A common ergonomic problem is stress to the back, shoulders, and neck. The back cannot tolerate excessive lifting, bending or twisting. Anyone who uses a computer as a regular part of the workday can describe the tension in the shoulders and neck produced by crunching over the computer. People are different, we all know that people come in different shapes and sizes. Some of us are tall, others short.
Most office chairs are adjustable.
Your back should rest comfortably against the back rest and your feet should rest flat on the floor with your knees at the same height as your hips. Use a lumbar cushion or rolled towel if your chair does not support your lower back. Improved layout is usually the best approach for eliminating this problem. The weight of the upper body, head and arms is load enough for the spine. This is also true for the neck.