Assists with flexion of the digits at the metacarpophalangeal joints. 1  Agonists: Dorsal Interossei, Palmar Interossei, Lumbricals, Flexor Digitorum Profundus, Flexor Digiti Minimi. 2  Antagonists: Extensor Digitorum, Extensor Indicis, Extensor Digiti Minimi.