This is a good exercise for the back of the arms (triceps) and the front of the shoulders (anterior deltoids).
Begin by sitting down on a chair or a low coffee table. Place your hands on the edge of the chair or table next to your hips. Straighten your arms and raise your hips up and away from the edge of the chair/table, at the same time walk your feet out about 2-3 feet, then slowly lower your body down by bending your elbows as shown in the image, return by straightening your arms; repeat 10-15 reps 3 sets.