Have you heard of the term Trigger Point? Occasionally clients come in and ask questions about trigger points, like “what are they?” and “how do they form?” Many people have heard of the term, but they aren’t quite sure what they are. Well, trigger points are palpable nodules or knots no bigger than the size of a pea in the belly of a muscle. They are hypothesized to be “taut bands” that have specific referred pain patterns. It’s basically a section of over-‐contracted muscle fibers that cause the nodule to form. Interestingly, the nodules are not always painful, and as such they are termed latent trigger points. However they are still palpable nodules nonetheless. Not until they reproduce the referred pain of a client’s main or secondary complaint with mechanical pressure do we get concerned about them.
Identifying a trigger point in a muscle and observing the referred pain pattern on mechanical stimulation helps assist in making the proper determination if a nodule is in fact a trigger point. The mapping of trigger points is well documented and the exact patterns of referred pain are predictable as seen in the picture below. The “X” denotes the trigger point and the color represents the referred pain pattern from that trigger point. This picture is just a sample of the complex and vast number of documented trigger points and their associated referred pain patterns.
Through experience, I have found that there is a relationship between vertebral dysfunction and trigger points. Many times a trigger point will disappear when the corresponding vertebral segment is treated correctly. When treatment comes in the form of a manual medicine technique such as addressing a restricted joint dysfunction or hyper-‐ mobility then resolution of the trigger point usually follows. However, sometimes the trigger point does not respond. If the trigger point still persists after treating the corresponding vertebral segment, then the trigger point should be addressed individually. Conversely, when addressing the trigger point without first treating the vertebral segment, the vertebral and referred pain symptoms will only sometimes subside.
There is one more caveat about trigger points that is important to know. You should understand the difference between tonic and phasic muscles. Tonic muscles are ones that are more responsible for maintaining and contributing to your static postures such as sitting and standing. Phasic muscles create dynamic movement in space such as during walking or squatting. See below for a list of tonic and phasic muscles.
|Tonic (Postural) Muscles
Less prone to trigger points (partial listing)
|Phasic (Dynamic) Muscles
Prone to developing trigger points (partial listing)
|Pectoralis Major||Prone Scalenes|
|Upper Trapezius||Middle/Lower Trapezius|
|Levator Scapulae (exception)||Rhomboids|
|Quadratus lumborum (exception)||Abdominals|
When tonic muscles are not maintained properly they will naturally tighten up and shorten in length. The phasic muscles will do the opposite if left unattended; they will become neurologically inhibited and weak over time. Interestingly trigger points are more commonly found in phasic muscles rather than tonic muscles with the exception of the levator scapulae and quadratus lumborum. Knowing a muscles natural tendency gives us a clue to injury prevention. Also, when designing a therapeutic program it would be wise to stretch the tonic muscle groups to avoid muscle shortening. Conversely it is wise to “tone up” and strengthen the phasic muscle groups to avoid neural inhibition, weakness and also exacerbating trigger points.
In conclusion when you’re dealing with pain due to poor posture, short and/or weak muscles, or even referred pain; then evaluating trigger points in the corresponding soft tissue as well as evaluating the corresponding vertebral joint is critical for determining a long lasting treatment. Be sure to check with a physical therapist that is knowledgeable in trigger points and vertebral segmental dysfunction for the most comprehensive solution.