Therapeutic Spectrum: Treatment of Rheumatologic Disorders with Aquatic Physical Therapy

Ask patients with arthritis why they like the pool and most say the same thing: it eases the pain. This article tests whether the physiology and the research back them up.

It first appeared in Advance for Physical Therapy.

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Published in Advance for Physical Therapy Magazine

Throughout this article, we will test the idea that aquatic therapy is an effective treatment for the impairments, functional limitations and disabilities commonly associated with rheumatic diseases. This article addresses one of the aquatic benefits most commonly cited by the anecdotal press for the treatment of rheumatologic disorders.

Building a Case 

Patients with rheumatologic disorders suffer from subjective complaints, including muscle spasm, pain and stiffness. Individuals with these symptoms seek relief from them. Exercise in a gravity-based environment may exacerbate the pain cycle, whereas patients may be able to exercise without discomfort in the water. Hypothesized benefits are decreased pain and decreased muscle spasm.

Hypothesis: Exercise and/or relaxation in water provides a palliative thermal effect and a reduction in postural muscle activity, and thus leads to decreased pain and decreased muscle spasm.

Building an Argument 

I. Hydrodynamic principles 

Although dependent on the population using the facility, therapeutic pools are generally heated to between 92 and 97 degrees Fahrenheit.¹  At temperatures above "thermoneutral"

(approximately 93-95 degrees Fahrenheit at rest and 91-92 degrees Fahrenheit during mild exercise),^2,3 body temperature increases due to the reduced ability of the body to dissipate heat through the skin.^4,5 Thermal energy (heat) is exchanged between water and the body and between air and the body.⁴ Energy exchange between a submerged body and the water occurs through both convection and conduction.⁴

Convection creates thermal shifts more rapidly than does conduction, but requires movement of water across the skin or movement of the body through water to occur. Convection transfers heat in the direction of the lower temperature. If the water temperature is warmer than thermoneutral, thermal energy is transferred to the skin or "outer shell" of the body and is then shuttled to the thorax or "core" via the venous system. Conduction, unlike convection, occurs due to physical contact between the water and the body, and does not require movement within the water to occur. Immersion alone in water warmer than the skin results in conduction of thermal energy from the water to the body's shell, and eventually, to its core.

Thermal energy is also exchanged between the body and the air through radiation and evaporation, methods which become more critical if the total body is immersed and the water temperature prevents heat dissipation from occurring during aquatic exercise.⁴

Immersion in water warmer than the skin will result in a rise in superficial tissue temperature which creates a palliative effect like that experienced during the therapeutic use of paraffin,

Fluidotherapy® and moist heat.⁵  The mechanism of pain relief may come from one of several phenomena. The application of external heat may:

1) Create reflex mechanisms by stimulating cutaneous afferents, creating a "soothing counterirritant effect;"^1,5

1. Inhibit gamma motor (efferent) firing, which lowers the stretch on the muscle spindle, which then reduces the afferent firing from the spindle.¹  The reduction in the "walled off effect" or muscle guarding would permit blood flow to restore normal oxygenation of tissues and removal of chemical irritants (wastes) which would enhance nutrition, diminish stiffness, and decrease ischemia-induced pain;^6,7
2. Penetrate the surface deep enough to elevate the temperature of muscle spindles and golgi tendon organs, thus decreasing their firing rate (via a reduction in discharge of secondary muscle spindle afferents).¹  The reduction in the "walled off effect" or muscle guarding would permit blood flow to restore normal oxygenation of tissues and removal of chemical irritants (wastes) which would enhance nutrition, diminish stiffness, and decrease ischemia-induced pain;^6,7
3. Stimulate thermal receptors which create impulses which then travel on A delta and C nerve fibers to the spinal cord. This thermal input inhibits pain impulses (traveling on the same A delta and C fibers) before pain input reaches synapses in the spinal cord;
4. Accelerate both metabolic functions (of cells) and circulation of blood and lymph.¹  This increases oxygenation of ischemic muscles and promotes elimination of the chemical irritation of waste which then decreases muscle ischemia and toxemia and decreases sensation of pain.^6,7

II. Clinical Research 

Clinical research has demonstrated that aquatic therapy can reduce pain in patients with rheumatological disorders, even though this improvement has not always been shown to exceed the benefits of land-based exercise.

Green and colleagues assessed the treatment effectiveness of home exercise alone versus the effectiveness of home exercises plus hydrotherapy for osteoarthritis of the hip.⁸ Subjects had a median age of 67 years. Group 1 received instruction in home exercises only. These five exercises were: leg swinging (flexion/extension and abduction/adduction), an internal rotation hip stretch, resisted standing hip abduction, and "raising the trunk upwards off the affected leg." Group 2 received the same home exercise instruction, but additionally attended hydrotherapy twice a week.

Among other parameters, the authors examined pain (visual analog scale), descriptive pain scale, and the amount of pain medicine consumed. Subjects in both Group 1 and 2 showed highly significant improvement in the combination of parameters tested. Final visit: This improvement continued over the next six weeks and the final assessment (week 18) showed marked improvement over control values for both the land-only and the aquatic-plus-land groups. The authors found no significant difference in the treatment results obtained by the self-treatment group and the self-treatment plus hydrotherapy group. However, this was not a comparative study.

Meyer and Hawley examined the relative characteristics of patients who participated in aquatic exercise versus those who did not.⁹ Patients who participated in an aquatic exercise class were in significantly less pain than those who did not. This phenomenon can be explained with one of two reasons: 1) the more involved patients (those with a higher baseline of pain) did not choose to participate in a water-exercise class and thus were overly represented by the non-exercise group; or 2) the patients who exercised in the water experienced a subsequent reduction in pain, which then resulted in a lower pain score than their non-exercising counterparts. With more study, it will be possible to determine which reason created the difference.

Templeton, Booth and O'Kelly did find a significant decrease in subjective rating of pain (10-point pain scale) over baseline in patients who participated in a 45-minute, twice per week, eight- week aquatic exercise class taught in water at 91 degrees Fahrenheit.¹⁰ The researchers statistically assessed the effects of that reduction in pain and found that this reduction was at least partially responsible for a subsequent significant improvement in hip, ankle, wrist and shoulder active ROM. The researchers were unsure which elements of "aquatic intervention" were responsible for the reduction in pain, and suggested future studies which teased out the relative contributions of immersion alone, exercise alone, and alterations in lifestyle (such as change in medications) which occurred during the trial period.

McNeal hypothesized that the decreased subjective complaints of pain in populations with rheumatic diseases result from the additional sensory input received from the temperature of the water in combination with turbulence and pressure.¹¹ Furthermore, the literature indicates that aerobic exercise positively affects mood (which affects pain) through the mediating effects of beta endorphins and other factors.^12–16 The well-known fragment of amino acids "61-69" (beta-endorphin) is only one of more than 18 molecules found naturally in the brain which have strong pain palliation effects.¹⁷ These analgesic brain peptides are affected by levels of activity and should respond similarly to exercise performed in an aquatic- or land-based setting. As it is possible that the hemodynamic shifts which occur with immersion may affect brain chemistry, this assumption should be made cautiously until further research is done.

For education only; not a substitute for individual clinical judgment.