You hear it all the time…”Keep your shoulders back! Stand tall! Chest out!” Posture has become an ever present issue within healthcare circles and your ergonomic-minded co-workers alike, but why exactly is posture so important? As renowned Doctor of Science Vladimir Janda explains,
“Human movement and function requires a balance of muscle length and strength between opposing muscles surrounding a joint.”
Poor posture results in what is known as a muscle imbalance at a joint, in which opposing muscles (the agonist and the antagonist) on opposite sides of a joint provide differing amounts of tension, due to muscle weakness or tightness. Muscle imbalances can then result in abnormal stresses applied to the joint.
While a muscle imbalance might not directly be a source of pain, many musculoskeletal pain syndromes are a result of chronic muscle imbalances. One musculoskeletal pain syndrome often diagnosed within the medical community is called upper cross syndrome.
Upper cross syndrome is characterized by forward head posture, increased thoracic kyphosis (rounded back), excessive mid-upper cervical spine extension, and scapular protraction (forward shoulders).
This results in tight upper cervical extensors and anterior thoracic muscles, as well as weakened (elongated) deep neck flexors and scapular muscles.
Tight muscles can impact joint movements in a variety of ways, most notability by biasing a joint to move in a certain direction due to hypertonicity, or increased muscle tone. Furthermore, tight muscles further exacerbate any poor postural tendencies or positions, as our muscles tend to adapt to a consistently shortened position. Conversely, elongated muscles become weak when they are lengthened past their optimal length. Every muscle has an optimal length in which it can produce the most tension (force). The amount of crossbridging between the myosin (thick) and actin (thin) filaments is directly correlated with the amount of tension the muscle can produce. Therefore, an elongated muscle does not have as much overlap between myosin and actin filaments so it cannot produce as much active muscle force. Overtime, these muscle imbalances of tight and weak muscles can lead to abnormal movement patterns, movement dysfunctions, and ultimately predispose your body to a host of other potential issues.
Some of the more common orthopedic issues that can potentially arise due to poor posture include cervicogenic headaches, generalized cervical neck pain, thoracic outlet syndrome, limited shoulder range of motion, and shoulder impingement.
Cervicogenic headaches are a special subclass of headaches that are referred from either bony structures or soft tissues of the neck. They are mechanical in nature and influenced by head and neck positions throughout daily activities. The upper and mid cervical extension characteristic of upper cross syndrome cause many posterior muscles, specifically the sub-occipital muscles, to become tight. Tightness of the suboccipitals can cause local irritation to upper cervical sensory fibers, which are believed to interact with the descending tract of the trigeminal nerve. This explains why dysfunctions of the neck can refer pain to the head and cause cervicogenic headaches.
Additionally, a study by Chiu et al (2005) found that patients with chronic, insidious neck pain responded extremely well to an exercise program that included deep neck flexor strengthening. The deep anterior neck flexors are one of the many muscles that are held at an elongated position with poor posture in upper cross syndrome. As discussed earlier, these elongated muscles are weak (and/or have impaired recruitment), and therefore can lead to muscle imbalances at the joints of the cervical spine, effect static and dynamic stability, and movement coordination. Additionally, this forward head posture increases the amount of load applied to your cervical vertebral. This can place unnecessary stresses on the spine and develop into a possible source of pain.
While poor posture might not directly be a source of pain, it represents a ‘mis-alignment’ of the body and can thus be a contributor to a host of neuromusculoskeletal conditions. Obtaining correct posture is easy. A physical therapist will be able to help you strengthen elongated muscles and stretch shortened muscles; however, once you have the adequate strength and muscle length, it’s up to you to remember to maintain this ideal posture throughout the day. Try to constantly remind yourself, if you’re sitting, standing, or walking around, to “stand tall, keep that chest out, shoulders back, and head relaxed!”