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Thursday, December 20, 2012

Thoracic Outlet Syndrome (TOS) and Cycling

So, this blog is typically about plantar fasciitis, tibialis posterior tendonitis, running and walking mechanics, cycling, etc.  Since cycling is included in this blog, a reader recently wrote and suggested to blog about Thoracic Outlet Syndrome (also known as TOS) and the relevance it has to cycling.  I thought this to be an excellent suggestion!  For many of us, the cycling season will soon be upon us.  I know that here in Arizona the first official race is Sunday, January 20, 2012.  The first large stage race is the second weekend in February.  This event is the Valley of the Sun Stage Race.  So, if you are a seasoned cyclist or a novice intending to participate in racing this coming season, you’ve probably been committing yourself to spending time base training.  This type of training often keeps you in the saddle for long periods of time while performing more of a “spin” on the bike vs. riding hard for shorter periods of time.  The off season of cycling is also a good time to spend time in the gym conditioning your back, shoulders, arms, trunk, etc. in order to be more efficient on the bike and avoid overuse injuries in these areas during the early or mid part of the race season.

Many of you that are experienced riders whether you ride competitively, for fitness, or commuting are most likely experienced with a numbness that will creep up on you mid ride and present itself in your hand.  The area in your hand can either be the 4th and 5th fingers or the thumb, 2nd, and 3rd fingers.  This numbness typically originates from pressure in a specific part of your hand that is doing most of the weight bearing on the handlebars.  This is usually a benign type of nerve palsy or intermittent occlusion of blood flow into the hand.  The nerve that provides motor control and/or sensation will be compressed and subsequently cause the numbness.  A shift in weight or a change up in your grip on the handlebar usually resolves the numbness.  No problem right? It’s akin to moving your leg for the circulation to normalize when your foot goes to “sleep”.

Thoracic outlet syndrome also involves nerves and vessels.  However, TOS is a much more involved and more serious condition involving multiple structures at the neck and shoulder.  Before more is said about TOS, let me familiarize you with what TOS is and how one acquires TOS.

TOS is a disorder or group of disorders arising from compression on a neurovascular (nerves and vessels) bundle that supplies blood, motor, and sensory function from the neck to the shoulder, arm, and hand.  TOS symptoms can mimic the symptoms of a “pinched” nerve in cervical spine.  In some cases this is true due to the tension being applied on the neurovascular bundle down stream in the anterior neck, upper anterior chest, or shoulder.

Because cycling is a sport that requires a specific posture over a long period of time, the tissues involved in cycling are going to adapt to this posture.  So, lets say I’m on my bike riding for 2 - 4 hours per day or every other day preparing for race season.  The muscles in my neck, shoulders, upper chest, and arms are going to adapt to this position.  And it just so happens that this position is one in which is opportunative for the onset of TOS.  When on a road bike, you have a head forward and rounded shoulder posture.  This position allows the onset of abnormal tissue length tension in all of the suspect tissues and bony structures.  Just as in running and walking, muscles need to maintain a balance with each other.  If specific muscles in the neck and shoulder develop an abnormal length tension, then the brachial plexus can become compromised.  As a result, compression on the nerves and on the subclavicle and axillary artery occurs.  When only the blood supply is compromised, this can cause a global sensation of numbness, tingling, and weakness in the affected arm and hand like you would experience if your leg or foot are falling "asleep".  If the nerves that make up the brachial plexus are compromised in addition to the blood supply, then sensory and motor control in the upper extremity will be compromised.  It’s when the nerves become compromised that moderate to severe pain symptoms can become present.  When it comes to pain arising from an irritated nerve, pain symptoms take on various forms.  These forms can be a deep penetrating ache in the shoulder, the biceps, triceps and the forearm.  Burning may be present.  A stabbing and throbbing pain can be present in a constant mode or in an intermittent mode and will come and go depending upon the position of your head, neck, and shoulders as well as the position of your arms.  If it’s a case of nerve root compression, a very noticeable weakness in the involved shoulder and upper extremity will be present.

There are three specific areas in which the nerves can be irritated or compressed.  The first one is at the opening in your neck where the nerves exit.  This is called the intervertebral foramen This foramen can become smaller due to your neck being in an extended position.  A second contributor to the foramen narrowing is the abnormal tension on the muscles involved in maintaining proper alignment of the cervical vertebrae.  A third contributor to nerve compression is where the nerves pass under the clavicle and over the top of the first rib.  Again, when adjacent or involved tissues develop abnormal length tension, the space between the first rib and clavicle will reduce thus compressing the nerve bundle. 

Image 1 shows the nerves and their associated spine levels that make up the brachial plexus.  These nerves are the 5th cervical to the 1st thoracic.  The vessel in the brachial plexus is the axillary artery which is an extension of the subclavian artery.  These levels are seen between the red dots.

Image 1

Image 2 shows an anterior view of the brachial plexus as it exits the cervical spine and then passes under the clavicle and over the 1st rib.

Image 2
Image 3

Image 3 indicates the anterior scalene muscles.  As the nerves leave the foramen, they enter and then pass through the anterior scalene muscles.  These muscles are postural muscles.  They are very important in maintaining proper alignment of the cervical vertebrae.  These muscles are also responsible for specific motions at the cervical spine such as neck flexion, rotation, etc.  It is not uncommon for these muscles to become so taught that the scalene muscles themselves when palpated will feel like bone.  So when considering contributing factors to TOS, a bone pressing on a nerve can cause issues!

Image 4

Image 4 is showing how the pec minor muscle lies over the brachial plexus.  When the pec minor muscle is overdeveloped or presents with excess tension, a significant amount of compression can be applied to the brachial plexus.  The pec minor muscle originates in the anterior shoulder.  It is a muscle that makes up part of the shoulder girdle muscles (it is not part of the rotator cuff muscles).  The pec minor muscle then attaches to the 3rd – 5th ribs.  By now, you can likely deduce the effect that occurs if this muscle becomes very tight.  The ribs elevate causing compression on the plexus in the anterior shoulder and chest.  As with the anterior scalenes, the pec minor muscle can also become extremely bound up and tight that it presents with a very hard bone like feel when palpated.

Thoracic outlet syndrome isn’t something that suddenly occurs.  Just as with tibialis posterior tendonitis or plantar fasciitis, TOS comes on gradually and is usually the direct result of tissues tightening and shortening to a point at which they were not intended.  Just as I’ve blogged about before, it’s extremely important to maintain a balance between muscle groups.  In the case of TOS, the opposing muscles have become excessively lengthened and weak.  There is a term for this as well.  It’s simply referred to as “stretch weakness”.  To offset the symptoms of TOS, strengthen the opposing muscle groups and actively stretch the shortened muscles and self massage these muscles or have a massage performed by someone familiar with TOS.  In addition, if symptoms of TOS have been intermittently presenting, don’t ignore them.  Have a bike fit performed for proper posture during those long periods on your bike and get to a gym or just at your house and perform strengthening exercises to counteract the opportunistic events preceding TOS.

Happy Holidays and Happy Bipeding!

Brad Senska, PT, DPT, BS, ASTYM.

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