All 3 variations still train all 3 heads — these are just biases based on joint position, grip, and tension. No single exercise “isolates” one head choose based on what you want to emphasize and how it feels for you. Pronated (overhand) grip → Targets all 3 heads → Greater emphasis on the lateral head * Pronated grip = more internal rotation elbow extension Supinated (underhand) grip → Targets all 3 heads → Slightly more medial head involvement * Supination shifts elbow mechanics → increases med