Many massage chairs come with a pre-programmed list of massage therapies. A user sits in the chair and selects whichever therapy he or she wants from a list, usually using a remote control. Since there is little or no need to operate a massage chair remotely, most massage chair remote controls are wired directly to the chair.
A microprocessor inside the chair stores the information for each massage pattern. When a user selects a particular therapy, the microprocessor sends commands to the chair's various massage apparatuses. Though a user can't modify a chair's massage patterns, many chairs allow users to adjust the intensity of the massage using the remote. The microprocessor then sends commands to the appropriate apparatus, which adjusts its intensity.
Some chairs have complex interactive devices. If you shop around for a high-end massage chair, you might see one that includes an infrared body scanner. These scanners are really just a series of infrared sensors that can detect at what points a user's body comes in contact with the chair. The sensors send the information to the microprocessor, which then makes some calculations and sends new information to the massage apparatus.
Since several people might use the same massage chair, it's important to be able to make these adjustments. For example, a six-foot (1.8-meter) tall user's back will make contact with more of the chair's backrest than a user who is only five feet (1.5 meters) tall. A neck massage for the six-foot tall user would likely feel very odd to someone much shorter -- if they were tall enough to feel it at all. By scanning the user's body, the chair can adjust so that the points of contact for each person are the appropriate height and width.
Some massage chairs monitor the user's responses to the massage, adjusting intensity and concentrating on specific areas on the fly. The Sanyo Zero Gravity Massage Chair includes sensors that monitor galvanic skin response. This is the same sort of technology lie detector machines use to monitor a person's response to questioning. The galvanic sensors measure the user's pulse rate and perspiration. When the chair detects an increase in these metrics, it interprets the data to mean that the area currently being massaged is particularly tense or stiff. The chair's microprocessor alters the normal pattern to spend more time on that area [source: Sanyo].
A few massage chairs include voice-response software. This software can interpret and respond to vocal commands from the user. The list of commands is usually a small subset of the chair's overall capabilities.
Will massage chairs ever move out of the luxury market and become common in households across the United States? That's the hope of many manufacturers. But for now, it looks like the price of massage chairs will continue to limit the size of the market.
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