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Significance of Group III and IV muscle afferents for the endurance exercising human
Author(s) -
Amann Markus
Publication year - 2012
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2012.05681.x
Subject(s) - skeletal muscle , reflex , muscle fatigue , central nervous system , muscle contraction , medicine , afferent , endocrinology , neuroscience , anatomy , chemistry , biology , electromyography , physical medicine and rehabilitation
Summary With the onset of dynamic whole‐body exercise, contraction‐induced mechanical and biochemical stimuli within locomotor muscle cause an increase in the discharge frequency of thinly myelinated (Group III ) and unmyelinated (Group IV ) nerve fibres located within the muscle. These thin fibre muscle afferents project to various sites within the central nervous system and thereby substantially influence the exercising human. First, Group III / IV muscle afferents are the afferent arm of cardiovascular and ventilatory reflex responses that are mediated in the nucleus tractus solitarius and the ventrolateral medulla. Therefore, neural feedback from working skeletal muscle is a vital component in providing a high capacity for endurance exercise because muscle perfusion and O 2 delivery determine the fatigability of skeletal muscle. Second, Group III / IV muscle afferents facilitate ‘central fatigue’ (failure, or unwillingness, of the central nervous system to ‘drive’ motoneurons) by exerting inhibitory influences on central motor drive during exercise. Thus, Group III / IV muscle afferents play a substantial role in a human's susceptibility to fatigue and capacity for endurance exercise.