What is the best and easiest way to firm up the triceps muscle of the upper arm?

Tricep exercises: Straight-bar cable pushdowns, lying overhead triceps extensions and cable rope extentsons are a few of the exercises that can be used.

Triceps work.: Triceps exercises include cable triceps extensions, overhead dumbbell extensions (one heavier dumbbell with both hands or lighter dumbbell in each hand), dumbbell kickbacks (light weight), close-grip bench presses, overhead cable extensions, and dips to name a few. Shoot for 3-4 sets per exercise, 8-12 reps, once weekly. Each day you work triceps, choose two of these exercises.