Article in English: Many office and personal desk chairs have adjustable backs, seats, and even lumbar support. Since the type of chair that you use will vary, try to keep the following criteria in mind:  Your upper legs should be flat against the bottom of the chair. Your lower legs should form a 90 degree angle at the knees. Your feet should be at a flat 90 degree angle to your lower legs. Your back should be at between 100 and 135 degrees in relation to your legs (if possible). Your arms should be tucked near your sides. Your shoulders and neck should be relaxed. Your eyes should be able to view the screen comfortably without having to stretch, crane, or strain your neck or your eyes. If your chair has lumbar support, a customized cushion, adjustable arm rests, or any other type of specialized support, adjust it as needed. It's okay to remove things like arm rests and cushions if they interfere with your posture. Your keyboard should be directly in front of your body; don't twist or bend your body in order to reach your computer. Ideally, your computer's screen will be at least one arm length away from you. You may be tempted to slouch your neck, thus bringing your chin close to your chest; this will lead to neck, shoulder, and back pain, so keep your head up even if you have to look down at the screen. One possible fix for this is adjusting your monitor's height so that it sits at your actual eye height. It's easy to take shallow breaths when sitting down, but doing so will eventually lead to other problems. Make sure to take deep breaths often—especially if you find yourself experiencing a headache or lightheadedness—and try to hold a few deep breaths in once every hour or so. Shallow breaths can cause you to adjust unconsciously your posture, while deep, diaphragm-level breaths will help you center your posture. If you have enough space on your desk to accommodate your documents, phone, and other accessories, make sure that they're arranged around the computer; your computer should be the center item on your desk.  Some...

Summary in Vietnamese:
Ngồi đúng tư thế. Điều chỉnh bất kỳ bộ phận hỗ trợ nào trên ghế. Ngồi sát vào bàn phím. Không cúi đầu. Hít thở sâu. Sắp xếp các tài liệu và đồ dùng xung quanh máy tính. Dành ít phút nghỉ ngơi nhiều lần trong suốt cả ngày làm việc để thư giãn cơ bắp. Tránh tình trạng mỏi mắt. Tập thể dục cho tay.