Paul Chek

How many of you work with clients that complain of musculoskeletal pain? Knowing that many of you probably said "yes", how many of you are aware of the tremendous physiological benefits pool therapy can offer your clients to help them reduce pain and speed recovery? Today, many exercise professionals have access to a pool in their gym or clinic, yet are unaware of the many physiological benefits available to them and their clients through the use of pool therapy.

In this article, I will share the C.H.E.K Institute’s model of corrective exercise and a few of the many benefits available to you through the use of pool therapy (also known as aqua therapy, water therapy and/or hydrotherapy). The benefits of pool therapy that will be expanded on include:

  • Facilitated Venous Return
  • Sensory Modulation of Pain
  • Therapeutic Decompression


At the C.H.E.K Institute, we use a four-stage approach to recover from an injury. If the spine or any weight bearing joint is injured, we begin our corrective exercises in Phase I. This phase is achieved by eliminating axial load on the body or injured tissue during exercise. With the exception of certain extremity injuries, exercises are performed in a horizontal position, using an unweighted exercise system, or using the buoyancy created by water.

There should not be any increase in pain while exercising in Phase I. Although many Phase I clients begin their training session in pain due to the fact that they are injured, an agreement should be made at the beginning of each corrective exercise session that any escalation of pain beyond a predetermined level of discomfort will be reported immediately. Successful application of the principles presented here will result in the ability to complete an exercise session without any increase in pain. Ideally the client will experience a reduction in pain and an improved physiological status by the end of the training session.

Pool therapy is of great value for decreasing pain and improving your client’s recovery rate during Phase I (Table 1-A & 1-B). When any joint, ligament or muscle/tendon complex is injured, the pain-spasm cycle is activated. Depending on the severity of the injury, the inflammatory process will be synergistic with the markers of functional disability as indicated in Table 1-A.

Table 1A & 1B

To appreciate the many benefits of therapeutic intervention using pool therapy, let us investigate some of the key physiological affects provided by submersion and hydrotherapeutic stimulation.


During an acutely painful event, swelling appears in concert with circulatory stasis (Figure 1). As demonstrated in Figure 2, the athlete that continues loading an injured joint or tissue will progressively aggravate the injured tissue, which will significantly slow the recovery process. The persistent presence of pain inhibits the surrounding musculature, disrupting functional muscle contraction, which facilitates the pain-spasm cycle and disrupts the muscles ability to perform as a venous pump. The accumulation of metabolites further sensitizes nociceptors (pain receptors) which perpetuates the pain-spasm cycle and slows recovery (Figure 2 & Table 1-B).

Figure 1
The traumatic painful event with associated swelling and inflammation.

Figure 2

In Figure 3, the injured athlete is floating in water as he moves his leg freely. The hydrostatic pressure acts to assist the musculature in providing venous return, therefore enhancing circulation and diminishing the pain-spasm cycle (see Table 1B). By improving circulation, the healing process is improved via an increase oxygen and nutrient delivery to the affected tissue.

Figure 3


When weightbearing is painful and motion is limited due to pain and spasm, there is a great deal of nociceptive (pain) input to the spinal cord (Figure 4-A). While moving the injured segment in water, there is stimulation of sensory receptors in skin by the water as it passes by. The improved movement afforded in the pool environment increases stimulation from mechanoreceptors in the involved joint and surrounding tissues. According to the "Gate Theory" of pain control (1), as the larger, faster sensory and mechanoreceptive fibers are stimulated, there is less ability for the pain messages from the slower unmyelinated C fibers to reach the gate at the dorsal horn of the spinal cord (Figure 4-B). This results in a reduced perception of pain which decreases the pain-spasm cycle and improves function as indicated in Table 1-B and Figure 3.

Figure 4-A
Red Dots = Pain messages entering dorsal horn of spinal cord.

Figure 4-B
Blue Dots = Proprioception, mechanoreception and touch messages entering dorsal horn.


As demonstrated in Figure 1 and 2, loading injured tissues increases pain, decreases circulation and fortifies the splinting response with increased spasm in surrounding tissues. Moving an injured joint in the water causes a therapeutic decompression effect, which can be enhanced by the addition of a weight distal to the injured joint structure and a flotation device above the injured joint structure. This will encourage further decompression, or light traction, which is known to inhibit and relax the muscles crossing the involved joint (2). The result is often decreased spasm and improved functional muscle contraction. This, too, facilitates venous return, mechanoreceptor stimulation, reduced pain and aids in accelerating recovery (Figure 3).


Phase II signifies the beginning of weightbearing exercise. Phase II may be slowly introduced by having the injured athlete move out of the deep end of the pool and progressively toward the shallow end. This proportionately decreases the clients’ buoyancy. Exercises or movements that stimulate the injured region are continued under progressively increased load, always being careful not to exceed maximum tissue tolerance; the point at which intensity is great enough to induce pain.

Phase II is often enhanced by combining the use of Swiss ball training with pool therapy. Swiss balls provide an excellent means of assessment, correction and progression of an injury and can be an excellent transition between the pool and full body weight exercises against gravity.


Phase III introduces axial loading for injuries of the spine, rib cage and lower extremity. In the upper extremity, Phase III utilizes a progression from an aerobic to anaerobic loading stimulus. Phase III is periodized and progressed in the same manner as a base conditioning program. If progressing your client to work or sport specific exercises, a specificity phase is warranted.

Phase IV is signified by the beginning of the specificity phase and the utilization of power development exercises. Phase IV is also the phase in which elastic energy is enhanced through training via the use of specific plyometric drills.

In Phase II, III and IV, the pool is effectively used as a means of accelerated recovery. As indicated above, the water stimulates the working tissues, causing therapeutic physiological effects that enhance tissue regeneration. Intelligent application of pool therapy can be used to speed recovery and increase both work volume and work tolerance.


The pool provides an excellent opportunity to interrupt the pain-spasm cycle via facilitated venous return, sensory modulation and therapeutic decompression. Intelligent use of the pool for its hydrotherapeutic effects will speed recovery from injury and serve as a means of naturally increasing ones training volume and work tolerance.


  1. Wall PD, Melzack R. Textbook of Pain, 3rd ed. New York: Churchill Livingstone, 1994.
  2. Abreu B.C. Physical Disabilities Manual. New York: Raven Press, 1981.