Objective To investigate the influence of exercise training on the exercise capacity ,the free radical content and the antioxidant enzyme activity in different muscle fibers in rats . Methods Male Sprague-Dawley rats were divided into three groups : sedentary, untrained and trained groups .The trained rats run on a treadmill (15～20 m/min ,60 min/d ,6 d/wk ) for 8 weeks and were subjected to the exericse test before and 24 h after exercise training . The untrained rats, used as the control of the trained group , moved freely within a cage except for being subjected to the exercise test at the corresponding time point . The sedentary rats moved freely within a cage without any intervention . 24 hours after exercise test the malondialdehyde (MDA) content, total antioxidant capacity (T-AOC)and superoxide diasmutase (SOD) activity were measured in three types of skeletal muscle fibers ( Ⅰ , Ⅱ a, Ⅱb). Results (1) Compared with the untrained group and before-exercise session, the maximal running distance and duration were significantly higher in the trained group (P<0.01). (2) MDA content of red muscle ( Ⅰ ,Ⅱa) was higher than that in white muscle (Ⅱb) whithin a control group (P<0.05). MDA levels of Ⅱa and Ⅱb fibers in the untrained group and of Ⅱb fiber alone in the trained group were higher than those of the sedentary group (P<0.05). (3) Compared with that of the control group , T-AOC of the Ⅰ and Ⅱa fibers in the trained group increased significantly , but had no difference in Ⅱb fiber. However, T-AOC of the Ⅱb fiber in the untrained rats was lower than that in control group (P<0.05). (4) Compared with that of the sedentary group, SOD activity of Ⅰ and Ⅱ a fibers in the trained group increased significantly, but had no difference in Ⅱ b fiber. SOD activity was unchanged in three types of fibers in the untrained group. Conclusion Exercise training selectively increases SOD activity and T-AOC in Ⅱ and Ⅱ a fibers and enhances free radical degradation , which is responsible for training-induced augmentation of the exercise capacity in the skeletal muscle .%目的 探讨运动训练对骨骼肌运动能力和不同类型肌纤维自由基代谢的影响.方法 雄性SD大鼠随机分为3组:安静组、非训练组和训练组.训练组大鼠进行8周跑台运动(15～20 m/min,60 min/d,每周6 d),在训练前及训练结束后24 h进行运动能力测试;非训练组除了在相同时间点进行运动能力测试外,其余时间笼内自由活动;安静组大鼠笼内自由活动,未进行任何干预.非训练组和训练组大鼠在运动测试结束后24 h检测3种不同类型(Ⅰ、Ⅱa、Ⅱb)骨骼肌肌纤维丙二醛(MDA)含量、总抗氧化能力(T-AOC)和超氧化物歧化酶(SOD)活性等.结果 (1)与非训练组和运动前比较,训练组最大运动距离和跑步时间明显增加(P<0.01).(2)安静组红肌(Ⅰ、Ⅱa型)MDA含量高于白肌(Ⅱb型)(P<0.05).力竭运动恢复期非训练组Ⅱa、Ⅱb型肌纤维MDA含量较安静组明显升高(P<0.05),训练组仅Ⅱb型肌纤维MDA含量升高(P<0.05).(3)与安静组比较,训练组在力竭运动恢复期Ⅰ型、Ⅱa型肌纤维T-AOC明显升高(P<0.05),但Ⅱb型肌纤维T-AOC无明显变化;而非训练组在力竭运动恢复期Ⅱb型肌纤维T-AOC较安静组降低(P<0.05).(4)与安静组比较,力竭运动恢复期训练组Ⅰ型、Ⅱa型肌纤维SOD活性升高(P<0.05),而Ⅱb型肌纤维SOD无明显改变,非训练组3种肌纤维的SOD活性在力竭运动恢复期与安静组相比均无明显变化.结论 运动训练选择性增强Ⅰ、Ⅱa型肌纤维SOD活性和T-AOC,减少自由基产生,这可能是运动训练改善骨骼肌运动能力的细胞机制.
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