The present invention provides antibodies that bind to Activin A and methods of using the same. According to certain embodiments of the invention, the antibodies are fully human antibodies that bind to Activin A with high affinity. The antibodies of the invention are useful for the treatment of diseases and disorders characterized by decreased muscle mass or strength, such as sarcopenia, cachexia, muscle injury, muscle wasting/atrophy, cancer, fibrosis, and weight loss. The antibodies of the invention are also useful in combination with GDF8 binding proteins for the treatment of diseases and disorders characterized by decreased muscle mass or strength. The antibodies of the invention are also useful for the prevention, treatment, or amelioration of disorders and diseases caused by, promoted by, exacerbated by, and/or aggravated by Activin A, such as renal fibrosis.