Arnold Schwarzenegger always stood out biceps-wise and seemed to have the most outstanding brachialis muscle at the time. The function of the brachialis, according to wikipedia, is to “flex the arm at the elbow joint. Unlike the biceps, the brachialis does not insert on the radius, and does not participate in pronation and supination of the forearm.” You can train them doing hammer curl all day long but there actually is a bit of a secret to making brachialis stand out more. Lose body fat. Just like some discover that they have abs when they drop a few pounds, many see their brachialis for the first time when they lose enough body fat. That area of the arm seems to hold more body fat than, say, your biceps peak. Just like the triceps is an area where, especially some women, hold more fat. So, if you have been doing arm work for years and you still can’t see your brachialis in bold relief then you are going to have to face the fact that you are holding a little fat in that area and probably the rest of your body as well.
Training the brachialis: