Trigger
points are felt as small, tender nodules and painful bands in skeletal
muscles. These knots are hyperirritable spots. When muscles work in an
eccentric fashion, that is a contraction occurs while the muscle
lengthens, damage occurs within the muscle cells. The reason why these
trigger points develop is because a neurotransmitter, Acetylcholine, is
released in excess, which then causes a persistent, localized muscle
contraction. This muscle contraction compresses blood capillaries which
then reduces blood flow. Lower amounts of oxygen and glucose is then
delivered to the muscle and an energy crisis is created. As a result, a
number of pain sensitizing substances are released which activate nerve
receptors that respond to pain. The muscle is unlikely to relax and
thus, a vicious cycle is created.
The
presence of a local twitch response, referred pain or reproduction of
symptomatic pain increases the certainty that a trigger point is
present. A local twitch response may occur when a trigger point is
stimulated with a needle. The response is a spinal reflex and is unique
to trigger points.
Trigger
points are classified as either active or latent. With active trigger
points, there are spontaneous complaints of pain locally or referred,
which may be present at rest or during movement. A latent trigger point
does not cause pain without being stimulated.
The
onset of trigger points can be related to acute, chronic or repetitive
muscle overload. A couple of pain problems where trigger points are
identified include radiculopathies, joint dysfunction, disc pathology,
tendonitis, craniomandibular dysfunction, migraines, tension type
headaches, carpal tunnel syndrome, computer related disorders, whiplash,
spinal dysfunction and pelvic pain and other urologic syndromes.
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