Abstract: It is reported herein that certain muscle diseases and conditions, including forms of muscular dystrophy, are characterized by impaired insulin-dependent signaling in the muscle tissue, in essence, a form of insulin resistance. The present disclosure relates to therapeutic agents, compositions and methods for treating a muscle disease or condition characterized by impaired insulin-dependent signaling by targeting components of the defective insulin signaling pathway. The disease or condition may be treated by administering a therapeutic agent that activates the insulin signaling pathway, in particular, therapeutic agents that act post-insulin receptor to modulate intracellular effector molecules. An exemplary modulator is metformin. Metformin may be administered alone or may be coadministered with another therapeutic agent for treating the muscle disease or condition, such as a corticosteroid.