Antagonist : I am against the agonist , so I am famous as antagonist woohoo!😏 antagonist's muscles are acting against the agonist. for the example, we take the elbow flexion and extension. as we know biceps brachii and brachialis is acting together as an agonist for elbow flexion, here the extensor muscles of the elbow the triceps is antagonist's muscles. this both agonist and antagonist's muscles work under neurological reflex when agonist contracts antagonist goes under relaxation or vice-versa.