Influence of exercise and tenectomy on the morphology of a muscle nerve

The effects of decreased and increased levels of muscular activity on the morphology of the medial gastrocnemius nerve were investigated in male albino rats assigned to tenectomy, control and exercise groups. Nerve fiber diameter and the number of constituent myelinated fibers were measures obtained from images of transverse sections projected onto drawing paper. The mean values for the tenectomised animals for nerve fiber diameter (X = 7.41 ± 0.13 μ) and number of nerve fibers (X = 223 ± 5.4) are significantly lower than the means of the control animals (X fiber diameter = 7.96 ± 0.14 μ; X number of fibers = 247 ± 5.2). Associated with these changes is a marked atrophy of the gastrocnemius muscle. A single bout of exercise (running in an activity cage) did not produce changes in nerve fiber diameter (X = 7.58 ± 0.17 μ) nor in the number of nerve fibers (X = 238 + 5.0). Moreover, an eight‐week exercise program consisting of running on a treadmill had no significant effect on mean nerve fiber diameter (X = 8.04 ± 0.18 μ) nor in the number of nerve fibers (X = 231 ± 6.3). Correlations between gastrocnemius muscle weight and mean nerve fiber diameter or number of nerve fibers revealed no significant relationships. It was concluded that only the tenectomy data supported the theory of interdependency of muscle and nerve.