It is well documented that water immersion to the chest reduces body weight by as much as 68%. This means that a person who weighs 170 pounds on land will weigh about 54 pounds in chest-deep water thanks to buoyant forces that counteract gravitational forces. This weight reduction is particularly relevant to any person who experiences joint pain. An astonishing 75-85% of the population will experience some form of low back pain during their lifetime. Many management plans for treating low back pain recommend some form of aquatic exercise therapy, as many people are simply unable to perform the necessary exercises on land because of the load-elicited pain from body weight.
The use of aquatic exercise therapy for treating back pain has many theoretical advantages over land-based exercise programs. For example, buoyancy reduces spinal loads, and hydrostatic pressure and temperature of water assists with balance, pain control, and mobility. Accordingly, people with back pain who find it difficult to perform land-based exercises may successfully perform aquatic-based exercises first and then progress to more functional land-based exercises.
Curiously, most muscles surrounding the low back are less active in water than on land. The lower activation levels in water are sufficient to improve motor control and endurance aspects of most low back muscles. In addition, these lower muscles activation levels are considered to be safer. For example, greater activation levels that are often observed on land (>40% of maximal), raises the likelihood of joint pain or injury to the spine. In this view, aquatic-based exercises produce a more appropriate activation level of the muscles surrounding the back, which is ideal for people with heightened back pain. In summary, the aquatic environment may be the most appropriate medium for people with back pain to begin strengthening the back muscles.