Resistance Band Tricep Extensions are an upper body exercise that focus mainly on the triceps.
How to do it
* Begin the movement by stepping on to a resistance band with your feet at shoulder-width, toes pointed slightly out.
* Push the handles of the band overhead while keeping a slight bend in the elbow. Brace your abdominals and do not arch your back.
* Slowly lower your hands behind your head using only the forearms. The upper arms will stay in place with the elbow pointed up.
* Push the handles back up, focusing the tension in the triceps.
Source Workout labs