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How to improve your posture at work
Adjust your chair height so your forearms line up with your keyboard.
Having to reach up or down with your arms when you're typing is bad for your posture. To have good posture at your desk, raise or lower your chair until your forearms are at the same height as your keyboard when you're typing.
Try to form a 90-degree angle with your elbows. Most office chairs have a lever or knob underneath them that you can use to adjust their height.