Brown M, Ross T P, Holloszy J O
Program in Physical Therapy, Washington University School of Medicine, St. Louis, Missouri 63110.
Mech Ageing Dev. 1992 Mar 15;63(1):69-77. doi: 10.1016/0047-6374(92)90017-8.
The effects of ageing and of exercise on muscle mass, fiber cross-sectional area, and fiber type composition of a weight-bearing muscle, the soleus and a non-weight-bearing muscle, the extensor digitorum longus (EDL) were investigated in female Long-Evans rats. The animals were exercised by means of voluntary wheel running beginning at 4 months. Runners and sedentary controls were studied at 9 months and 27 months of age. In sedentary rats, the soleus muscle weighed 26% less, and the EDL weighed 19% less at age 27 months, than at 9 months. This decline in muscle mass was accounted for by a similar decrease in muscle fiber cross-sectional area. The wheel running resulted in significant hypertrophy of the soleus in both 9- and 27-month-old rats; as a consequence the 27-month-old runners had larger soleus muscles than the 9-month-old sedentary rats. The running did not prevent atrophy of the EDL in the old rats, but did increase the proportion of type IIa fibers. The exercise also increased the number of capillaries per fiber in the soleus muscles of both young and old rats. In conclusion, the finding that wheel running prevented atrophy with ageing of the weight-bearing soleus but not of the non-weight-bearing EDL emphasizes the specificity of exercise, and shows that exercise-induced muscle hypertrophy can be maintained in old age by appropriate exercise.
在雌性Long-Evans大鼠中，研究了衰老和运动对负重肌肉比目鱼肌以及非负重肌肉趾长伸肌（EDL）的肌肉质量、纤维横截面积和纤维类型组成的影响。从4个月大开始，通过自愿轮转跑步的方式让动物进行运动。对9个月和27个月大的跑步组和久坐对照组进行了研究。在久坐的大鼠中，27个月大时比目鱼肌的重量比9个月大时减少了26%，EDL的重量减少了19%。肌肉质量的这种下降是由肌肉纤维横截面积的类似减少所导致的。轮转跑步导致9个月和27个月大的大鼠比目鱼肌显著肥大；因此，27个月大的跑步组大鼠的比目鱼肌比9个月大的久坐大鼠更大。跑步并不能防止老年大鼠EDL萎缩，但确实增加了IIa型纤维的比例。运动还增加了年轻和老年大鼠比目鱼肌中每根纤维的毛细血管数量。总之，轮转跑步可防止负重的比目鱼肌随衰老而萎缩，但不能防止非负重的EDL萎缩，这一发现强调了运动的特异性，并表明通过适当运动，运动诱导的肌肉肥大在老年时可以维持。
