Recent research suggests that electronic sit-stand workstations, that can be quickly adjusted, allow each worker to modify the height of their worksurface throughout the day, and this may reduce musculoskeletal discomfort and improve work performance.

Height adjustable, split worksurfaces -  with respect to wrist posture, the issues are the same for height adjustable, split worksurfaces and sit-stand worksurfaces:

• If the surface is too low the hand will be in greater extension
• If the surface is too high the elbow will be in sustained flexion
• If it's a flat surface then it's just the same argument as is used above for a negative-slope keyboard tray arrangement. 

You can't set a flat worksurface at an appropriate height for the 5 main tasks of office work - keyboarding, mousing, writing, viewing documents and viewing the screen- these all require different heights for an optimal  arrangement. A negative-slope keyboard tray system serves as the height and angle adjustment mechanism for the keyboard, and the mouse platform serves as the height and angle adjustment for the mouse when attached to a worksurface that is set for writing height. Monitor height is best adjusted by a separate monitor pedestal rather than trying to move a whole worksurface. There are a number of new split worksurface designs that may work quite well to achieve optimal monitor positioning.

The above 10 steps give a brief summary of good ergonomic design practice for computer workstations, but there's lots more to consider. You can read about ergonomics in many books, you can browse other materials on this CUErgo web site, you can get information from the Human Factors and Ergonomics Society. You can use the Computer Workstation Checklist to help to identify problems, and you can ask expert Ergonomists for help and advice.

Source: Cornell University