Vladimir Janda, MD, researched and studied the musculoskeletal system and created the two-category system to describe the work that muscles are suited to perform: tonic muscles (aka postural) and phasic muscles.
Postural muscles sustain our bodies and resist the power of gravity. They hold our body upright, our head in place, and allow us to stand for long periods without pain. They are composed of slow-twitch fibers and are suited for sustained work. Postural muscles can cause posture problems because they are functionally tight.
Phasic muscles are fast-twitch and suited for moving. They are for explosive movement and not prolonged usage. These are the muscles we use to exercise; traps, deltoids, quads, and so forth. They fatigue easily. Phasic muscles can cause posture problems because they are functionally weak.
Postural muscles shorten and tighten in overuse while phasic muscles lengthen and weaken. Problems arise when trauma-type situations and/or overuse occur because the muscles tend to try to compensate for each other, a scenario they were not designed to function well in. This crossing of functions leads to the creation of painful trigger points, imbalance, joint instability, over and under correction of posture, and thus to the generation and maintenance of pain.
“When muscles are out of balance, postural and movement anomalies occur . . . manifesting as pain in one or more of the affected structures.” — Wikipedia
The work of Vladimir Janda, MD,
forms the backbone of Structural Therapy.
Vladimir Janda, MD
Author on pain and musculoskeletal systems
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