I do not know the exact history of zero gravity massage chairs (also known as “anti-gravity”), but I will take a stab at it based on my own experience with massage chairs over the last 8-9 years, mingled with a little therapeutic angle based on my 19 years in the chiropractic profession.

Zero-gravity has become a fairly loose term in the massage chair industry as of late. Everyone sees to think that their chairs are zero gravity . When I look at the chairs that claim this feature, I am a little surprised at what is considered zero gravity and wonder if it is nothing but false advertising to get the zero gravity “crowd” to buy into a particular model since it has become such a catch phrase among shoppers.

History of Zero Gravity Massage Chairs
The whole concept of zero gravity was introduced by NASA for their space program. Human Touch, which is the largest US manufacturer of massage chairs, adapted the zero-gravity concept to household chair design, first displayed in their Perfect Chair line of chairs. According to Human Touch's website …

Inspired by the Neutral Body Posture studied by NASA during the Skylab program, the [Perfect Chair] zero gravity recliner places the body in a naturally weightless position to provide relaxation and minimum muscle tension. In this therapist-recommended position, the spine, hips, and knee joints are on or close to the balanced midpoint of the muscles.

The idea behind the zero gravity position is to take pressure off the joints of the body where strain tend to occur as a result of the gravitational pull, ie low back, hips, upper back, neck, knees, etc. I do not know if you are aware of this, but gravity is one of the most punishing forces of nature on the human body. If your body is not exactly aligned and balanced, gravity will make your body pay.

For example, if you have a forward head carriage and slouched shoulder posture, gravity is having a hay-day on your spell. You will feel more fatigued because your body is fighting the effects of the gravitational “pull”, not to mention the fact that your joints will wear out prematurely, leading to degenerative arthritis and other fun musculo-skeletal conditions.

If you have ever sat in a zero gravity chair, you fully understand the concept of “weightlessness” as it relates to the seated position. Many people have told me that they can sleep more comfortably in a zero gravity chair than they can in their regular bed. It is very comfortable, particularly for low back pain sufferers, as the chair positioning takes pressure off of the low back area.

So, What IS Zero Gravity?
Simply put, zero gravity, as it relates to the seated position, is having the seat of the chair tilt up at a 30 degree angle. That's it! That 30 degree tilt has been established to be, by engineers much smarter than I, the optimal position for simulated weightlessness of the human frame. Human Touch took that concept and applied it to the Perfect Chair model.

Then Human Touch took that model and applied it to a more bulky massage chair model, the HT-7450. Now, for the first time, a massage chair had the zero gravity feature. This, combined with the massage function, would provide a level of therapy heretofore unheard of in the massage chair industry.

Around this same time, Sanyo came out with the very popular Sanyo 7700 massage chair. The same 30 degree tilt of the seat, combined with massage therapy made this another of the zero gravity massage chairs. Both the Sanyo 7700 and the HT-7450 are very popular chairs for both manufacturers. I think the tilted seat makes them that popular.

Zero Gravity Massage Chairs – False Advertising?
So, why are all these other models claiming to be zero gravity chairs when their seats do not tilt up at 30 degrees? I have no idea. Again, I think it is just a marketing ploy to exploit the zero gravity “craze” that is current in the industry. Do not be fooled by claims of zero-gravity. Of course, any massage chair, whether it has true zero-gravity or not, is going to be fabulous for you in your home or office and you're going to love every minute of it. But, if you are determined to get one of the true zero gravity chairs, buyer beware!