The triceps or triceps brachii consist of three heads, the long head, the medial head and the lateral head. The long head is the largest of the three and runs along the bottom part of the humerus or upper arm bone. The medial head is near the mid line and is mostly covered by the long head and lateral head. The lateral head is on the outward side of the humerus. Most triceps exercises simultaneously work all three heads but some emphasize the medial head.
You engage all three heads of the triceps when you do pushing movements in the gym and some body weight exercises, for example, dumbbell and barbell presses and pushups. The triceps are relatively small muscles that get a lot of use in the gym. Although small compared to some larger muscle groups, the triceps can comprise more volume than the biceps, which have only two heads. Do not over train them by doing an excessive number of direct triceps exercises or by focusing too much on individual heads such as the medial head.
Close Grip Bench Press
Do close grip bench presses. Lie flat on a bench and take a close grip on a bar, your hands approximately six to 12 inches apart. Keep your elbows tucked close to your sides and lower the bar to just below your nipple line. Focus on using your triceps to push the bar up. Lock your arms at the top of the movement. Do three sets of 10 to 12 repetitions.
Seated Dumbbell Extension
Seat on an incline bench with the incline set at approximately 85 degrees. Hold a dumbbell above your head with your palms upturned and the inner plates of one end of the dumbbell resting on your palms. Tilt your arms back slightly and, keeping your upper arm immobile, lower the dumbbell behind your head in a controlled fashion. Extend your arms back to your starting position and repeat for 10 to 12 reps. Do three sets.
Grip two parallel bars and balance your weight on your arms. Keep both arms straight, bend both knees slightly and cross your ankles to prevent your feet from dangling. Keep your body upright and lower your body until your upper arms are parallel to the floor. Do not lower your body farther, as too low of a position can stress the shoulders. Push your body up to your starting position. Focus on using your triceps. Do as many reps as you can. Do three sets.