Harriman D G
Department of Pathology (Neuropathology), University of Leeds, England.
Muscle Nerve. 1996 Nov;19(11):1447-56. doi: 10.1002/(SICI)1097-4598(199611)19:11<1447::AID-MUS9>3.0.CO;2-C.
There are two types of hypertrophy of the muscles of mastication in man: reactive hypertrophy, the more common form; and nonreactive enlargements-myositic, genetic, myopathic, and idiopathic. Reactive hypertrophy develops when the masticatory muscle workload is increased by local bone and dental disorders; such triggers are not powerful but act over long periods, thus demanding increased endurance. Exercise for endurance has a greater effect on the muscles of mastication than it has on the large muscles of the limbs; these react solely by stimulating the oxidative metabolism of type 1 fibers, whereas masticatory muscle reacts structurally by hypertrophy and progressive type 1 fiber predominance. Eventually enzyme instability of type 1 fibers and end stage atrophy of type 2 fibers may appear. Unexpectedly, lesions have also been found in control masticatory muscle, in particular type 2 fiber specific atrophy like that seen in long-standing acquired autoimmune myasthenia gravis. It is suggested that the adverse lesions in hypertrophied and control masticatory muscle are the consequence of post-activation fatigue.
反应性肥大，较为常见；以及非反应性增大——肌炎型、遗传型、肌病型和特发性。当咀嚼肌工作量因局部骨骼和牙齿疾病而增加时，就会出现反应性肥大；这些触发因素虽不强，但作用时间长，因此需要增强耐力。耐力锻炼对咀嚼肌的影响比对四肢大肌肉的影响更大；四肢大肌肉仅通过刺激1型纤维的氧化代谢做出反应，而咀嚼肌则通过肥大和1型纤维逐渐占优势做出结构上的反应。最终可能会出现1型纤维的酶不稳定和2型纤维的终末期萎缩。出乎意料的是，在对照咀嚼肌中也发现了病变，特别是类似于长期获得性自身免疫性重症肌无力中所见的2型纤维特异性萎缩。有人认为，肥大咀嚼肌和对照咀嚼肌中的不良病变是激活后疲劳的结果。
