I don't have any personal experience with the Twiddler. But I have read a lot about computer-based repetitive strain injury and how to avoid it. Dr. Pascarell

I don't have any personal experience with the Twiddler. But I have read a lot about computer-based repetitive strain injury and how to avoid it. Dr. Pascarelli's book is a really good resource here. Normally the advice to "minimize finger movement" is really intended to protect your wrists, not your fingers. If you need to hit a key, but you avoid moving your hand and instead move your fingers, you will be stretching your wrist. If you consistently bend your wrist to the left or right (radial deviation or ulnar deviation) to reach notes, you may get carpal tunnel syndrome. This is basically an inflammation of the soft tissue surrounding the nerve that passes through the "carpal tunnel," a circle of bone in your wrist. The same thing happens when using a flat computer keyboard, and for the same reasons. This is why the correct keyboard posture is the V-shaped one, and the correct way to reach keys is to move your hand, not stretch your wrist. There are keyboard designs that can (almost) completely avoid ulnar and radial deviation. For example, the SafeType, a vertical keyboard, is a lot easier on the wrists. It's shaped roughly like an accordion, with the keys on both sides. This eliminates the temptation to bend your wrists to reach a key on the other side of the keyboard. The vertical "handshake" position is also a lot less stressful on the wrist than the flat keyboard one. There are finger issues that can come up if you strike the keys with too much force. These are especially a problem on the ultra-shallow (low travel) keyboards that Apple and other manufacturers are pushing now. In general, though, I would expect a design that only required finger movement to be much easier on the body than a traditional design, PROVIDED that the keys used were good quality, high travel keys. (This is a very important "provided" since a lot of keyboards nowadays are absolute garbage!) I'm curious if any research has been done on the ergonomics of chording keyboards. If not, perhaps research on RSI issues with trumpets would be a good proxy? In general, trumpet players don't have to move their hands, but only their fingers while playing. On the other hand, trumpets have a lot of vibration, which tends to exacerbate RSI issues.