Sit or stand up straight with a resistance band securely fixed under your foot.
Hold the other end of the band in your arm to be exercised.
With your arm straight by your side and palm facing backward, there should be some tension in the band.
Using your other arm, bend your elbow, bringing your hand up towards your shoulder.
When fully bent, remove the support of your other arm and control the movement as you straighten your elbow back out fully.
Repeat the movement, ensuring your bend your elbow with the effort all coming from your other arm.