A growing number of people are expected to know how to use computers to satisfy the demands of their job. Without proper training, workers are prone to injuries of the hand, wrist, and back. Working at the computer demands proper angles. The top of the monitor should be at eye level, so that the center of the screen is viewed slightly downward. The keyboard should be on a flat surface, with the user's arms relaxed, loose, and at a ninety degree angle. Forearms and hands should be parallel to the floor. The back should be angled slightly to the rear to increase blood circulation and reduce compression of the spine. The chair should fit the curve of the lower back, with the seat angling forward slightly to reduce pressure on the spine.