Type 2 diabetes mellitus (T2DM) adversely affects skeletal muscle, contributing to weakness, functional decline, and reduced mobility. Although lower-limb muscles are essential for locomotion and independence, it remains unclear whether diabetes affects these muscles uniformly or whether certain muscle groups are more vulnerable. Resistance training (RT) is widely recommended for individuals with T2DM

This narrative review synthesizes evidence from human studies on structural and functional alterations in the quadriceps, gastrocnemius, and soleus muscles in adults with T2DM. We propose that fiber-type composition may be a key determinant of muscle-specific vulnerability. Because the soleus is composed predominantly of type I (slow-twitch, oxidative) fibers, which are particularly susceptible to mitochondrial dysfunction, impaired glycogen metabolism, and chronic metabolic stress, we hypothesize that it undergoes earlier and more pronounced deterioration than muscles with a more mixed fiber composition.

Current evidence consistently demonstrates reduced quadriceps size, strength, and muscle quality in T2DM, whereas studies of the calf muscles remain limited despite their critical role in gait and balance. Emerging imaging and mechanistic evidence suggest that the soleus may exhibit early diabetes-related microstructural alterations. RT improves muscle strength, physical function, and metabolic health; however, no human study has directly compared the responses of the quadriceps, gastrocnemius, and soleus to the same RT protocol.

Overall, available evidence supports regional heterogeneity rather than uniform lower-limb involvement in T2DM. A fiber-type-informed, muscle-specific perspective may improve understanding of diabetes-related muscle dysfunction and guide the development of more targeted resistance training strategies to preserve mobility and functional independence.