Many athletes around the world use Epsom Salt (magnesium sulphate) soaks to help with recovery post exercise, and magnesium’s critical role in the body has long been understood. A number of studies have shown that the bodies need for magnesium goes up as individual’s physical activity increased, and some studies have indicated that magnesium might enhance exercise performance by enhancing glucose activity (in the brain, muscle and blood), and by reducing/delaying lactate accumulation in the muscle .
Whilst there isn’t any firm scientific evidence that people absorb magnesium during Epsom Salt baths (the duration is too short, and the concentration of Epsom Salts too low), it has been shown that for the duration and concentration typically found in the Dead Sea (the same concentration and duration as during a float) the body will absorb some magnesium .
Even so, this is a secondary benefit, and ingesting magnesium supplements is still the most efficient way to boost magnesium levels in the body. The main benefits from floatation for muscle recovery come from having a weightless environment to allow your body to relax without any strain upon it, and allowing your mind to completely relax so that you can let go of any physical tension much easier (people often subconsciously tense their body in the area of an old injury to avoid further injury, but this strains the muscles and joints in that area) .
One underappreciated benefit of floatation for athletes, is having the perfect place to think things over and work through problems – many athletes will take advantage of this to mentally go over each aspect of their game in detail. Being able to mentally revise like this can help develop new techniques for doing things or enhance clarity during competitions.
 Can Magnesium Enhance Exercise Performance? (Yijia Zhang, Pengcheng Xun, Ru Wang, Lijuan Mao, and Ka He)
 Permeation of topically applied Magnesium ions through human skin is facilitated by hair follicles (Navin Chandrakanth Chandrasekaran, Washington Y. Sanchez, Yousuf H. Mohammed, Jeffrey E. Grice, Michael S. Roberts, Ross T. Barnard)
 Flotation restricted environmental stimulation therapy and napping on mood state and muscle soreness in elite athletes: A novel recovery strategy? (Matthew W.Driller, Christos K.Argus)