A common technique used by massage therapists is to grip and squeeze large muscles firmly for a few seconds before releasing them. This can help relieve tension in tight muscles, prompting them to relax. Some massage chair manufacturers saw an opportunity to incorporate these techniques in their own products. But how do you make a device that squeezes a user without turning it into a dangerous machine better suited for a horror movie?
One solution is to use airbags. Several high-end massage chairs have multiple airbags. Two main areas of concentration are the user's arms and legs. That's because it's easier to isolate the extremities. It's also not likely to injure the user or hamper his or her ability to breathe.
Some massage chairs use multiple airbags to squeeze each arm and leg. A small air compressor inside the chair inflates the airbags. The air compressor connects to the airbags through a series of pipes or tubes. Some massage chairs include a switch that opens and closes air passageways so that the chair can inflate one set of airbags without affecting others. Other massage chairs use multiple compressors, each dedicated to a specific set of airbags.
A multiprocessor built into the chair connects to the compressor and tells it when to activate airbags during a massage. Some massage chairs allow users to adjust the intensity of the air massage. Intensity is proportional to inflation -- a fully-inflated airbag will provide a firmer squeeze.
Some massage chairs use airbags in the seat and backrest as well. By rapidly inflating and deflating the airbags, the chair can simulate the tapping method of massage. Inflating the bags at a slower rate simulates rolling or kneading. But most massage chairs rely on mechanical means to provide most of these features and use airbags as a supplemental massage device.
How do you control a massage chair, and what's up with chairs that can sense your body size? Find out in the next section.