For this exercise, you need a band of rubber exercise tubing. Choose a low-resistance tubing until you become familiar with the exercise.
Grasp one handle in each hand, then step on the middle of the tubing with both feet. Stand straight up with your feet hip-width apart, knees slightly bent. Wrap the tubing around your hands so there is even tension on both ends.
Turn your palms to face forward, then slowly and evenly bring your hands up toward your shoulders, bending your arms at the elbows. Keep your elbows close to your sides and wrists straight and locked. Raise the handles only until your forearms are perpendicular to the floor, then slowly and evenly lower the handles to the starting position. Count one-two as you raise your hands, and one-two-three-four as you lower them. One-two. One-two-three-four.
When you are comfortable with the exercise, gradually increase the resistance of the tubing until you can do 18 to 20 repetitions using proper form. To increase resistance, shorten the tubing by wrapping it around each hand, or choose a higher resistance tubing. Once you can achieve 25 or more repetitions, increase the resistance to bring you back to the 18-to-20-repetition target zone.