Prolonged Endurance Exercise Decreases Fiber Loss And Fiber Atrophy In Aged Male Rats

Sarcopenia is the age‐related loss of muscle mass and function. Effects of long‐term exercise training on sarcopenia have not been well defined. In this study we assessed skeletal muscle adaptations to prolonged exercise training in rats from late‐middle age to old age. Male rats, 24 mo of age, trained on a treadmill at three levels of intensity: high (HI: 13m/min, 5% incline for 30 min, 5 days per week), moderate (MI: 13m/min, 0% incline for 30 min, 5 days per week), minimally active (MA: 5m/min, for 5 min, 2 days per week) and a sedentary group (S). Rats ran for one year until the rats were age 36 months. The rectus femoris (RF) muscle from 24‐month Controls (C), and 36‐month HI, MI, MA, and S. The RF was weighed, bisected, frozen, sectioned and stained with hematoxylin and eosin. Digital images of RF cross‐sections were used to determine muscle area, fiber number and fiber diameter. Aging significantly reduced muscle mass, muscle area, fiber number and fiber diameter, (24‐month C compared to any of the 36‐month old S, MA, MI or HI). Among the 36‐mo. rats (HI, MI, MA, and S), no differences were observed in muscle mass or muscle area. However, there was a significant increase in fiber number and fiber diameter in all exercise groups (HI, MI, and MA) compared to S. These results indicate that any level of exercise, even minimal levels of activity is capable of decreasing the effects of sarcopenia in aging rats. Supported by NIH AG 030423.