder blade during arm movements.
Why Your Traps Are Always Tight
Computer workers have an annual neck and shoulder pain rate of 27 to 48 percent, significantly higher than workers in other occupations. The culprit is sustained, low-level muscle activity. You don’t need to lift heavy objects to overwork your traps. Holding your arms over a keyboard, looking down at a screen, or craning your neck forward all keep the upper trapezius under constant mild tension. Over time, that low-amplitude activity leads to overuse injuries.
About one in three office workers with chronic neck pain specifically have trapezius myalgia, a clinical term for persistent trapezius pain and tenderness. Women appear to be affected more often than men, possibly because they get fewer natural rest periods in their muscle activity patterns during desk work. The upper trapezius is also one of the most common muscles to develop trigger points: tight, hypersensitive knots that produce pain not just locally but in distant areas. Trigger points in the upper traps are known to refer pain up into the head, neck, and temple region, which means that nagging headache you get after a long workday may actually originate from your traps.
How the Muscle Is Controlled
The trapezius has a somewhat unusual nerve supply. Movement is controlled by the spinal accessory nerve, which is the eleventh cranial nerve running directly from the brainstem. This is different from most back and shoulder muscles, which are controlled by spinal nerves exiting the neck or upper back. Sensation in the trapezius, including pain and your sense of the muscle’s position in space, comes from cervical nerves at the C3 and C4 levels in your neck.
This split nerve supply matters because damage to the spinal accessory nerve, which can happen during certain neck surgeries or injuries, can paralyze the trapezius while leaving sensation intact. The result is a shoulder that droops and a shoulder blade that wings outward, with significant loss of arm function overhead.
Exercises That Target Each Section
Most people’s upper traps get plenty of stimulation from daily life and stress. The middle and lower traps, however, tend to be undertrained, which feeds into the imbalance pattern linked to shoulder pain. Choosing exercises that selectively activate the lower and middle portions can help correct this.
Research using muscle-activity sensors found that two exercises performed with the arms below shoulder height produced strong lower trapezius activation. The press-up (sitting with hands on a surface and pressing down to lift your body slightly) activated the lower traps at about 56 percent of maximum effort. Scapular retraction (squeezing your shoulder blades together) activated the lower traps at roughly 51 percent and the middle traps at about 50 percent of maximum effort.
For isolating the lower traps specifically, bilateral shoulder external rotation (rotating both arms outward against resistance while your elbows stay at your sides) produced the highest ratio of lower-to-upper trap activation of any exercise studied. The lower traps worked at more than double the rate of the upper traps during this movement, making it a useful choice when upper trap dominance is part of the problem. These exercises are particularly valuable because they don’t require raising the arms overhead, which can be painful for people already dealing with shoulder issues.
Signs of Trapezius Trouble
Trapezius-related pain typically shows up as a dull ache or tightness across the top of the shoulders and base of the neck, often worse on one side. It tends to build gradually through the day, especially with desk work, and may come with stiffness when turning your head. Trigger points in the upper traps can produce a characteristic pain pattern: a “ram’s horn” shape sweeping from the back of the neck up to the temple, which many people mistake for a tension headache.
If you notice one shoulder sitting higher than the other, difficulty keeping your shoulder blades flat against your back, or a visible winging of one shoulder blade, that may point to a trapezius imbalance or weakness worth addressing. Pain that shoots down the arm, numbness in the hand, or sudden weakness in the shoulder suggests a different problem and warrants professional evaluation.