November/December 2019 Issue

Focus on Fitness: Float Therapy
By Jennifer Van Pelt, MA
Today’s Dietitian
Vol. 21, No. 11, P. 50

Alternative therapies are growing in popularity, especially those that aid in pain relief and stress reduction. Float or flotation therapy is increasing rapidly in use and accessibility; many spas, physical therapy practices, athletic training centers, and holistic health facilities are advertising “pods” or rooms for float therapy. Combining the muscle relaxation benefits of soaking in magnesium sulfate—more commonly known as Epsom salt—with the meditative aspects of sensory deprivation chambers, float therapy is being marketed for several health benefits, including the following:

• stress relief to combat anxiety and address posttraumatic stress disorder (PTSD);
• improving mood and relieving depression;
• joint and muscle pain relief due to fibromyalgia, arthritis, and injuries;
• easing the physical stress of pregnancy on the back and feet;
• relieving migraines;
• enhancing athletic performance by hastening posttraining recovery;
• improving physical and mental functioning; and
• improving insomnia and other sleep problems.

A float therapy session involves floating (with or without a swimsuit) in a pod or small room with a tank or pool. The water is approximately 12 inches deep and contains a very high concentration of magnesium sulfate salts, which prevents the body from sinking, inducing weightless or “zero-gravity” floating. The water is heated only to body temperature, so no therapeutic heat (as found in a hot tub) occurs in a float session. Earplugs are worn to keep water out of the ears, and a floating head/neck support generally is used, even though the salted water provides enough support to keep the face out of the water. The float pod has a lid that can be left open or closed. When closed, the pod is completely dark. Depending on the facility and float pod, floaters may be able to choose to listen to relaxing music and float with or without soft lighting. When open, the room housing the float pod generally isn’t completely dark, and the floater doesn’t experience full sensory deprivation.

Historical Context
Bathing in water enhanced with mineral salts has a long history as a therapeutic modality. “Taking the waters” was recommended by Victorian-era physicians for a variety of ailments, and Europeans flocked to the warm mineral springs in Bath, England, to soak. In addition, bathing in those natural mineral waters for health benefits can be traced back thousands of years ago to early Celtic, and then Roman, inhabitants of the United Kingdom. Use of water tanks for sensory deprivation originated in the mid-1950s with the work of neuroscientist John Lilly at the National Institute of Mental Health. Also called isolation tanks, sensory deprivation chambers were designed as a way to study consciousness by eliminating external stimuli.

Early tanks required total submersion with the use of masks for underwater breathing. By the early 1970s, magnesium sulfate salts were used in high concentrations to allow floating with the face above water and the first commercial float tank facility opened in California.

By the early 1980s, a research association to study float therapy was formed, and the phrase “restricted environmental stimulation therapy” (REST) was introduced to replace “sensory deprivation.” Though research continued throughout the 1980s and 1990s, the commercial industry was in a lull until the early 2000s, when float tanks made a comeback in the medical and spa communities.

Science Behind Float Therapy
The “zero-gravity” floating achieved in float therapy is due to the water’s very high concentration of magnesium sulfate. While research hasn’t definitively demonstrated that magnesium is effectively absorbed through the skin, advocates of float therapy believe absorbed magnesium during the hour-long float session acts as a muscle relaxant. Many individuals are deficient in magnesium as a result of inadequate dietary intake or certain medical conditions. Magnesium contributes to muscle fiber relaxation and calming of the nervous system; thus, it’s thought that the magnesium absorbed during a float session immediately relaxes muscles and calms nerves. However, it’s unknown whether muscle benefits following floating are due to magnesium absorption or just from the floating itself.

By eliminating external stimuli, the REST technique reduces the central nervous system’s workload by almost 90%, promoting relaxation by inducing the parasympathetic nervous system response. The floating and elimination of stimuli cause brain waves to slow to theta waves—REST researchers describe this as being like the “twilight” state between sleeping and waking. This deep relaxation state has been shown to benefit not only the nervous system but also the cardiovascular and musculoskeletal systems. The elimination of gravity on the body during floating releases muscular tension and promotes healing in joints and muscles. Vasodilation reduces blood pressure and heart rate while increasing circulation, providing cardiovascular benefits, according to REST researchers. Endorphins also are released during floating, which helps with anxiety, depression, and pain.

Despite decades of ongoing research, published evidence consists mostly of small studies; increasing interest is driven primarily by anecdotal reports from those who experience benefits from float therapy and media coverage of athletes and celebrities endorsing it. Studies reporting on muscle recovery and performance benefits for athletes were published in the 1990s and early 2000s.1-3 The largest published study, a meta-analysis of 27 smaller studies involving 449 participants that evaluated float therapy for a variety of applications reported that float therapy lowered cortisol levels and blood pressure, indicating positive effects on stress levels. Improved well-being and physical and mental performance also were reported.4 A 2013 study found that float therapy significantly reduced blood lactate levels and perceived muscle pain after exercise.5

Most recent research is focusing on float therapy for reducing anxiety, depression, and PTSD. A 2016 randomized controlled trial found that 12 sessions of float therapy significantly decreased anxiety symptoms, depression, and sleep problems, and symptom relief lasted at least six months. The researchers concluded that float therapy may be used as an adjunctive treatment for anxiety.6 In a 2018 study of the effects of one float session involving 50 people with anxiety and stress-related disorders, participants reported significant reductions in stress, pain, depression, negative mood, and muscle tension, and improved relaxation and overall well-being.7

Will Clients Be Interested?
Float therapy likely will be of most interest to clients who are avid exercisers or competitive athletes and those who have chronic musculoskeletal pain. Epsom salt soaks at home or in physical therapy are widely used for athletes’ muscle aches and pains—float therapy adds an opportunity for mindful meditation and visualization to enhance performance while muscles are recovering. Professional football, basketball, and baseball players; mixed martial arts competitors; and Olympic athletes are all using float therapy. Media reports have noted that many professional athletes have purchased float pods for home use. Clients who already have established mindfulness and meditation routines may enjoy meditating in a float session.

Published studies report no adverse events associated with float therapy, though anecdotal reports indicate that those with claustrophobia may not be comfortable with float pods with closed lids. And, while the salty water makes skin feel very smooth during the float session, it can cause dry hair and skin after the float session. High cost also may limit appeal. Pricing for sessions range from $50 to $100 for 45 minutes to an hour, but most facilities offer discounted first sessions for new patrons.

— Jennifer Van Pelt, MA, is a certified group fitness instructor and health care researcher in the Lancaster, Pennsylvania, area.


1. Bond J. Flotation therapy current concepts. Australian Institute of Sport website.

2. Kjellgren A, Sundequist U, Norlander T, Archer T. Effects of flotation-REST on muscle tension pain. Pain Res Manag. 2001;6(4):181-189.

3. Suedfeld P, Bruno T. Flotation REST and imagery in the improvement of athletic performance. J Sport Exerc Psychol. 1990;12:82-85.

4. van Dierendonck D, Nijenhuis JT. Flotation restricted environmental stimulation therapy (REST) as a stress-management tool: a meta-analysis. Psychol Health. 2005;20(3):405-412.

5. Morgan PM, Salacinski AJ, Stults-Kolehmainen MA. The acute effects of flotation restricted environmental stimulation technique on recovery from maximal eccentric exercise. J Strength Cond Res. 2013;27(12):3467-3474.

6. Jonsson K, Kjellgren A. Promising effects of treatment with flotation-REST (restricted environmental stimulation technique) as an intervention for generalized anxiety disorder (GAD): a randomized controlled pilot trial. BMC Complement Altern Med. 2016;16:108.

7. Feinstein JS, Khalsa SS, Yeh HW, et al. Examining the short-term anxiolytic and antidepressant effect of Floatation-REST. PLoS One. 2018;13(2):e0190292.