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Aquatic Physical Therapy Principles

An aquatic exercise is a form of outcome-based movement that has been utilized for many years. There are several types of aquatic exercises that vary based on the goal and the format.  The major difference between aquatic exercise and land-based exercise is the buoyant support in the water.  Buoyancy has a therapeutic effect of decreasing stress on weight-bearing joints.  Injury and pain risk in aquatic exercise is greatly minimized due to this support and decreased joint stress.  Our doctors of physical therapy can apply a more optimal load through utilizing aquatic physical therapy and bridge to land-based therapeutic exercises and modalities.

Aquatic Exercise vs Skilled Therapy

Aquatic exercise and aquatic physical therapy are not the same things.  When specifically speaking of aquatic exercise, the goals may be to work on fitness, strength, weight loss, muscular endurance, or muscular strength and the individual does not require the supervision and direction of the therapist.   In contrast, Aquatic therapy is designed to treat a specific deficit or dysfunction in the body that limits normal functioning of the body.  In addition, aquatic therapy is designed and individually tailored to meet the needs of a specific patient by a doctor of physical therapy.  The following are guidelines on when an individual may be a good candidate for skilled aquatic physical therapy versus aquatic exercise alone.

Aquatic physical therapy requires the “skilled service” of a PT and/or PTA which may include:

a) the clinical reasoning and decision-making skills of a PT/PTA;

b) the patient has impairments and/or disabilities that can be minimized or eliminated with aquatic physical therapy; and

c) the patient has the potential for reaching new functional goals/outcomes to improve quality of life and ease the burden of care.

Common Benefits and Laws of Aquatic therapy

A study performed in 1997 by Kravitz showed that both blood pressure and resting pulse rates were decreased with aquatic therapy twice a week for 4 weeks as a short – term outcome. These results indicate that an individual can have substantially improved cardiovascular outcomes through aquatic therapy.   In a related study done by Lindle, aquatic walking had a 110% greater energy cost than treadmill walking.  These results demonstrate that though the aquatic environment may be less stressful on the joints, the overall cardiovascular results are similar to land-based exercises.

There are many benefits of aquatic therapy in addition to the low-stress environment introduced by buoyancy.  Some of those perks include improved ability to perform a range of motion and flexibility exercises for those where land-based exercises are too much load, safe environment for working on balance, edema/swelling control, improved muscle tone and strength, improved cardiovascular endurance, and increased sensory output.   Buoyancy will aid in passive range of motion and flexibility with decreased muscle guarding.  The hydrostatic pressure of the water increases sensory output with all motion and exercises performed, as well as assisting with edema control.  The drag, or resistance in the water aids in improving muscle tone and strength.  All of these different factors can make water a safe alternative, as well as an adjunct to land-based therapy.


This increases resistance by adding more travel through the water, thus more effort is required


The reaction of a body as measured by its acceleration is proportional to the force applied and inversely proportional to its mass.  In plain English,, if you use muscular effort, you accelerate or increase the force.  So the greater the body mass, the more force it takes to move that mass.


Newton discovered that for every action of movement, there is applied an equal and opposite reaction.  The viscosity of the water with arms and legs can be used to either “assist” or “impede” movement.  An example might be jogging forward with front arm crawls o assist, which would be less load then jogging forward pushing arms forward (impeding movement more).


Viscosity is defined as the friction between molecules of liquid that causes them to adhere to each other or a submerged body.  So in aquatic therapy, the larger the surface area the more resistance applied.  The smaller the surface area, the less resistance you will receive to movement.  Our doctors of physical therapy have tools and devices that allow us to manipulate resistance for optimal outcome, thanks to viscosity.


Most movements performed in the water get rid of negative contractions (or eccentric contractions).  While this is detrimental for a long term rehab program, it is very useful for starting movement-based programs because it eliminates 95% of soreness that comes from eccentric contractions.  Our recommendation is to start with aquatic therapy (for individuals where the soreness is limiting progress) and advance to concentric and eccentric based therapeutic exercises (get back to land).


Water assists in widening the base of support which stabilizes the center of gravity.  It provides a safer environment for balance retraining.


This law refers to the center of the volume of the body displacing water.  Because of this phenomenon, buoyancy decreases the effects of gravity and reduces the compression of joints.  In water up to the neck, one will see a 90% reduction in compression.  Water to the waist will reduce compression up to 50%.  Joint capsules open when submerged creating greater flexibility for ROM needs.


Pressure increases with depth and has substantial effects on the body.  We see an increased blood flow from 1.8 to 4.1 mL/min/100g of tissue resulting in increased oxygen delivery and circulatory force.  We also experience improvement with dependent edema causing reduced swelling.  Renal blood flow is increased by 10% causing increased urinary output and waste excretion.

Bridge from Water to Land

Because we do not live in the water, a comprehensive aquatic rehab program should incorporate transitions to land-based therapy as appropriate and meeting optimal load requirements.  WPT programs bridge the patient from water to land as appropriate and regress back to water when required for the patient to progress in rehab goals.

Good Candidates for Aquatic Physical Therapy

Aquatic therapy is NOT for everyone.  Those with an extreme fear of water are expected to have greater outcomes with alternative therapies.  Also, individuals with any infections, open wounds, influenza, urinary tract infections, vomiting, or incontinence should not participate in aquatic therapy.

There are many people that may benefit from aquatic therapy or a combination of land/aquatic therapy.  Some of these individuals include those with arthritis, after a back injury/surgery, those with chronic pain, fibromyalgia, spinal cord injury, joint replacement, sports injuries, chronic swelling, obesity, knee injury, post-surgery such as ACL or RTC, or stroke.  The aforementioned list is not exhaustive but provides a sample of the types of individuals that may respond very well to aquatic therapy.

Wright Physical Therapy offers comprehensive aquatic and land-based programs for orthopedic and sports-related injuries.  Click here for more information about our aquatic programs, to find a Wright Physical Therapy location near me.