Diffusion tensor imaging (DTI) is a powerful technique that allows one to probe tissue at the microstructural level. Though microarchitecture determines the DTI indices, a diffusion model is required to make inferences about the microstructure. We applied a two compartmental diffusion model for muscle to explain differences in the DTI indices with age and with atrophy induced by limb suspension. The model qualitatively explains the changes in DTI seen in limb suspension that is linked to decrease in muscle fiber diameter and in intracellular volume fraction. Extensions to the model are required to explain the age related changes in DTI.