Ho K W, Roy R R, Tweedle C D, Heusner W W, Van Huss W D, Carrow R E
Am J Anat. 1980 Apr;157(4):433-40. doi: 10.1002/aja.1001570410.
Adult male albino rats were assigned randomly to control (CON) and weight-lifting (WL) groups. The WL rats were subjected to a progressive weight-lifting program against high resistance for 8 weeks. During the last 2 weeks, each WL rat lifted a load equal to 130% of its body weight. The mean weight of the adductor longus muscle was significantly increased in the WL group ( p < 0.05). This increased muscle weight was shown to be due to an increase in the number of fibers per unit cross-sectional area ( p < 0.05), and the mean sizes of both fast-twitch oxidative glycolytic and slow-twitch oxidative fibers were significantly smaller in the WL rats than in the CON rats (p < 0.05). Light and electron microscopic examination showed that five out of eight WL rats exhibited longitudinally split muscle fibers, while only one CON rat had a few centrally placed nuclei. The splitting process appeared as either a "pinching-off" of a small segment from the parent fiber or an invagination of the sarcolemma deep into the muscle fiber in a plane parallel to the sarcomeres. There were preliminary indications that this work-induced fiber-splitting process may be a physiological adaptation of muscle to the stress of exercise.
成年雄性白化病大鼠被随机分为对照组（CON）和举重组（WL）。WL组大鼠接受了为期8周的针对高阻力的渐进式举重训练。在最后2周，每只WL组大鼠举起的负荷相当于其体重的130%。WL组内收长肌的平均重量显著增加（p<0.05）。这种肌肉重量的增加被证明是由于单位横截面积内纤维数量的增加（p<0.05），并且WL组大鼠中快肌氧化糖酵解纤维和慢肌氧化纤维的平均尺寸均显著小于CON组大鼠（p<0.05）。光镜和电镜检查显示，8只WL组大鼠中有5只出现了纵向分裂的肌纤维，而只有1只CON组大鼠有一些位于中央的细胞核。分裂过程表现为从母纤维上“掐下”一小段，或者肌膜在与肌节平行的平面内深入肌纤维形成内陷。有初步迹象表明，这种由运动引起的纤维分裂过程可能是肌肉对运动应激的一种生理适应。
