Why does my arm go numb when I reach overhead? Thoracic outlet syndrome considerations.

As you would probably intuitively guess, many sports have typical patterns of injury. For example, distance runners commonly complain of plantar fascia, achilles tendon and hamstring strains, while basketball players tend toward patellar tendinopathy (jumpers knee) and lateral ankle sprains.


For athletes in sports with a lot of overhead action, like racquet sports athletes, baseball pitchers and volleyball players, a common complaint is neck, shoulder and arm dysfunction characterised by weakness and sensory changes (numb/tingle or burning/electric pain). This dysfunction is typically aggravated by repeated  overhead swinging/throwing type action and can be quite debilitating when irritated.

This dysfunction, known as Thoracic Outlet Syndrome (TOS) is caused by a compression of a nerve bundle called the brachial plexus in a region of the neck and chest that includes a few key muscles as well as the clavicle (collarbone), shoulderblade and the first (uppermost) rib. In rarer cases, important arteries and veins that supply the arm can also be compressed.


See fig 1. Below for a visualisation of the anatomic structures involved. I drew that myself so I hope you spend some time enjoying it!

TOS can onset from a traumatic incident or from repeated stress. Some people are predisposed to the problem because of anatomical abnormalities like an extra rib at bottommost neck vertebra, or fibrous/scar bands that clamp down on the aforementioned nerves, arteries and veins.

Posture is also very important, and those of us with slumpy, slouchy posture  and winging shoulderblades are particularly at risk – as if we needed yet another reason to work on our posture!

As shown if figure 1 below, there are 3 suspect sites  for compression of the nerve bundles and blood vessels. Feel free to skip this section if the minutae of the anatomy is too mind numbingly dry for you!

  1. The interscalene triangle – Between the anterior and middle scalene muscles. Excessive growth of tightness of these muscles can compress the blood vessels and nerves.
  2. The intercostal space – the space between the 1st (uppermost) rib and the collarbone. An excessively large or tight subclavius muscle can add to the compression.
  3. The retro-pectoralis minor space – Behind to the pec minor muscle and tendon. As you can see the entirety of the brachial plexus nerve bundle as well as the subclavian blood vessels can become compressed between a thickened or tight pec minor muscle/tendon. Poor posture (slouched shoulders, caved in chest) can really contribute to compression issues here.

The Thoracic Outlet

Fig 1 – The thoracic outlet with interscalene triangle, intercostal space and retro-pectoralis minor space shown.

As you can see from  fig 1, there are a variety of ways and locations where the nerves and blood vessels can become compressed in the thoracic outlet.

The weakness and numbness that characterise the brachial plexus compressions are a pain in the butt but are also manageable and should resolve with treatment. This scenario represents 90+% of TOS cases.

In 1-5% of cases symptoms are driven by compression of those blood vessels (the subclavian artery and vein). These cases are characterised by some unique symptoms  including notable swelling in the arm and hand, cyanosis (blue discoloration) or pallor (paleness) of the arm, and pain that onsets consistently with activity. These cases should be checked out medically as there is the potential for more significant complication including clotting and in a worst case scenario, embolisms – clots that break free and travel to the lungs or brain where they can cause serious problems.

Ok, so we get that there is a problem. Wonderful. So what should we do about it?

Thankfully there are a number of very solid avenues to treat this issue, all of which help to decompress the vessels and nerves in the thoracic outlet. Most of these treatments are things that you can practice easily at home or in the gym. Even better right?

The approach is deceptively simple. A combination correcting posture, stretching tightened muscles, strengthening weak muscles and sprinkled over with a little bit of hands on manual therapy from a physiotherapist or muscle release by a massage therapist goes a long way!

Let’s have a look at some key pieces of these approaches!



Dysfunctional posture is corrected by mindful attention to positioning, and the practice of specific exercises.

The goal of posture correction exercises is to correct poor shoulderblade positioning common to TOS patients. The positioning errors are typically (but not always) depression, down-rotation and anterior tilting (see fig 2).

Thoracic outlket syndrome, typical posture fault

Fig 2. Depressed, down rotated and tilted shoulder blade on the right. Exercises aim to correct these positioning errors.

Start working on this problem with a scapular setting exercise. Most (but not all) cases will respond well to a procedure as follows:

  1. Tuck in the bottom tip of the shoulderblade – Imagine that you are trying to tilt the bottom tip of your shoulder blade  into your body. This is typically asociated with a lifting of the chest (“tall chest” as they might say in yoga circles).
  2. Tuck in the ribs –  You may notice after you have tucked in your shoulder blade that you have flared out your ribs and arched your low back. Correct this by contracting the abdominals to return the spine to a neutral position. Do not lose the shoulder blade tuck from (1) as you do this.
  3. Ensure you are “centered” – you should feel like your shoulder is in a centered position. This means that you still have room to retract, elevate, or depress your shoulders should you want. Your shoulder is not hanging out at the end-of-range in any direction.

Once you have mastered setting the shoulderblade in a resting position with your arm at your side you can begin to practice this exercise in increasing degrees of  arm elevation. First at 30, then 45, and finally 90 degrees and higher (overhead positions). See the video above for examples.

Once you have mastered setting the shoulderblade in overhead positions, begin practicing while lifting mild to moderate weights from arm at side through to overhead positions.


Other posture related factors

Consider addressing other factors that may contribute to poor posture.

An important low hanging fruit might include proper desk ergonomics. Do you have a good chair and do you know how to use it properly? Are your keyboard and mouse properly positioned?

Perhaps there are repeated daily activities that are unique to your life situation you can modify or improve. Let’s say you travel a lot and have to lift bags into overhead bins. In this case training  good lifting technique can be very helpful.

For larger chested women, proper bra fitting can also be very useful and there are specialty stores that can help to adjust your sizing and fit which is surprisingly helpful in the effort toward good posture.


Relief positions

Here’s a neat trick! You can also unload the tension in the thoracic outlet by supporting the shoulders in a way that slackens the pecs and scalene muscles. One easy to achieve method is to sit with the elbows flexed at 90 degrees and elevated slightly on two pillows (See Fig 3).

This position can be used while at a computer, reading or watching TV.

This is useful trick but remember, it’s a symptom management technique that provides temporary relief but is not a long term “cure”.

Thoracic Outlet Syndrome relief position

Fig 3. Use of the a slackening relief position as a symptom management technique.



Stretching the key muscles that when tight and tensioned can compress the nerve bundles or blood vessels seems so obvious as to be too silly to mention. But the obvious is often ignored, so lets not do that!

Stretch your scelene muscles by placing the hand of the affected side in your back pocket and side bending your head away toward the opposite shoulder. Hold at 4/10 intensity.

You can stretch your pecs by laying on the ground with your arm in an abducted position (see fig 4) and a light weight in your hand. Again you should feel a mild to moderate instensity (4/10 stretch sensation).

middle scalene stretch

Fig 4 – Scalene muscle stretch on the Left and pec stretch (top view, you would be laying on the ground) on the right.

As with any stretch the key here is not olympic medal winning intensity! Stretching is all about time under tension. Go for a mild stretch sensation and hold it for at least a minute – gold stars for you if you hit 2 minutes!



Taping to promote elevation, up-rotation and posterior tilting of the scapula may be helpful. You physiotherapist can help you to determine if this is a useful treatment for you and apply a tape job as needed.

Thoracic outlet Syndrome tape

Fig 5. Tape promotes up-rotation and elevation to support a normal scapular position. This may unload the compression of the neurovascular bundle


Take home thoughts

So you can see that the protocol to deal with TOS is simple. But as I often say, just because something is simple does not make it easy!. Practicing posture, for example, over a period of months takes dedication and discipline.

The resolution of TOS symptoms does not occur overnight. Expect noticeable improvement in 2-4 weeks but it can take several months for symptoms to fully resolve. Stay the course!

If you are unsure about the nature or progress of your symptoms you should without question speak with your physiotherapist to have your specific situation properly evaluated.

In the meantime though try some of the things suggested here, especially the posture correction!. At the very least have fun trying. Worst case scenario you’ll look a lot better for your improved posture!


Further reading (when you really want to impress your friends)

Ferrante, M. A., & Ferrante, N. D. (2017a). The thoracic outlet syndromes: Part 1. Overview of the thoracic outlet syndromes and review of true neurogenic thoracic outlet syndrome. Muscle & nerve, 55(6), 782-793.

Ferrante, M. A., & Ferrante, N. D. (2017b). The thoracic outlet syndromes: Part 2. The arterial, venous, neurovascular, and disputed thoracic outlet syndromes. Muscle & nerve, 56(4), 663-673.

Hooper, T. L., Denton, J., McGalliard, M. K., Brismée, J. M., & Sizer, P. S. (2010a). Thoracic outlet syndrome: a controversial clinical condition. Part 1: anatomy, and clinical examination/diagnosis. Journal of Manual & Manipulative Therapy, 18(2), 74-83.

Hooper, T. L., Denton, J., McGalliard, M. K., Brismée, J. M., & Sizer Jr, P. S. (2010b). Thoracic outlet syndrome: a controversial clinical condition. Part 2: non-surgical and surgical management. Journal of Manual & Manipulative Therapy, 18(3), 132-138.

Kuhn, J. E., Lebus, G. F., & Bible, J. E. (2015). Thoracic outlet syndrome. JAAOS-Journal of the American Academy of Orthopaedic Surgeons, 23(4), 222-232.

Levine, N., & Rigby, B. (2018, June). Thoracic Outlet Syndrome: Biomechanical and Exercise Considerations. In Healthcare (Vol. 6, No. 2, p. 68). Multidisciplinary Digital Publishing Institute.

Watson, L. A., Pizzari, T., & Balster, S. (2009). Thoracic outlet syndrome part 1: clinical manifestations, differentiation and treatment pathways. Manual therapy, 14(6), 586-595.

Watson, L. A., Pizzari, T., & Balster, S. (2010). Thoracic outlet syndrome part 2: conservative management of thoracic outlet. Manual therapy, 15(4), 305-314.

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