A medical controversy has erupted over whether suspending oneself upside down in gravity boots is likely to trigger potentially serious eye problems, but the nature of the debate is such that a boot user trying to decide who's right is likely to be left hanging.
This dispute is like many disagreements in modern medicine. There is apparently good evidence supporting both the assertion that using gravity boots may be potentially harmful to the eyes--especially for people with glaucoma, diabetes, high blood pressure and sickle-cell anemia--and the rejoinder that there is no practical reason to believe the danger actually exists.
The situation may, however, leave people who indulge in hanging upside down in the United States--a popular way to treat oneself for backache--somewhat up in the air. That is because reputable researchers disagree on the danger question, as a whole, and because even the two ophthalmologists who believe the boots may cause eye problems--even in normal people--can't say how long is too long to hang.
While the dispute continues, though, makers of the boots note that using them is no longer a mere fad. Duarte-based Gravity Guidance Inc., which pioneered the boots more than a decade ago, claims to have sold more than a million sets. The company says several hundred thousand Americans hang upside down regularly in the belief they can strengthen their backs and decompress their spines.
Dr. Robert Martin II, son of the original developer of gravity boots, asserted that in the 15 years since inversion was first touted as beneficial exercise, there have been no reported cases of eye problems resulting from hanging. Moreover, a Chicago doctor who has written widely about health effects of gravity inversion--and is sympathetic to the cause--said two new studies he has conducted contradict the contention that users may face potential problems that could lead to at least temporary vision impairment.
But in an issue of a prominent medical journal to be published today, researchers at UC San Diego and the University of Texas Health Science Center in Dallas say that based on studies in subjects with glaucoma and normal vision, they recommend that people who have any of a series of eye disorders refrain from hanging upside down "altogether." The study also warns that even people with apparently normal vision should avoid "prolonged periods" of inversion because of the possible risk of eye damage.
At a Loss
The recommendations were made by Drs. Robert Weinreb of UC San Diego and Thomas Friberg of the University of Texas in an article that is being published in the Journal of the American Medical Assn. However, Weinreb and Friberg said they were at a loss to offer guidance to hangers about what "prolonged" means.
Pressed for some definition, Friberg said he would be comfortable with calling any period longer than 35 or 40 minutes "prolonged." It's uncertain what proportion of active hangers turn upside down for longer than that at any one time, however.
Weinreb said neither he nor Friberg, who have also described their research in the influential American Journal of Ophthalmology, had attempted to resolve the time issue and he emphasized that the potential eye problems they described are--for the moment--still best said to be theoretical. But, Weinreb said in a telephone interview, for patients with glaucoma or eye disorders related to diabetes, hypertension or sickle cell anemia, a short period is all that would be necessary to pose a theoretical risk of eye damage. "Thirty minutes would be worse than 10," he said.
Most at issue is hanging's effect on the retina, the innermost and one of the most crucial components of the eye. The retina has often been likened to film in a camera in terms of its critical role in perceiving visual images. It is the part of the eye that brings light rays that enter through the cornea into focus. Its vital blood supply comes from a sophisticated system of vessels.
Friberg emphasized the preliminary nature of the new research, conceding that "we clearly don't have any data that (say) we have people who suffered. We don't have one single individual who did." Both researchers urged caution in interpretation of their findings but urged caution, too, in use of gravity boots--at least until unanswered questions about vision effects can be resolved. The controversy has received added currency by publication this week in Medical World News, a widely read doctors' magazine, of a news account of the research in glaucoma patients.
Weinreb and Friberg conducted surveys on two groups of research subjects: 12 people who already had glaucoma and 16 other volunteers, all of whom were from 19 to 40 and had no eye problems or disorders linked to vision difficulties. Under controlled conditions, each research group was allowed to hang upside down while doctors measured blood pressures and other data designed to gauge whether the sudden and extreme flow of blood to the head that occurs in inversion brought about potentially dangerous increases in pressures on blood vessels in and around the eye.
Increased pressures were noted in both groups, though the measurements returned to normal soon after the subjects returned to a normal position. Though the results are clearly labeled as tentative, Friberg and Weinreb were concerned enough with what they found that, in both studies, they made recommendations similar to the conclusion in the one to be released today:
"Inverting for extended periods of time or performing strenuous exercises in this position could prove hazardous. We therefore discourage those with (a variety of) ocular conditions from participating in inversion activities."
Backers of the practice were quick to defend hanging. Gravity Guidance's Martin, for instance, contended that the new research is only tentative and preliminary--and, moreover, that it is contradicted by the experience of inversion partisans.
Martin, who maintains a rehabilitation medicine practice in Pasadena, said he has had a number of patients in their 80s and 90s who have done inversion exercise without ill effects and that, in fact, no patient in his experience has ever suffered an eye problem associated with hanging.
"What (the new study focuses on) is possibilities," he said. "It's like me walking across the street. I might get killed. It becomes so theoretical. I think they are going to have to reorganize their research.
Another Boot Backer
"Over a period of time, you'd think we would have had all sorts of retinal and glaucoma problems, yet we've never had one."
Martin quickly added, however, that any would-be hanger with glaucoma, sickle-cell anemia, high blood pressure or diabetes should be certain his or her condition is well controlled by drugs before taking up the exercise. Other boot backers have said they recommend any person with a pre-existing eye condition who wants to participate in inversion should obtain approval from his or her ophthalmologist beforehand.
Adding to the confusion are two other studies that recently appeared in the journal Physician and Sports Medicine--itself a prominent publication--that tended to discount any prospect of eye damage associated with gravity boot inversion. Both studies were conducted by Dr. Robert Goldman, a Chicago osteopathic physician and a gravity boot enthusiast.
In one of the studies, Goldman concluded people with uncontrolled high blood pressure should not indulge in inversion because existing hypertension would be exacerbated to possibly dangerous levels.
Goldman said he had noted increases in ocular pressure readings when he first started doing research in the field, as well, but that he concluded the elevations weren't dangerous because the readings quickly return to normal when the patient returns to the normal standing or sitting position and because the physiology of the skull provides some protection against eye damage by acting a little bit like a restraining cage.
"I don't think there is really much of a risk to the eye," Goldman said. He said that today's inversion backers recommend against simply hanging upside down without moving for long periods of time, anyway, preferring equipment that permits a hanger to move around and, preferably, to rotate back up to a straight position frequently during a hanging session.
Special equipment has been in common use for several years that permits a hanger to lie back on a sort of couch and rotate to the upside down position--and back to normal--at will.
"The message," Goldman said, "is that you should listen to your body and pay attention to how you feel."