Effects of Swimming and Running Exercise-Induced Changes in Muscle Fibers, Bone Structure, and Oxidative Stress in Aging Rats

OBJECTIVE: The purpose of this study was to investigate the effects of weight-bearing and nonweight-bearing aerobic exercises on bone morphometry, muscle fiber types, and oxidative stress markers. METHODS: Eighteen 15-month-old male rats were divided into control, swimming, and running groups (n = 6 each). After a 2-week adaptation period, the exercise groups underwent 8 weeks of moderate-intensity swimming or running. Blood, gastrocnemius muscle, and femur bone samples were collected postexercise. Parameters analyzed included total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI) in blood, muscle fiber types by immunohistochemistry, and bone characteristics by histostereology. RESULTS: OSI values were similar across groups (P > .05), but oxidative stress was elevated in the exercise groups. The ratio of type I fibers was higher in the exercise groups compared to controls (P < .05) and similar between swimming and running groups (P > .05). Type IIa fiber ratio was highest in the control group and lowest in the running group (P < .05). Bone surface area, trabecular thickness, and cortical thickness were greater in the running group than in controls (P < .05). The swimming group had a higher distal femur bone area and trabecular width than controls (P < .05), but no significant differences were found between the exercise groups (P > .05). CONCLUSIONS: Weight-bearing and nonweight-bearing exercises had a significant effect on muscle fiber composition, bone structure, and oxidative stress in elderly rats. Running particularly enhanced bone surface area and thickness, while swimming also benefited bone health. Both exercises increased oxidative stress and antioxidant capacity.