We have all read books and articles extolling (sans references) the virtues of aquatic therapy. This is unfortunate. In order to be taken as credible witnesses regarding the benefits of aquatic intervention, we must first remove ourselves from the rank and file of the cheerleader and plop ourselves unceremoniously into the role of devil's advocate.

This is particularly important for our patients with spinal disorders as it is often exceptionally difficult to tease out etiology and mechanism of dysfunction.I am a believer in the virtues of aquatic physical therapy (count me convert), but only for the right patients with the right aquatic interventions.

Before selecting this treatment option for any of your patients with spinal dysfunction, ask yourself the following.

Aquatic Therapy Checklist:[1]
1. Have I established that the patient has impairments and/or functional limitations which may be positively affected by therapy?

2. Have I established that the patient requires skilled intervention in order to diminish these deficits?

3. Have I established that water offers a therapeutic environment for the performance of these interventions which is unachievable on land?

4. Have I established that the evidence (scientific research) has demonstrated benefits with aquatic physical therapy for this type of patient?

Question 1. Does the patient have impairments, functional limitations and/or disabilities which may be positively affected by therapy?
First, you must determine if the patient's condition can even be altered by intervention. The American Physical Therapy Association created The Guide to Physical Therapy Practice: Part II: Preferred Practice Patterns which is of singular use in tackling this question.[2]

In the Guide you can look for the pattern which best describes your patient to determine if its associated impairments and functional limitations may be positively affected by therapy. If the answer is yes, continue to question 2.

If the answer if no, the patient should not be seen for any intervention, aquatic or land-based. (Note: one exception to this would be a limited number of sessions designed to educate the patient to self-treat his dysfunction).

Question 2. Does the patient requires skilled intervention in order to diminish deficits?
Once it has been established that the patient has impairments or functional limitations which may be altered by physical therapy, it then become important to ask: Do the patient's problems require a licensed provider? The hallmark of professionalism is the ability to provide the best care with the least depletion of valuable resources. Not all patients require skilled care in order to get better. In order to determine if your patient requires skilled intervention to diminish his deficits, ask yourself these questions:[4] Does the patient require an:

• Individualized examination in order to determine a diagnosis, prognosis, and interventions? Individualized program of therapeutic interventions to alleviate impairments and functional limitations?
• Individualized program for prevention of injury, impairment, functional limitation and/or disability?

It is sometimes helpful to ask yourself: If I was referring this patient for land-based treatment for these same deficits, would I refer to 1:1 PT or to a health club or group class setting?

Question 3. Does water offers a therapeutic environment which is unachievable on land?
The water offers a unique therapeutic environment which can be harnessed by a skilled provider to permit activities unachievable on land. In water, weight bearing of the lower extremities and spine can be reduced or eliminated by buoyancy, pain can be reduced by the application of superficial heat, proprioceptive input can be enhanced by viscosity and turbulence, and the pain cycle can be interrupted by offloading the spine and buffeting the body with sensory input.It is both difficult and clinically impractical to achieve these effects on land.

1. Application of weight bearing in graded or progressive manner

Hypothesis: 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.

Argument: 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."[5] This upthrust, or buoyancy, counterbalances gravity and supports the body, resulting in an apparent reduction in weight bearing through the spine and lower extremities.[6] Buoyancy can provide either assistance and support or resistance to movement of the body in the water, depending on the position of the individual.[7] Weight bearing may be systematically reduced by increasing the amount of the body submerged.[8,9]

A study by Harrison and Bulstrode measured static weight bearing in a pool using a population of healthy adults.[8] Results indicated that weight bearing during immersion was reduced to less than land-based weight. Immersion to C-7 levels reduced weight to 5.9%-10% of normal weight. Immersion to the xiphosternum reduced weight to 25%-37% of normal. Immersion to the level of the anterior superior iliac spine (ASIS) reduced weight to 40%-56% of normal.

A follow-up study by Harrison, Hillma, and Bulstrode compared weight bearing during immersed standing, slow and fast walking.[9] During slow walking, subjects had to be immersed to the ASIS before weight bearing was reduced to 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 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.

2. Decrease in subjective complaints

Hypothesis: Aquatic therapy performed in a therapeutic pool provides a palliative effect and may reduce these complaints. Argument : Although dependent on the population using the facility, therapeutic pools are generally heated to between 92 and 97 degrees Fahrenheit.[10]

At temperatures above "thermoneutral" (approximately 93-95 degrees F at rest and 91-92 degrees F during mild exercise),[11,12] body temperature increases due to the reduced ability of the body to dissipate heat through the skin.[13,14] Thermal energy (heat) is exchanged between water and the body and between air and the body.

Energy exchange between a submerged body and the water occurs through both convection and conduction. 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.[13]

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.[14]

The mechanism of pain relief may come from one of several phenomena discussed in great detail in the July, 1997 issue of the Journal of Aquatic Physical Therapy [15]

3. Movement-induced enhancement of somatosensory input (improved proprioceptive input)

Hypothesis: Movement of a body part through water results in greater somatosensory input to receptors than movement of that body part through air. Argument : Movement through water is affected by turbulence and viscosity.[5] 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 and colleagues argue that somatosensory input is increased more by moving an object through a viscous liquid than by moving through a less viscous gas (air).[16] 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."[16]

4. Interruption of pain cycle

Hypothesis: Standing in water results in less spinal and lower extremity weight bearing than standing on land. This reduction in weight bearing results in a reduction in motor activity required from postural muscles. This reduction in motor activity allows patients to maintain an upright, stable position with less muscle spasm.

Argument: 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."[5] 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.[7]

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.

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.[17] 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.

Question 4. Has the evidence (scientific research) demonstrated benefits with aquatic physical therapy for this type of patient?
The short answer is yes. Barely. Although there exist several studies on the beneficial effects of aquatic physical therapy for patients with spinal dysfunction [18-27], this area of research lags far behind work done on other populations, such as rheumatology. As a detailed discussion of the scientific literature is beyond the space constraints of this article, readers are directed to the primary research and to the text Prove It! Justifiable Aquatic Therapy [28] for more detailed discussions on this topic.

References
1. Poteat Salzman A. Prove It! Justifiable Aquatic Therapy East Hampstead, NH: Northeast Seminars lecture series; 1998.

2. American Physical Therapy Association. The Guide to Physical Therapy Practice: Part II: Preferred Practice Patterns. Phys Ther 1997;77(11):1227-1619.

3. American Physical Therapy Association (APTA) Aquatic Physical Therapy Section. Statement of Purposes, Rationale, and Goals Alexandria, VA: APTA; 1992.

4. American Physical Therapy Association. The Guide to Physical Therapy Practice: Part I: Description of Patient/Cleint Management. Phys Ther 1997;77(11);1178.

5. Edlich RF, Towler MA, Goitz RJ, Wilder RP, Buschbacher LP, Morgan RF, Thacker JG. Bioengineering principles of hydrotherapy. J Burn Care Rehabil 1987;8(6):580-584.

6. Cirullo JA. Aquatic physical therapy approaches for the spine. Orthop Phys Ther Clin North Am 1994;3(2):179-208.

7. Styer-Acevedo J, Cirullo JA. Integrating land and aquatic approaches with a functional emphasis. Orthop Phys Ther Clin North Am 1994;3(2):165-178.

8. Harrison RA, Bulstrode S. Percentage weight bearing during partial immersion in the hydrotherapy pool. Physiother Practice 1987;3:60-63.

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

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

11. 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.

12. 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.

13. 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.

14. 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.

15. Poteat AL, Bjerke MD, Johnston TD, Mairs JP. Evidence-based aquatic therapy: Building a case for use of aquatic physical therapy for fibromyalgia patient populations. J Aquatic Phys Ther 1997;5(2): 8-16.

16. Richley Geigle P, Cheek WL, Gould ML, Hunt HC III, Shafiq B. Aquatic physical therapy for balance: the interaction of somatosensory and hydrodynamic principles. J Aquatic Phys Ther 1997;5(1):4-10.

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

18. Guillemin F, Constant F, Collin JF, Boulange M. Short and long-term effects of spa therapy in chronic low back pain. Br J Rheumatol 1994;33(2):148-151.

19. Konrad K, Tatrai T, Hunka A, Vereckei E, Korondi I. Controlled trial of balneotherapy in treatment of low back pain. Ann Rheum Dis 1992;51(6):820-822.

20. Langridge JC, Phillips D. Group hydrotherapy exercises for chronic back pain sufferers - introduction and monitoring. Physiotherapy 1988;74:269-273.

21. Lefort SM, Hannah TE. Return to work following an aquafitness and muscle strengthening program for the low back injured. Arch Phys Med Rehabil 1994;75(11):1247-1255.

22. Cunha MC, Oliveira AS, Labronici RH, Gabbai AA. Spinal muscular atrophy type II (intermediary) and III (Kugelberg-Welander). Evolution of 50 patients with physiotherapy and hydrotherapy in a swimming pool. Arq Neuropsiquiatr 1996;54(3):402-6.

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