Once the original Chi Machine® was released in 1990 in Japan, its popularity soared. Naturally enough other manufacturers launched there own versions. Japan has at least 20 different brands available. Soon there were many other brands being manufactured in China and Taiwan, as people throughout the Orient have a strong affinity for self-help healthcare devices and appreciated this newly found way of proactively taking care of their own health at home. Most of these new brands tried to achieve differentiation either by lowering the price, or by adding some extra functionality or new features. Inevitably lowering price often means reducing costs and therefore lowering the quality of parts, engineering design and/or build. The original Chi Machine® generally has good quality parts, and is well-built built with a solid engineering design. Many of the competing brands are lower quality, and you can easily notice the difference in the feeling of the ‘ride quality’. The better the engineering quality, the smoother the ride feels. And of course the smoother the ride, the more enjoyable and relaxing is the user’s experience. Other manufacturers started to compete with the original Chi Machine® by introducing new features. Some introduced multi-speed options – either with stepped speed controls where the user presses one of 2, 3 or more buttons to select a given speed; or by providing a dial control with which the speed can be adjusted gradually over a given range. There are of course differences between different models in terms of how effectively and precisely these speed controls work. Other manufacturers introduced ancillary features that allow users to utilize the same device for other purposes – such as vibrating foot massage effects, magnets and/or far-infra red radiation effects. Some brands even offer the option of having your head swung instead of the feet - with the aim of giving a neck or shoulder massage. The Sun Ancon® Chi Machine® has molded plastic leg cradles. Although its suppliers claim that the hard surface is important for massaging acupuncture points around the ankles (but also supply a separate fleece-like cover to help soften it), most users prefer a more comfortable support for their legs. Some manufacturers have therefore created leg cradles with softer surfaces or some form of padding. A related issue is the width between the cups for each leg. Recently the Sun Ancon® Chi Machine® has had a design change which recognizes that many Westerners are larger than the Japanese it was originally designed for – and have a need for more width between the legs. Some other models also have more latitude between the cups that cradle each leg. In Tai Chi and Chi Gong exercises most teachers suggest having the legs ‘shoulders-width apart’. We think this is a good measure to determine how comfortable the legs will be when held at different widths apart. On the other hand, some models have introduced leg cradles that have very broad and shallow-sided depressions for the legs to sit in – presumably with the aim of accommodating legs of larger girth. We think this development needs to be treated with some caution because we have noticed that it is important for the feet to be properly cupped or contained. If the cradles do not hold them properly in a roughly erect posture, the feet will tend to fall to one side. This is fine when we are at rest, but as we are looking here at simulating exercise, the feet and legs should be held as they would naturally be in a standing/ walking posture. If the feet are allowed to fall outwards, the joint between legs and pelvis changes significantly. For this reason we think it is important from a therapeutic viewpoint to have leg cradles which adequately cup the legs. Another line of improvements came from the introduction of heavy-duty DC motors, which are more robust than the AC motors used in the Sun Ancon® Chi Machine® and most other brands. The better DC motors used in some models are strong enough to give a noticeably smoother ride, and also have the benefit of a potentially long service life. DC motors also have a better capacity for precise control with adjustable speed functions. Another source of innovation has been with improvements to the hand controls. These are sometimes called “remotes” by some suppliers, though they are in fact attached to the machine via an electrical cord – so should not be confused with the unattached true remote control devices used with TVs and other appliances. The original Chi Machine® is fitted with a simple hand control with a dial for simultaneously switching on and setting the desired length of session time. There are now many different variations on this basic design, with the more advanced models using digital controls, including some with LED screens that show the various options, actual speed, session times etc. Finally, with some models there has been some divergence away from the original specification of the swinging movement of the leg cradle. Some models such as the Chi Vitalizer and the Surge of Chi Exerciser have a slightly broader width of travel. This allows for a greater degree of mobilization of the back. The wave-like motion up through the spine is more noticeable, and generally this changes the body’s “exercise feeling” significantly. The leg cradles on the Chi Vitalizer and the Surge of Chi Exerciser are also designed to have a slightly elliptical travel, and to have some flexibility in their forward-backward positioning – these features help users of many different heights, weights and shapes to feel comfortably supported as their feet are swung.