Triceps cable extensions:
Stand as stable as possible; your feet may stay on one line, or one leg may be a little forward. The distance between them should be 15-20 cm or less. Press your elbows to the body, with the angle less than 90 degrees. Arch your back and look forward.
Stand with a slight lean, and using your triceps bring the bar down until your arms are fully extended. Make sure you are using only your forearms to push the bar down. After this, maintain your hold on the bar for a brief moment. Inhale as you bring the bar up again.
Mistakes and Recommendations:
Do not bend your wrists. They should be on the same straight line with the elbows.
Do not place your elbows widely. In this position, the broadest muscles of the back are working; it will be difficult to concentrate on your triceps.
Do not stand straight and do not slouch. Try to keep the right position.
Do not stand too close to the machine, but do not stand too far from it. In these cases it will be difficult to keep the right back position.
Keep your head in the right position, look forward.
Work with your triceps, not your back.
Remember about proper breathing pattern – exhale on the effort.

Triceps cable extensions.