Hold a straight handle in front of you on a high cable attachment with the elbows flexed and palms forward. Keeping the trunk braced tightly, and the elbows close to the sides, extend the elbows maximally, then return to the top under control.
 
Purpose
The cable tricep pressdown is an effective way to isolate the triceps for strengthening elbow extension and general elbow stability.
 
Programming
Generally sets of 6-15 reps are appropriate.
 
Variations
Several types of handles and grips can be used to affect exactly what parts of the triceps are emphasized most, such as a V-handle or rope.