People tend to hang out in Upward Facing Dog and focus solely on pushing up through their arms. When this is where your intention stays, your shoulders inch up toward your ears, your chest gets no opening benefits, and your legs stay on the ground. Underutilizing your shoulder, chest, and leg muscles in Upward Dog is a big mistake, since these are the parts of the body that should be doing the work in the pose!
Upward Facing Dog should offer a big release in the front of your chest and feel like a gentle backbend. According to yoga teacher Schuyler Grant, you should "always feel like you're pulling your chest forward and through, not pushing it up away from the floor." When you make this shift, you'll be keeping your shoulders and back safe while actively engaging (and strengthening) your arms and legs.
Source: Laughing River Yoga