Triceps Pushdown
Standing press down for triceps, or pushdown, (Triceps Pushdown), is one of the favorite triceps exercises. Its popularity is undoubtedly due to the fact that it affects all three heads of the muscle. Cable workout provides opportunity to influence triceps in a different way, as with exercise for mass. It must be noted that pushdown influences the lateral and middle heads while using greater resistance stimulates the long head as well.  When increasing the weight the middle and lateral heads need the support of the inner area of the triceps. As with other exercises for triceps, there exists the risk of cheating so one should be especially careful to follow the correct method of performing in order to benefit most from this exercise.
Vertical standing position is required
During the concentric phase there is a risk of bending forward to assist the movement. It is necessary to keep the vertical position of the body all the time for maximum accent on the triceps.  More advanced athletes can incline slightly during the cheating series to use bigger weight and achieve maximum hypertrophy of the white muscle fibers. However, if a beginner applies incline of the body during the movement, the load on the triceps will be lighter as the weight will be taken on by the chest and shoulder muscles.
Hold your elbows down, backwards and close to the body
There is a risk of opening apart the elbows during the concentric phase. If we let this happen, the chest muscles will be worked hard. Another risk is raising the elbows during the eccentric phase. One must keep them down for optimum extension of the forearm. 
Do not forget that arm extension is what activates the triceps. There is a tendency to move the elbows to the front of the body during the eccentric phase.  They must always be parallel to the body in order to achieve full amplitude of movement. Otherwise the exercise will lose its efficacy.

Method:
1. Take correct initial position facing the pulley above the head of the machine for triceps pushdown. Place your feet at shoulder width and bend them slightly at the knee and pelvic joints. The back must be straight and tight and the head raised. Do not bend forward; the chest must stay in vertical position, not inclined.
2.Take the straight bar with close under grip and pull it down to the upper part of the chest in order to take correct initial position.  Hold your elbows backwards and down, near the ribs and close to the body.
3. Begin the concentric phase by pulling the resistance downwards extending the forearms. You have to make an effort to keep your elbows in one and the same position down, backwards and close to the body.
4. Apply press while accenting as much as possible on the palms in order to forward quickly the nerve impulses to the outer area of the forearms and triceps. The danger in this movement is to put the accent on the thumbs and index fingers thus directing the nerve impulses to the inner area of the forearms and the front part of the deltoids.
5. Finish the concentric phase by pressing the weight downwards to full extension. Do not finish with a sharp movement. It is good to hold a bit counting to 2 or 3, tightening the triceps at the final point in order to send impulses to its uppermost part. Here exists the tendency to hold very shortly or not at all at the upper point, which does not allow activating the upper triceps area to the full.
6. When you become satisfied that the triceps has got maximum stimulation in all its length, leave the bar to rise slowly by strong nerve impulses. Beware of the risk of the forearms and shoulders taking on the load during the eccentric contraction. 
7. Let the bar stop in the final point of the eccentric phase making sure your elbows are down and backwards all the time during the movement.
8. Counteract the desire to swing your thighs to relieve the load. If your shoulders are included in the movement, the relief will be even greater but then the triceps will not get loaded enough. Swinging leads to pushing with the thighs, which gives momentum to the next concentric contraction and significantly reduces the effect of the exercise.
Important:
1. Keep the vertical position all the time, do not incline in the direction of the movement.
2. Hold your elbows in one and the same position down, backwards and close to the body during the whole movement.
3. Do not swing the body at the end of the eccentric phase.
4. Do not push your thighs in the beginning of the concentric phase.
5. Concentrate on not finishing the concentric phase with a sharp movement.
6. Do not spring at the end of the eccentric phase.