Ergonomic keyboard

An ergonomic keyboard is a computer keyboard designed with ergonomic considerations to minimize muscle strain, fatigue, and other problems. Ergonomic keyboards for two-handed typists are typically constructed in a V shape, allowing the hands to rest at a more natural angle.
Types.
Split keyboard.
Split keyboards group keys into two or more sections. Ergonomic split keyboards can be fixed, where you cannot change the positions of the sections, or adjustable. Split keyboards typically change the angle of each section, and the distance between them. On an adjustable split keyboard, this can be tailored exactly to the user.
Contoured keyboard.
A further development of the split concept are contoured keyboards like the 1977 Maltron or the newer Kinesis Advantage line, which place the keys into two depressions set approximately at shoulder width, with function keys set between the key groups for use with the thumbs. In this configuration, very little movement of arms and wrists is required.
Handheld keyboards.
Handheld ergonomic keyboards are designed to be held like a game controller, and can be used as such, instead of laid out flat on top of a table surface. They allow the user the ability to move around a room or to lean back on a chair while also being able to type in front or away from the computer. Some variations of handheld ergonomic keyboards also include a trackball mouse that allow mouse movement and typing included in one handheld device.
Angle split keyboard.
The angled split keyboard (sometimes referred to as a Klockenburg keyboard) is similar to a split keyboard, but the middle is tented up so that the index fingers are higher than the little fingers while typing. Key Ovation makes the Goldtouch ergonomic keyboard which is an adjustable angled split keyboard.
Other ergonomic keyboards.
Other ergonomic keyboards have fixed, vertically aligned keys, so the user types with their hands perpendicular to the ground, thumbs-up. Still others allow a range of rotation and elevations.
A few ergonomic keyboards do not have the typical one key per letter, such as a keyer or a keyless ergonomic keyboard. DataHand eliminates the need for any wrist motion or finger extension.
Considerations.
It is widely claimed that an ergonomic keyboard may reduce muscle strain and reduce risk of carpal tunnel syndrome or other kinds of repetitive strain injury. With respect to "split" keyboards, quality studies that demonstrate injury reductions are lacking, with the exception of physically split keyboards which have "sharply angled keyboard faces". There is evidence, however, that such keyboards are not well tolerated.
Narrow studies examining hand position at rest neglects many other possible factors. For example, one should be aware that the effect of “ergonomic” keyboards is to change the musculoskeletal region exposed to risk, instead of eliminating hazardous postures.