| | Conditions & Treatments | Bones, Joints & Muscles Why do you need two muscles to straighten your arm? To straighten the arm, you only need one muscle: the triceps brachii. The biceps brachii is responsible for flexing the arm. Bones, Joints & Muscles - Related Articles What does Five nonrib-bearing lumbar-type vertebrae? What Are the Benefits of Epsom Salts? How to Use a Shoulder Sling What makes one bones thicker than anothers? How to Remove Excess Icy Hot Cream About Sartorius Pain Is multifidus a deep muscle posterior to spine?
