You can continue to press your hands against the back torso, pushing the back up toward the ceiling as you press the backs of the upper arms down, onto your support. (yogajournal.com)
Because they both lie at the same angle and attach to the same area of the upper arm bone, they share the same job. (bodybuilding-wizard.com)
-- First, in a relaxed, sitting position, with your left hand feel your right biceps muscle on the front of your upper arm. (philmaffetone.com)