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Evidence-Based Case for Aquatic Therapy
for the Patient with Arthritis
©1997-2007, Aquaticnet.com


Part 1
It
is already widely accepted that one of the most effective treatments for long-term management of the symptoms of rheumatologic disorders is physical exercise.

However, it has been suggested that weight-bearing exercise — even exercise considered "normal" — can aggravate pain and further promote degeneration in patients with abnormal joints.

This is particularly true if the joints have incongruous articular surfaces, poor alignment, ligamentous instability, or altered muscle or joint innervation, as is often the case in patients with immunologic conditions.

Unfortunately, this diminishes exercise options for the patient with joint degeneration, which often results in a discontinuation of exercise altogether. Ironically, the ensuing immobility and lack of dynamic joint loading further damage joint surfaces leading to a downward spiral of immobility and degeneration.

Throughout this column, we will test the idea that aquatic therapy is an effective treatment for the impairments, functional limitations and disabilities commonly associated with rheumatic diseases.

Below, you will find the aquatic benefits most commonly cited by the anecdotal press for the treatment of rheumatologic disorders. Each hypothesized benefit will be examined in turn.

Building a Case
Aerobic exercise is an important treatment for patients with rheumatic disorders since they tend to be physically deconditioned. This deconditioned state promotes a continued cycle of pain, fatigue, and decreased motivation, leading to inactivity which further exacerbates the cycle. The therapeutic pool offers a reduced weight-bearing environment where patients can still achieve cardiopulmonary rewards associated with aerobic conditioning.

Hypothesized Benefits
Increased aerobic capacity; increased endurance. Improved ventilation, respiration (gas exchange), and circulation.

Hypothesis
Aerobic exercise in an aquatic environment leads to increased aerobic capacity and increased endurance, and improved ventilation, respiration (gas exchange) and circulation.

I. Hydrodynamic Principles
Buoyancy
The therapeutic pool offers an environment for aerobic exercise that is no- or low-impact, permitting aerobic exercise without the negative consequences of excessive joint compression. So, how does buoyancy create a therapeutic environment?

Archimedes' principle states: "When a body is wholly or partially immersed in a fluid, it experiences an upthrust equal to the weight of fluid displaced." This upthrust, or buoyancy, counterbalances gravity and supports the body, resulting in an apparent reduction in weight bearing through the spine and lower extremities.

Therefore, exercise in water can produce less spinal and lower extremity joint compression than the identical exercise performed on land, offering patients with rheumatologic disorder an environment where it is possible to exercise aerobically.

Hydrostatic Pressure
As already established, the therapeutic pool offers an environment for aerobic exercise that is no- or low-impact. Interestingly, an argument can be made that this environment can also provide cardiopulmonary training effects that are similar to, or better than, those achieved on land. Why? In part, this is due to the effects of hydrostatic pressure.

Pascal's Law states, "Fluid pressure is exerted equally on all surfaces of an immersed body at rest at a given depth." Thus we know that pressure increases as depth increases. Since the density of the fluid in most therapeutic pools is fixed and unalterable, this pressure gradient can be used therapeutically.

In essence, hydrostatic pressure increases the pressure on the outside of an immersed standing body, resulting in:

  • A reduction in edema and an offsetting of blood pooling in the lower extremities (by providing graduated pressure at greater depths).
  • A slowing of the heart rate during exercise in water (especially in cooler water) by increasing the shift of blood to the thorax, increasing pre-load of the heart, and thus increasing stroke volume. This results in greater perfusion of coronary arteries and a more efficient cardiopulmonary system during exercise.

It is also important to remember that hydrostatic pressure can restrict chest wall expansion in individuals with compromised pulmonary systems and thus serve as a progressive resistive exercise program for respiration.

II. Scientific Research
Although the beginnings of a solid case can be made based on hydrodynamic principles alone, there has also been some research that has examined whether aquatic therapy can benefit the cardiopulmonary fitness of rheumatologic patients.

Jentoft et al examined the effects of pool-based and land-based exercise programs on patients with fibromyalgia.1 The outcomes were assessed by the Fibromyalgia Impact Questionnaire, the Arthritis Self-Efficacy Scale, and tests of physical capacity. After 20 weeks, statistically significant improvements were seen in both groups in cardiovascular capacity, walking time and daytime fatigue. The results were mainly unchanged at six months followup. The researchers concluded that physical capacity can be increased by exercise, even when the exercise is performed in a warm-water pool, and that pool programs may have some additional effects on symptoms.

Melton-Rodgers et al compared the aerobic effects of land-based biking versus water-based running for subjects with a diagnosis of class II or III adult-onset rheumatoid arthritis.2 There were no significant differences between the two training environments for the following factors: peak VO2, maximum heart rate, perceived exertion (RPE) at 60 percent peak VO2, or pain. Peak minute ventilation on the bike was 26 percent higher and peak tidal volume was 48 percent greater than that achieved during water running (significantly different). Conversely, peak RPE was 7 percent higher and peak respiration rate was 22 percent greater in the water than during land-based bicycling (significantly different). The authors concluded that it was possible to achieve training effects during water running for the population and parameters studied.

Minor et al examined a group of patients with rheumatoid arthritis or osteoarthritis who volunteered to be subjects for this study of aerobic versus nonaerobic exercise.3 Patients were randomly assigned to an exercise program of aerobic walking, aerobic aquatics, or nonaerobic range of motion (controls). The researchers showed a significant training effect over controls by having rheumatologic subjects participate in either land- and water-based aerobic exercise. Aerobic capacity, 50-foot walking time, and physical activity improved after participation in the 12-week exercise trial. Their findings document the feasibility and efficacy of conditioning exercise for people who have rheumatoid arthritis or osteoarthritis.

Danneskiold-Samsoe et al examined the effect of exercise therapy performed in a heated swimming pool for patients in a non-acute stage of rheumatoid arthritis.4 After two months exercise therapy, the researchers noted a significant improvement in aerobic capacity in patients with Class II or III rheumatoid arthritis after participation in a twice/weekly, eight-week aquatic exercise program.

Bacon et al examined the effects of aquatic therapeutic exercise on lower-extremity range of motion, gait, balance and functional mobility in children with juvenile arthritis.5 In this pilot study, patients age 4-13 with lower-extremity joint involvement, diagnosed as functional class I-III, completed a six-week program of aquatic exercise aimed at increasing lower-extremity range of motion and strength. The researchers found a significant reduction in post-exercise recovery heart rate after patients with juvenile rheumatoid arthritis participated in a twice/weekly, six-week aquatic exercise program. Researchers felt that further investigation was warranted to determine fully the effects of aquatic therapeutic exercise on mobility and fitness in children with juvenile arthritis.

Conclusion
There have been hundreds of scientific articles written on the cardiopulmonary benefits of non-swimming aquatic exercise for "normal populations."6 It is no longer a question of "if" aquatic exercise can improve cardiovascular fitness—it is now just a question of whether the same holds true for patients with compromised health (such as the patient with osteoarthritis or fibromyalgia ).

This column attempts to establish the beginning of a hydrodynamic and scientific basis for the use of aquatic therapy to improve the cardiovascular health of the rheumatic patient.

References
1. Jentoft, E., Kvalvik, A., Mengshoel, A. (2001). Effects of pool-based and land-based aerobic exercise on women with fibromyalgia/chronic widespread muscle pain. Arthritis Rheumatology, 45(1), 42-47.

2. Melton-Rogers, S., Hunter, G., Walter, J., & Harrison, P. (1996). Cardiorespiratory responses of patients with rheumatoid arthritis during bicycle riding and running in water. Physical Therapy, 76(10), 1058-1065.

3. Minor, M., Hewett, J., Webel, R., Anderson, S., & Kay, D. (1989). Efficacy of physical conditioning exercise in patients with rheumatoid arthritis and osteoarthritis. Arthritis Rheumatology, 32(11), 1396-1405.

4. Danneskiold-Samsoe, B., Lyngberg, K., Risum, T., & Telling, M. (1987). The effect of water exercise therapy given to patients with rheumatoid arthritis. Scandinavian Journal of Rehabilitative Medicine, 19(11), 31-35.

5. Bacon, M., Nicholson, C., Binder, H., & White, P. (1991). Juvenile rheumatoid arthritis: Aquatic exercise and lower-extremity function. Arthritis Care Research, 4(2), 102-105.

6. Salzman, A. (2002). aquatic therapy research Bibliography. Aquatic Resources Network: Amery, WI.



Part II

Throughout this five-part series, we will test the idea that aquatic therapy is an effective treatment for the impairments, functional limitations and disabilities that are commonly associated with rheumatic diseases.

Building a Case for Treating Rheumatologic Patients with Aquatic Therapy
Patients with rheumatological disorders experience stiffness, complain of pain and weakness, and may self-limit movement. Pain produces a decrease in the quality and quantity of movement which subsequently produces more pain, stiffness, and weakness and further destruction of arthritic joints. The therapeutic pool offers a unique environment in which patients can improve both the resistance to, and the assistance of, movement

Hypothesized Benefits
Decreased joint and soft tissue swelling, inflammation and/or restriction. Increased joint integrity and mobility. Improved quality and quantity of movement between and across body segments. Increased strength, power and endurance. Increased motor function (motor control and motor learning)

Hypothesis
Slower-velocity activity and exercise in an aquatic environment lead to:

  • Decreased joint and soft tissue swelling, inflammation and/or restriction
  • Increased joint integrity and mobility

Rapid-velocity activity and exercise in an aquatic medium lead to:

  • Increased strength, power and endurance

Mixed-velocity activity and exercise in an aquatic environment lead to:

  • Increased motor function (motor control and motor learning)
  • Improved quality and quantity of movement between and across body segments

Building an argument to support or negate hypothesis
I. Hydrodynamic principles
Immersed bodies are affected by the buoyancy, viscosity, and flow of the water in which they are immersed. These properties combine to create a therapeutic environment in which the rheumatology patient can be treated.

Buoyancy
Archimedes' principle states: "when a body is wholly or partially immersed in a fluid, it experiences an upthrust equal to the weight of fluid displaced." This upthrust, or buoyancy, counterbalances gravity and supports the body, resulting in an apparent reduction in weight bearing through the spine and lower extremities. Buoyancy can provide either assistance and support or resistance to movement of the body in the water, depending on the position of the individual.

Basically, buoyancy is an upward thrust which acts in the opposite direction to the force of gravity. Therefore, a body in water is subject to two opposing forces: gravity acting through a center of gravity (COG) and buoyancy acting through the center of buoyancy (COB). These forces, when not perfectly aligned, create a moment around a pivot point and the body rotates.

When discussing whether a body or body part immersed in water will sink or float, it is important to understand the concept of relative density (alternatively known as specific gravity).

Relative density is "the ratio of the mass of an object to an equal volume of water". Water has a specific gravity equal to 1. It serves as the reference point for all objects. Objects with relative density less than water float, and those with relative density greater than water sink. Objects with relative density near the value of water hover just below the surface.

The human body has elements which tend to sink (dense muscle) and elements which tend to float (fatty tissue and air-filled lungs). This tendency to float counterbalances gravity and supports the body, resulting in an apparent reduction in weight. This reduction in weight can provide relief from compressive forces on painful joints.

It is therefore possible for a person to stand, even walk, with reduced pain without external support or abnormal protective mechanisms in the water. Thus, the patient can initiate "normal" weight bearing tasks such as gait, transfers, and balance drills in the water and offset any deconditioning effects of immobility or reduced movement.

As already mentioned, the relative density of water has been arbitrarily set at 1 (RD = 1). It follows then that if an object has a relative density greater than 1, the object will sink.

There are many factors which will increase the relative density of an object:

  • spastic limbs;bulky muscular body;tense fearful patient;kyphotic trunk alignment;disproportionate higher and lower trunk size (hydrocephalus) disproportionate limb/trunk ratio (short legs, long trunk, lower center of gravity);
  • deflated lungs (RD = 1.05-1.084).

If relative density is less than 1, an object will float on the surface. There are many factors which decrease the relative density of an object: Ÿ

  • flaccid limbs; high adipose body;relaxed patient;
  • inflated lungs (RD = .95-.974).

So, how can "buoyancy" create a therapeutic environment? For one, exercise in water produces less spinal and lower extremity joint compression than the identical exercise performed on land. This reduction in compression creates an environment in which weight bearing and joint compression (of the lower extremities and spine) can be applied in a graded or progressive manner by the therapist.

In conclusion, buoyancy can be used to decrease the fight against gravity's downward thrust by producing:

  • a decrease in weight bearing through joints;a decrease in joint stress; a decrease in splinting or guarding of antigravity muscles;
  • an increase in freedom of movement.

Buoyancy can also promote ease of handling of the large or heavy patient, allow access to body parts which would be inaccessible if the patient was positioned on a plinth or chair, and allow progression of resistance in a logical, graded fashion, from:

  • buoyancy-assisted (easiest);buoyancy-eliminated (harder);
  • buoyancy-resisted (hardest).

Viscosity
Viscosity is nothing more than the inherent friction that exists between molecules of a liquid which cause a resistance to flow. Molecules of a liquid adhere to the surface of a body moving through that liquid resulting in resistance. When examining the qualities of viscosity, it is important to remember that:

  • resistance increases as viscosity increases; resistance to movement at a given velocity is greater in water than in air (fluid is more viscous than air);
  • viscosity decreases as temperature increases (the molecules separate).

It is possible to use viscosity therapeutically. Water is more viscous than air, and resistance to flow through water is greater than resistance to flow through air. Thus, it takes more force to push through water molecules than to push through air molecules.

Additionally, the faster an object is pushed through the water, the more turbulence is created and this creates additional resistance to movement.

Flow
When an object moves through a fluid, there is an increase in the pressure in the front of an object combined with a reduction in pressure in the back. This results in the water wanting to move from an area of high pressure to an area of lower pressure.

The area of "negative pressure" is known as the wake. Eddy currents form in this wake and "pull" the object back. The negative pressure (or drag) behind a moving object (the wake) is responsible for 90% of the impedance of movement. Surprisingly, the bow wave (the positive pressure in front of the object) is only responsible for 10% of the impedance.

In a streamlined flow of a liquid, a thin layer of fluid molecules slide over one another. Resistance is directly proportional to the velocity of movement and no eddy currents are created. In unstreamlined (turbulent) flow of a liquid, there is an irregular, rapid, random movement of fluid molecules. Resistance is directly proportional to the velocity of movement squared and eddy currents are created.

The principle of flow can be used therapeutically to increase (or decrease) the ease of movement by creating positive and negative drag. Resistance can be altered by:

  • varying velocity of movement; opposing inertia; altering streamlining; making quick reversals of flow (reversals in direction resulting in turbulence);
  • using rebound off the side of the pool.

It is also possible to use the concepts of flow to decrease resistance by taking advantage of the "pull" of wake or by performing movements in a more streamlined position.

II. Scientific research
Although the beginnings of a solid case can be made based on hydrodynamic principles alone, there has also been some research that has examined whether aquatic therapy can increase flexibility, strength, and movement quality/quantity in rheumatology patients.

Dial and Windsor examined the combined effects of an 8-week health education/water exercise class for 12 adults with rheumatoid arthritis. [1] Self-report tools indicated that the subjects had improved in functional status, pain, mobility, tenderness in joints, joint movement, number of recent flare-ups and treatment expectations. There was no significant improvement in ADL outlook. Objective findings showed significant improvement in the following: shoulder, elbow and wrist AROM, ability to flex digits to palmer crease, hip and knee AROM, and timed tests for arise-walk-sitting, walking 50 feet times, and donning-removal of shirt. The subjects did not show significant improvement in grip strength, morning stiffness, ankle AROM or MCP extension.

In a study by Danneskiold-Samsoe et al, subjects diagnosed with functional class II or III participated in an aquatic exercise program 2x/week for 2 months. [2] After 2 months of exercise participation, maximal isometric and isokinetic strength of the quadriceps increased by 38% and 16%, respectively.

Bacon et al examined the effects of an aquatic exercise program on individuals diagnosed with JRA (functional class I-III). [3] There were significant ROM improvements in bilateral hip internal rotation, and right hip flexion with knee extended. Trends toward increased plantar flexion ROM were also noted but not significant. There were no significant improvements in balance or timed tasks. There were no significant differences (although a trend was evident) toward increased gait cadence, velocity and stride length.

Templeton et al examined the objective changes in joint flexibility and functional ability in rheumatologic populations after participation in an aquatic therapy program. [4] Measurements of joint ROM and functional ability measured by the Functional Status Index (FSI) were determined pre- and post-aquatic exercise. Psychosocial factors were emphasized by encouraging members to share benefits, joys, and accomplishments prior to each class session. Following the eight week aquatic program, joint ROM measurements and functional ability (FSI) significantly improved. Aquatic therapy was identified as an effective treatment for improving quality of life in this population. There was no significant improvement in the subjects' ratings of "need for assistance" with daily functional tasks.

Stenstrom et al examined the effects of a 1x/week aquatic exercise class for 30 subjects with class II RA over a 4 year span. [5] After four years of training 1x/week, the following significant improvements were evident in the training group: grip strength, frequency of exercise and frequency of hospitalization in the Department of Internal Medicine. Additionally, the control group attended supplemental physiotherapy visits more often than the training group (34 visits and 21 visits, respectively). At the two-year follow-up, the training group remained significantly more active and more likely to exercise than the control group. A majority of the training group continued to independently perform intensive, dynamic water training even though this was not offered as a service through the study. All but one subject in the training group rated the long-term benefits of the 1x/week training as "important" or "rather important."

Jentoft et al [6] examined the effects of pool-based (PE) and land-based (LE) exercise programs on patients with fibromyalgia. The outcomes were assessed by the Fibromyalgia Impact Questionnaire, the Arthritis Self-Efficacy Scale, and tests of physical capacity. After 20 weeks, greater improvement in grip strength was seen in the LE group compared with the PE group, although both improved. The results were mainly unchanged at 6 months follow-up.

Green and colleagues [7] assessed the treatment effectiveness of home exercise alone versus the effectiveness of home exercises plus hydrotherapy for osteoarthritis of the hip. The authors examined range of motion (goniometry) muscle strength (dynamometry), and functional abilities (transfer times, walking speed and number of steps required for a fixed distance, and stairclimbing/descent speeds). Weeks 0-6 were used to establish a baseline. There was no significant difference of any parameters over this period. Weeks 9-12 were used to examine treatment effects compared to the baseline information. 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 6 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 elements most effected by both interventions were joint stiffness, hip external rotation, hip abduction power/endurance, the number of steps necessary to travel a distance and to ascend/descend a set of steps. 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.

Conclusion
This column attempts to establish the beginning of a hydrodynamic and scientific basis for the use of aquatic therapy to improve the strength, flexibility and quality and quantity of movement in patients with rheumatology disorders.

References
1. Dial C, Windsor RA. A formative evaluation of a health education-water exercise program for class II and class III adult rheumatoid arthritis patients. Patient Educ Counsel. 1985; 7: 33-42.

2. Danneskiold-Samsoe B, Lyngberg K, Risum T, Telling M. The effect of water exercise therapy given to patients with rheumatoid arthritis. Scand J Rehabil Med . 1987; 19(11): 31-35.

3. Bacon MC, Nicholson C, Binder H, White PH. Juvenile rheumatoid arthritis: aquatic exercise and lower-extremity function. Arthritis Care Res. 1991; 4(2): 102-105.

4. Templeton MS, Booth DL, O' WD. Effects of aquatic therapy on joint flexibility and functional ability in subjects with rheumatic disease. J Orthop Sports Phys Ther. 1996; 23(6): 376-381.

5. Stenstrom CH, Lindell B, Swanberg E, Swanberg P, Harms-Ringdahl K, Nordemar R. Intensive dynamic training in water for rheumatoid arthritis functional class II - a long-term study of effects. Scand J Rheumatol. 1991; 20: 358-365.

6. Jentoft ES, Kvalvik AG, Mengshoel AM. Effects of pool-based and land-based aerobic exercise on women with fibromyalgia/ chronic widespread muscle pain. Arthritis Rheum. 2001; 45(1): 42-47.

7. Green J, McKenna F, Redfern EJ, Chamberlain MA. Home exercises are as effective as out-patient hydrotherapy for osteo-arthritis of the hip. Br J Rheumatology. 1993; 32(9): 812-815.


Part III

Throughout this five-part series, we will test the idea that aquatic therapy is an effective treatment for the impairments, functional limitations and disabilities commonly associated with rheumatic diseases.

Building a Case for Treating Rheumatologic Patients with Aquatic Therapy
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
Decreased pain. 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 required 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

2) 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

3) 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

4) 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;

5) 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 5 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 2x/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 6 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 (ten-point pain scale) over baseline in patients who participated in a 45-minute, 2x/week, 8-week aquatic exercise class taught in 91d Fahrenheit water.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 over 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.

References
1 Whitney SL. Physical agents: heat and cold modalities. In: Scully RM, Barnes MR. Physical Therapy. Philadelphia, PA: JB Lippincott Company; 1989:856-857.

2 Christie JL, Sheldahl LM, Tristani FE, Wann LS, Sagar KB, Vevandoski SG, Ptacin MJ, Sobocinski KA, Morris RD. Cardiovascular regulation during head-out water immersion exercise. J Appl Physiol. 1990;69(2):657-664.

3 Sagawa S, Shiraki K, Yousef MK, Konda N. Water temperature and intensity of exercise in maintenance of thermal equilibrium. J Appl Physiol. 1988;65(6):2413-2419.

4 Walsh M. Hydrotherapy: the use of water as a therapeutic agent. In: Michlovits SL, Wolf S (eds). Thermal Agents in Rehabilitation. Philadelphia, PA: FA Davis Company; 1986:119-139.

5 Michlovitz SL. Biophysical principles of heating and superficial heat agents. In: Michlovits SL, Wolf S (eds). Thermal Agents in Rehabilitation. Philadelphia, PA: FA Davis Company; 1986:99-118.

6 Whitney SL. Physical agents: heat and cold modalities. In: Scully RM, Barnes MR (eds). Physical Therapy. Philadelphia, PA: JB Lippincott Company; 1989:848-849.

7 Warren CG. The use of heat and cold in the treatment of common musculoskeletal disorders. In: Kessler RM, Hertling D. Management of Common Musculoskeletal Disorders. Philadelphia, PA: Harper and Row; 1983.

8 Green J, McKenna F, Redfern EJ, Chamberlain MA (research article). Goldby LJ, Scott DL (editorial). Home exercises are as effective as outpatient hydrotherapy for osteoarthritis of the hip. British Journal of Rheumatology. 1993;32(9):812-815 and editorial, 771-773 (The way forward for hydrotherapy).

9 Meyer CL, Hawley DJ. Characteristics of participants in water exercise programs compared to patients seen in a rheumatic disease clinics. Arthritis Care Res. 1994;7(2):85-89.

10 Templeton MS, Booth DL, O'Kelly WD. Effects of aquatic therapy on joint flexibility and functional ability in subjects with rheumatic disease. J Orthop Sports Phys Ther. 1996;23(6):376-381.

11 McNeal RL. Aquatic therapy for patients with rheumatic disease. Rheum Dis Clin North Am. 1990;16(4):915-929.

12 Stein PN, Motta RW. Effects of aerobic and nonaerobic exercise on depression and self-concept. Percept Mot Skills. 1992; 74(1): 79-89.

13 Dua J, Hargreaves L. Effect of aerobic exercise on negative affect, positive affect, stress, and depression. Percept Mot Skills. 1992; 75(2): 355-361.

14 Coyle CP, Santiago MC. Aerobic exercise training and depressive symptomatology in adults with physical disabilities. Arch Phys Med Rehabil. 1995; 76(7): 647-652.

15 Byrne A, Byrne DG. The effect of exercise on depression, anxiety and other mood states: a review. J Psychosom Res. 1993; 37(3): 565-574.

16 Moore KA, Blumenthal JA. Exercise training as an alternative treatment for depression among older adults. Altern Ther Health Med. 1998; 4(1): 48-56.

17 Liska K. Drugs and the Human Body: Implications for Society. 2nd ed. New York: Macmillan Publishing Company; 1986:117-118


Part IV

Throughout this five-part series, we will test the idea that aquatic therapy is an effective treatment for the impairments, functional limitations and disabilities commonly associated with rheumatic diseases.

Building a Case for Treating Rheumatologic Patients with Aquatic Therapy
Balance reactions and other proprioceptive tasks are trainable in patients with rheumatological conditions. Improvement in balance is caused by the ability to make movement errors and correct for them and the water provides an environment in which this can be attempted safely.

Hypothesized benefits
I mproved balance. Improved sensory awareness.

Hypothesis
Patients may be challenged beyond limits of stability in the water without the fear of consequences of falling which are often present with land-based balance training. The environment leads to improvement in balance reactions which are translatable to land.

Building an Argument
I. Hydrodynamic principles
Movement through water is affected by turbulence and viscosity. Water is more viscous than air, and resistance to flow through water is greater than resistance to flow through air. Thus, it takes more force to push through water molecules than to push through air molecules. Additionally, the faster an object is pushed through the water, the more turbulence is created and this creates additional resistance to movement.

Richley Geigle et al argue that somatosensory input is increased more by moving an object through a viscous liquid than by moving through a less viscous gas (air). They postulate that resistance to movement may "cause distention or stretch of the skin resulting in stimulation of rapidly adapting mechanoreceptors, perhaps contributing to better proprioception."1

A body immersed is surrounded by a viscous fluid which retards the speed of movement. This viscosity prevents rapid falling and elongates the period of time in which a patient can respond to a shift of his center of mass outside his base of support.

Additionally, the natural end result of a loss of balance which is not corrected is a fall into a compliant fluid (water) and not a fall to a noncompliant solid (the ground). Thus, the patient may be challenged to move outside his base of support without fear of traumatic consequences.

This reduction in patient anxiety may encourage the patient to attempt tasks which he would not attempt on land. It becomes possible to elicit balance challenges which the patient has both time and mental confidence to combat. On land, without the assistance of such aquatic properties, the resultant balance responses may be incomplete or absent.

Water offers a three dimensional environment of both support and resistance. Any object with a specific gravity of less than one will tend to float toward the surface of the water. Alternatively, any object with a specific gravity less than one will sink.

According to Richley Geigle et al, these forces combine to "create multiple combinations of joint angles and planes of motion which are assisted, supported or resisted to various degrees. The therapist may use these combinations in the water to challenge the patient beyond his or her limit of stability, without the fear of the consequences of falling which are often present with land-based balance training."1

II. Clinical Research
Simmons and Hansen tested the effects of exercise, immersion in water, socialization and a combination of all these factors on balance control.2 Subjects were divided into four groups: water sitters, land sitters, water exercisers and land exercisers. These four groups were created to attempt to isolate the factors which improve gait: exercise alone (land exercise), water immersion (water sitting), socialization (land sitting) or exercise in a medium which permitted multiple "movement errors" without fear of falling (water exercise). All groups met for 45 minutes, 2x/week for five weeks with the supervision/instruction of a physical therapist. Exercise in the water enhanced the functional reach (FR) of the subjects more than did socialization, water immersion or exercise alone. FR improved over 35 cm by week five and resulted in continued participation in exercise, no orthopedic injuries and some subjects discarding their assistive gait devices.

Conclusion
In addition to the above, Simmons and Hansen found that the water exercisers adhered to their program, as evidenced by better attendance rates. The authors postulate that the improvement shown by the water exercisers was due to their ability to make and correct for movement errors in a viscous, safe environment which provided proprioceptive feedback to movement. The authors felt that land-based exercise may be too intimidating for those with balance deficits; the cost of loss of balance is much greater than it is in water. The water's turbulence, inherent destabilizing effect, and depth-dependent buoyancy effect may enhance the variability of practical effect needed to learn compensation for loss of balance.

References
1. Geigle, P.R., Cheek, W.L., Gould, M.L., Hunt, H.C., & Shafiq, B. (1997). Aquatic physical therapy for balance: The interaction of somatosensory and hydrodynamic principles. Journal of Aquatic Physical Therapy, 5(1), 4-10.

2. Simmons, V., & Hansen, P.D. (1996). Effectiveness of water exercise on postural mobility in the well elderly: An experimental study on balance enhancement. Journal of Gerontology, 51A(5), M233-M238.


Part V

Throughout this five-part series, we will test the idea that aquatic therapy is an effective treatment for the impairments, functional limitations and disabilities commonly associated with rheumatic diseases.

Building a Case for Treating Rheumatologic Patients with Aquatic Therapy
Consistent physical exercise is an effective intervention for the management of immunologic disorders. However, load-bearing during physical exercise may actually lead to an exacerbation of pain and joint degeneration in patients with immunologic disorders. It is possible to exercise in the pool without this load-bearing, thus allowing greater participation in weight-bearing activities.

Hypothesized Benefits
Reduction in weight bearing during standing. Ability to progressively increase weight bearing.

Hypothesis
Exercise in water produces less spinal and lower extremity loading than the identical exercise performed on land. This reduction in weight bearing results in a secondary reduction in motor activity required from postural muscles.

Building the Case
1. Hydrodynamic principles
Archimedes' principle states: "when a body is wholly or partially immersed in a fluid, it experiences an upthrust equal to the weight of fluid displaced."1 Water has a relative density (specific gravity) equal to 1. It serves as the reference point for all objects.

Objects with specific gravity less than water float, and those with specific gravity greater than water sink. Objects with specific gravity near the value of water hover just below the surface. The human body has elements which tend to sink (dense muscle) and elements which tend to float (fatty tissue and air-filled lungs).

This tendency to float counterbalances gravity and supports the body, resulting in an apparent reduction in weight. This reduction in weight can provide relief from compressive forces on painful joints. It is therefore possible for a person to stand, even walk, with reduced pain without external support or abnormal protective mechanisms in the water. Thus, the patient can initiate "normal" weight bearing tasks such as gait, transfers ,and balance drills in the water and offset any deconditioning effects of immobility or reduced movement.

II. Clinical research
Muscle activity may be systematically reduced by increasing the amount of the body submerged. Mano et al examined the effects of graded immersion on skin and muscle receptors during quiet standing.2 Mano and his team examined the effects of immersion in warm water on muscle sympathetic activity (MSA) and electromyography (EMG) of the soleus muscle, and skin sympathetic activity (SSA) of the sole of the foot.

As the level of immersion increased, both MSA and EMG activity decreased proportionally as weight bearing diminished. With immersion to the cervical spine, both MSA and EMG became almost absent. In other words, the subjects' calf muscles became less active in a buoyant environment. In effect, the calf muscle responsible for maintaining upright posture in a gravity-based environment had diminished responsibilities.

Additionally, as the level of immersion was increased, the sympathetic activity of the skin on the sole of the foot decreased. With immersion to the cervical spine, the SSA showed a marked and proportional decrease in activity. Translated, this means that although immersion results in less motor activity for postural muscles such as the calf, it also results in less sensory input to the skin (and probably joint) receptors which record weight bearing.

Weight bearing may be systematically reduced by increasing the amount of the body submerged.3,4 A study by Harrison and Bulstrode measured static weight bearing in a pool using a population of healthy adults.3 Results indicated that weight bearing during immersion was reduced to less than land-based weight. Immersion to C-7 levels reduced weight bearing to 5.9%-10% of actual total body weight. Immersion to the xiphosternum reduced weight bearing to 25%-37% of actual total body weight. Immersion to the level of the anterior superior iliac spine (ASIS) reduced weight bearing to 40%-56% of actual total body weight. The researchers reported that variations in gender, physical build and body composition of subjects only minimally effect weight bearing values.

A follow-up study by Harrison, Hillma, and Bulstrode compared weight bearing during immersed standing, slow and fast walking.4 During static standing, immersion to the groin resulted in up to a 25% reduction of weight bearing. When immersed to the mid-trunk, subjects experienced between a 25-50% reduction in weight. When immersed to the clavicle, weight bearing was reduced to between 50-75% of normal. Immersion above the clavicle resulted in almost complete loss of weight bearing.

During slow walking, subjects had to be immersed to the ASIS before weight bearing was reduced to 75% of normal. When immersed to mid-trunk during slow walking, weight was further reduced to 50-75% of normal. Immersion to the clavicle during slow walking reduced weight bearing up to 50% of normal values, and immersion above the clavicle resulted in weight bearing 25% of normal or less.

During fast walking, mid-trunk immersion produced weight-bearing up to 75% of actual weight. Subjects had to be immersed deeper than the xiphosternum during fast walking in order for weight bearing to be less than 50% and deeper than C-7 for weight bearing to be less than 25% of normal values. Harrison, Hillma and Bulstrode warn clinicians to be especially cautious during rapid water walking which can produce up to 50% weight bearing even when the patient is immersed to the xiphosternum. Results from their 1992 study showed that the percent weight bearing during walking was much higher (up to 76% higher) than static standing at the same immersion level.

Conclusion
Many researchers credit the aquatic environment for providing a reduced-load bearing environment in which to work.

Weinstein reported that reduced joint compression and reaction forces were partially responsible for symptom reduction in a population of adults with various forms of arthritis who participated in a group aquatic exercise class.5

McNeal suggested that buoyancy provides an environment which allows for decreased muscle activity promoting muscle relaxation as well as decreased joint compression.6 It is evident that patients with rheumatic complaints may find the water a safe and comfortable environment in which to work.

References
1 Edlich R.F., Towler M.A., Goitz R.J., Wilder R.P., Buschbacher L.P., Morgan R.F., Thacker J.G. Bioengineering principles of hydrotherapy. (1987). J Burn Care Rehabil. 8(6):580-584.

2 Mano T., Iwase S., Yamazaki Y., Saito M. Sympathetic nervous adjustments in man to simulated weightlessness induced by water immersion. (1985). Sangyo Ika Diagaku Zasshi. 7 (Suppl): 215-227.

3. Harrison R.A., Bulstrode S. Percentage weight bearing during partial immersion in the hydrotherapy pool.(1987). Physiother Practice. 3: 60-63.

4. Harrison R.A., Hillma M., Bulstrode S. Loading of the lower limb when walking partially immersed: implications for clinical practice. (1992). Physiotherapy. 78(3): 164-166.

5. Weinstein L.B. The benefits of aquatic activity. (1986). J Gerontol Nurs. 12(2):7-11.

6. McNeal R.L. (1990). Aquatic therapy for patients with rheumatic disease. Rheum Dis Clin North Am. 16(4):915-929.

Disclaimer
The information presented in this article is meant to be a summary and educational in nature. It is not meant to serve as a substitute for legal advice.

Author Bio
Andrea Poteat Salzman, MS, PT is the owner of two businesses, the Aquatic Resources Network and Concepts in Physical Therapy. She has received both the prestiguous Aquatic Therapy Professional of the Year Award (Aquatic Therapy and Rehabilitation Institute) and the Tsunami Aquatic Therapy Award.

Salzman is well-regarded within the industry as:

  • Editor-in-Chief of an aquatic therapy trade journal and newsletter;
  • Author of over a dozen publications, including the soon-to-be-released Evidence-Based Aquatic Therapy textbook;
  • Freelance author and columnist;
  • Aquatic therapy seminar instructor;
  • Adjunct faculty and research advisor, St. Catherine Physical Therapy Program, Minneapolis, MN;
  • Immediate past manager of therapeutic aquatics, St. Paul Ramsey Medical Center, St. Paul, MN;
  • Researcher and grant recipient examining aquatic exercise vs. land-based exercise.

She may be reached via e-mail at asalzman@aquaticnet.com

 


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