Inversion tables have been marketed to decrease back pain, improve height, decrease stress, improve stretching, and mitigate symptoms from herniated discs and spinal stenosis…but what are they, and how well do they work?
Background
In the era of modern medicine, gravity inversion was introduced in the 1960s [1]. Dr. Robert Martin introduced what he called a “Gravity Guidance System” in an effort to address the effects of gravity on the human body. Dr. Martin became famous for this concept as he appeared on talk shows and in magazines, perpetuating the idea of the benefits of “postural exchange.”
“Postural exchange” is a fancy way of saying inversion. As the body inverts or hangs upside down, gravity has an opposite, negative effect on the spine compared to when we stand or sit right-side up. The idea behind inversion tables is allowing the spine to decompress in a noninvasive manner.
Dr. Martin was successful, and by the 1980s, an inversion fever was sweeping across the United States. This created a dangerous scenario when manufacturers competed in price wars. Cheaper products often corresponded with a sacrifice in quality. The result was disastrous. Several consumers were harmed, and inversion therapy in general became a target for skepticism and caution.
Anatomy & Table Design
Inversion therapy is a form of spinal traction [2]. The idea behind inversion tables is very straightforward. The user hang upside down (often at a safe and adjustable decline). By hanging upside down, gravity and body weight stretch the vertebral column in the opposite direction from normal day-to-day compressive forces. Although every inversion table is slightly different, the concept remains the same. Different inversion tables allow one to invert at varying degrees. Most people experience a greater benefit from inversion by only performing a partial inversion. This partial inversion is generally better than a complete inversion wherein the subject hangs upside down. Studies have shown that even slight inversions – within the range of 20° to 30° – may have myriad benefits.
Typically, these tables are designed for the human body to lay on them. About halfway down the table there is a balancing pivot. This tends to act as a teeter totter or balancing mechanism as if the user is laying on a see-saw and shifting the “head” toward the “down end” of the see-saw. When the user mounts an inversion table, he or she begins by anchoring the feet or ankles. The foot or ankle bars or straps are an integral safety feature of any inverting table. The anchors grab the legs at the ankles and lock them in place. This enables the user to relax completely as he or she is slowly tilted back and eased into a comfortable inverting position. If the subject does not feel safe in inverting position, muscular tension may decrease the effect of the treatment and/or risk injury.
There are typically handlebars or side bars that allow the user to control the inversion degree or intensity. Some tables feature preset degrees of inversion, enabling a measured and consistent degree to be used with the therapy. The handlebars enable the user to go from an upright position to an inverted one and then reverse the process, returning from inversion to being upright again to dismount the table.
Benefits
Part of the craze that happened in the 1980s with inversion tables was due to a study published in 1978 called “Inverted Spinal Traction.” This study made the observation that inverting lengthens the spine and reduces muscle hypertonicity [3]. The study had the direct implication that inverting reduced muscle spasms by reversing the gravitational compressive pressure on the spine.
It was even touted that inversion therapy can improve conditions such as disk herniations, spinal stenosis, and the general degeneration of the spine. It is noninvasive and does not use surgery. Inversion tables are a home therapy – it does not necessitate a visit to any health professional – though inversion and traction are used in several forms of manual therapy.
Inversion tables have been alleged to rehydrate the intervertebral discs, reduce nerve pressure, realign the spine, and relax tense muscles.
When one lies in bed at night, the removal of the compressive forces of gravity from sitting or standing all day causes the discs to naturally rehydrate by reabsorbing moisture and nutrition back into the disc. Some individuals have nerve root entrapment – commonly called a pinched nerve. Inverting may relieve this pressure as the vertebral column is stretched and elongated. A misaligned or degenerated bony structure in the vertebrae can lead to mechanical challenges with supporting the weight of the torso and head. When that happens, the task for support falls on soft tissues, and the resulting pain can be excruciating
When used as a therapy, inversion tables can be used to ease stress, increase flexibility, and be used as a fitness table to improve fitness and build core strength. Inverted squats may be an additional form of exercise.
Safety/Risks
The amount of time one spends on an inversion table inversely correlates to the angle of inversion; more steep angles should be met with decreased time. The user should not invert longer than what is comfortable [3]. Those who invert at it near 90° are often unable to remain in the position for more than a couple minutes at a time.
Another study in 1983 speculated that inverting can be particularly dangerous for people with glaucoma, hypertension, uncompensated congestive heart failure, carotid artery stenosis, hiatal hernia or spinal instability, individuals receiving anticoagulants or aspirin therapy, those above age 55 or those with a family history of cerebrovascular accidents [4]. As with all our educational articles, we recommend checking with a medical professional before starting any new practice.
References
[1] History of Inversion | Teeter Inversion
http://teeter-inversion.com/History-of-Inversion/
[2] Inversion Table | Big Back Pain
http://www.bigbackpain.com/inversion_tables.html
[3] The Upsides and Downsides of Inversion Therapy | Remedy Health Media, LLC
http://www.healthcentral.com/chronic-pain/c/23153/133392/inversion/
[4] Gravity inversion therapy. | National Center for Biotechnology Information
