ABSTRACT
Objective:To investigate the effects of resistance exercise on mitochondrial function, muscle attenuation and muscle fiber morphology in quadriceps femoris of aged rats.Methods:The 18-month-old male rats were randomly divided into five groups( n=8, each): control(not exercise), 0% weight-bearing, 30% weight-bearing, 50% weight-bearing, and 70% weight-bearing exercise.After maximum resistance running, intermittent race table resistance exercise with 0%, 30%, 50%, 70% maximum load were performed.The treadmill placement slope was 35°, the running speed was 15 m/min, and exercise was performed every other day.At the end of the 8 th week, the mitochondrial membrane potential of quadriceps femoris muscle was measured, cytosol contents of cytochrome C(Cyt c), apoptosis-inducing factor(AIF), and apoptotic protein(Smac/DIABLO)were measured, and the morphology and structure of muscle fibers were observed. Results:Compared with the control group, the mitochondrial ΔΨmt was increased in the 0%, 30%, 50% and 70% maximum load groups, with a significant difference in the increment in the 0%, 30% and 50% maximum load groups( t=7.412, 5.611, 6.213, all P<0.01).Compared with the 0% maximum load group, the percentage of cells with mitochondrial ΔΨmt was statistically significantly decreased in the 30% maximum load group(10.6%)( t=9.356, P<0.05), while the percentage of cells with mitochondrial ΔΨmt was statistically significantly increased in the 70% maximum load group(10.03%)( t=8.341, P<0.05).Compared with the control group, the contents of Cyt c, AIF and Smac/DIABLO in the cytoplasm of quadriceps femoris of aged rats with 8-week resistance exercise were decreased, among which the contents of Cyt c and Smac/DIABLO were statistically significantly decreased in the three groups of 0%, 30%, and 50% maximum load( t=8.324, 7.516, and 6.871, all P<0.05), as well as the decrement in AIF of the three groups of 0%, 30%, and 50% maximum load was statistically significant( t =9.434, 8.78, and 7.342, all P<0.05).Compared with the control group, the vacuolar area of muscle fibers was extremely significantly decreased in the 0%, 30%, and 50% maximum load groups( t =5.567, 6.784, and 7.432, P<0.01); the protein content in the quadriceps femoris muscle was very significantly increased in the 30%, 50%, and 70% maximum load groups( t =7.478, 6.765, and 4.564, all P <0.01).Compared with the 0% maximum load group, the protein content in the quadriceps femoris muscle was very significantly increased in the 30%, 50%, and 70% maximum load groups( t=9.236, 8.342, and 6.456, all P<0.01). Conclusions:Low and medium weight-bearing resistance exercise can improve the mitochondrial function of quadriceps femoris, reduce the femoral quadriceps mitochondria-released proapoptotic proteins Cyt c, AIF, and Smac/DIABLO, and reduce the incidence of quadriceps femoris apoptosis.Low and medium weight-bearing resistance exercise can increase the protein content of muscle fibers, reduce the vacuolar area of muscle fibers, maintain muscle mass, and delay the occurrence of sarcopenia.