Physical Therapist and Watsu Instructor

Lieb has written an in-depth paper containing a wealth of information. This paper is comprised of three sections. The first section describes the physiological responses of the body during a hypothetical Watsu session. The second section begins with "Structure and Function of the Three Fluid Systems." This section is committed to a review of the anatomy and physiology of the circulatory, lymph and renal systems with an emphasis on the circulatory system. The final section begins with "The Action of Water and Shiatsu on the Circulation."

It primarily restates the information from the first section of the paper and elaborates on some points with additional information. For the practitioner not familiar with medical terminology, it may be necessary to keep a medical dictionary close by. The middle section, in particular, is crammed with detailed and technical information which, though interesting and informative, is primarily background information which illuminates our understanding of the circulatory, lymph and renal systems. Practitioners will find the first and last sections of the paper more useful.

When reading this paper, it is important to remember that very little Watsu-specific research has been done. Therefore, many of the statements made here regarding physiological responses to Watsu are assumptions and conclusions drawn from other areas of research. While there is strong evidence to support many of Lieb’s points, some points are based on information which may just as easily lead to different conclusions. Additionally, some research in water immersion has led to conflicting results. While all of this is important to keep in mind, it does not detract from the value of Lieb’s paper. It gives the reader an firm base from which to begin to understand the physiological responses to Watsu, and shines light on areas needing further research.

There are a few areas where Lieb’s paper needs comment or clarification. For example, Lieb states that heart rate increases along with stroke volume during immersion. Although research studying heart rate during immersion shows some conflicting results, heart rate response to water temperature appears to be fairly consistent. At 25° C, heart rate does not increase, but instead drops by approximately 12-15 bpm . In thermoneutral water of 34° C, heart rate decreases less, but still drops (1,2). It is only in very warm water that heart rate increases (3,4). Cardiac output, on the other hand, always increases with immersion in water (5). Increased cardiac output is secondary to the 700 ml increase in central blood volume which increases cardiac volume by 27-30% with immersion to the neck (1,6). The increased blood volume in the heart stretches the myocardium and thereby improves the actin-myosin filament relationship and results in a stronger contraction (3). This causes an increase in end-diastolic volume, and a decrease in end-systolic volume. Stroke volume increases an average of 35% with immersion to the neck (6). In other words, the heart pumps more efficiently by filling more completely and emptying more completely, and therefore pumps more blood with each contraction. Because more blood is pumped with each beat, the heart doesn’t need to beat as frequently, and this is why heart rate drops in cool and thermoneutral temperatures. In thermoneutral temperature of 34-35° C, as is maintained in most Watsu pools, heart rate decreases and cardiac stroke volume increases. Although heart rate decreases, the net effect is still an increase of more than 30% in cardiac output (3). (Cardiac output is the product of stroke volume times pulse rate per unit of time.)

Although Lieb recommends 34°-35° C water for Watsu, he sometimes casually interchanges the terms thermoneutral water and body temperature water as though they are the same. It’s important to keep in mind the difference between the two. Thermoneutral temperature refers to water at a temperature which neither raises nor lowers core body temperature. Only 20% of the energy humans convert from food is used to do work. The remaining 80% is converted into thermal energy. If our bodies could not dissipate this heat, our core temperature would raise 3° C per hour during light activity. If our 37° C bodies are in 37° C water, we can’t dissipate heat, and our core body temperature rises (7). Therefore, body temperature water is not thermoneutral. 34°-35° C is thermoneutral for most people during a Watsu, but would not, for example, be thermoneutral for water aerobics. Also, the client’s condition or the external environment may necessitate a different water temperature. A client with multiple sclerosis may respond better to a cooler water temperature (8). A pool environment with very dry or very cool air temperatures may dictate a slightly higher water temperature.

Lieb also states that hydrostatic pressure is responsible for the 700ml increase in central blood volume. Other researchers conclude that buoyancy is at least an equal factor. They note that blood volume centralisation occurs regardless of the position of the body in water, even when upside down where the hydrostatic pressure gradient is reversed (9,10). Interestingly, blood volume centralisation also occurs in astronauts in space where there is no pressure differential. This suggests that buoyancy, which reduces the effects of gravity, plays a key role in blood volume centralisation (11).

In describing the renal response to immersion, Lieb elaborates on how the antidiuretic hormone (ADH) is suppressed resulting in an increase in urine production. It’s important to note that this response increases as the duration of immersion increases up to three hours, and then it slowly begins to taper off (12). This is of great significance for Watsu practitioners and all others who spend long hours in the aquatic environment. It is also important to note that atrial natriuretic peptide (ANP) is increased which contributes somewhat to diuresis by decreasing sodium reabsorption in the distal renal tubular system, but more importantly, increased ANP causes a suppression of thirst (13,14). The increase in urine production coupled with the suppression of thirst can lead to significant dehydration, especially in clients who are medically at risk and practitioners who spend long periods of time in the water.

Lieb refers to the decrease in tension in the antigravity muscles secondary to the gravity counter-balancing effect of buoyancy. Although this is true, there is also a decrease in muscle tone throughout the body’s muscles because of several additional factors. One of the most important of these factors is Watsu’s influence on the Autonomic Nervous System (ANS). Watsu has a balancing effect on the (ANS) causing a quieting of the Sympathetic Nervous System (SNS) and an enhancement of the Parasympathetic Nervous System (PNS). (15,16) This leads to multiple benefits for clients, not the least of which is a dramatic decrease in muscle tone (17). This decrease in muscle tone is of great significance to able-bodied clients suffering the effects of daily life stress as well as clients with special needs. Clients with orthopedic impairments experience a decrease in muscle spasm which provides pain relief. Clients with neurologic impairments experience a decrease in muscle tone which leads to a decrease in hypertonicity and spasticity.

Watsu’s rhythmical, gentle rocking motions combined with repeated trunk rotation and trunk elongation further help to decrease muscle tone. (18) Virtually all areas of neurorehabilitation, including Neurodevelopmental Treatment (NDT and also known as Bobath) and Brunnstrom, recognize the value of trunk rotation in decreasing excessive muscle tone in the trunk, shoulders, hips and also the extremities. Proprioceptive Neuromuscular Facilitation (PNF) also incorporates rotation into all activities as the key element in facilitating normal patterns of movement. (19) Watsu utilizes both static rotational stretches for the trunk and rhythmical, repeated trunk rotation in many of its commonly used movements. These include the most basic Watsu movements of Rotating Accordion and both Near and Far Leg Rotation.

The vestibular system also has a powerful influence on muscle tone. Work done in Sensory Integration supports the muscle tone reducing benefits of the slow, rhythmical, repeated movements used throughout a Watsu session. (20) These movements gently stimulate the vestibular system causing a dampening effect on muscle tone. However, overstimulation of the vestibular system may have the opposite effect, and care must be taken during a Watsu session to monitor the system. (8,21)

Watsu’s influence on the Autonomic Nervous System (ANS) may reach even farther in helping our clients. As more is learned about the adverse effects of ANS imbalance, many propose that ANS imbalance is the basis for numerous disease processes and impairments. These impairments range from fibromyalgia to reflex sympathetic dystrophy to post traumatic stress disorder and many more. (12,22) Clients experiencing ANS imbalance are often trapped in their fight/flight/freeze response which creates a physiological imbalance similar to pushing on the accelerator and the brake simultaneously. (23) Watsu has been used to help people move beyond the fight/flight/freeze response and onto a healthier life by helping to rebalance the

ANS. (1)

Through its wide range of effects, both physical and emotional, Watsu has far reaching benefits. It can help address many of our needs as humans, and improve our quality of life.

References

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By Peggy Schoedinger