usually peaks when race-day arrives. However, once the athlete has met their goal, the endorphin levels can suddenly drop, causing an isolated mus-cular weakness referred to as “motor muscle inhibition.” Because most ath-letes engage in activity recreationally, rather than professionally, they too can run into the problem of overtraining. What is happening? Since there is a lack of a causal rela-tionship between diagnostic imaging results, orthopedic testing and symp-toms, we must look further into what is happening on a musculoskeletal level when patients who overtrain experi-ence pain and dysfunction. Motor muscle inhibition: Muscle motor inhibition (alpha-motor neuron muscle inhibition) is when the nerve that sends the impulse to contract a muscle becomes unable to function at its optimal capacity due to chemical or physical trauma. This results in a per-ceived weakness of that muscle, which changes the biomechanics of the entire region. The primary cause of motor inhibition is neurogenic inflammation, in which inflammatory, noxious sub-stances are released by the sensory axon to inhibit the motor neuron. Neurogenic inflammation: Neu-rogenic inflammation is continuing inflammation in the musculoskeletal system generated by nerve impulses and the release of inflammatory sub-stances from the sensory axon at the site of the original injury. These sub-stances typically include but are not limited to, substance P, calcitonin gene-related peptide (CGRP) and neurokinin A. Prolonged inflammation and pain can lead to protective muscle spasm, accumulation of fibrous tissue and muscle shortening. The fibrous tissue forms palpable taut muscle bands and trigger points; such muscle dysfunction and spasm lead to compression of blood vessels and decreased blood flow, creating nociception. In short, nociception is the nervous system’s reaction to irritating chemicals. Neu-rogenic inflammation, which can be caused by injury or repetitive strain. This causes that muscle to become inhibited. Chronic nociceptive stimuli result in a cortical delay of the motor output and reduced activity of the painful muscle, which can prevent ef-fective motor retraining. In short, overtraining can trigger motor inhibi-tion and continued training can cause more tissue damage. In less than 24 hours: Ryan ran four marathons. He did it in temperatures that averaged less than 5 degrees Cel-sius over the period. He ran through the night in the frigid cold with only three to four 25-minute treatment breaks. A feat nearly super-human, but ultimately not immune to the potential long-term effects of overtraining. As physicians we must be aware of these pitfalls and we must educate our pa-tients so that they reduce long-term injury. www.Cndoctor.ca CND_ContemporaryAcupuncture_NovDec21_CSA.indd 1 November/December 2021 Chiropractic and Naturopathic Doctor 11 2021-11-10 11:02 AM
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