That's likely to help cause muscle strain. The Natural Keyboard also slopes upward, meaning you either have to tilt up your wrists to reach the keys in the higher rows, defeating the idea of keeping your wrists straight, or hold you arms higher than normal, which is just plain bad. The best thing to have is a sliding, adjustable drawer mounted to the underside of your desk. Position your chair and desk so that when you pull the drawer out, the keyboard and mouse are at elbow level or lower. Some studies indicate that the best typing position is to have the back of the keyboard lower than the front, to keep your wrists straight.
Some adjustable drawers can tilt to that position.
You can also buy wrist immobilizers to help keep your wrists straight. But it's best to use them when you're not working. Using them as you type doesn't give you the flexibility you need. The mouse can also cause problems, by forcing your hand into a claw-like position. You might consider a big trackball, designed to help keep your hand open.