Whether it is stiff elbows or stiffness of any part of our body while working on a computer, it is all our making. As a matter of fact, you should not spend excess time on a computer. Even if you are compelled to work continuously on a computer, you should take a break every now and then or once in a while or say you should take a break after every one hour of work on computer. Another thing is that whatever we do on computer, everything should be in moderation. By taking break of five or ten minutes at intervals of every one hour or so, you can just stretch your body, go and take some tea. This way you can breath some fresh air, refresh yourself and then return to work. This is what I do.