Healing Waters


Treating osteoarthritis with aquatic therapy.

By Dennis Dolny, PhD, and Eadric Bressel, PhD

Osteoarthritis (OA) is the most common form of arthritis and affects approximately 27 million Americans.1 Because of the associated joint pain and decreased range of motion, it is a challenge for those suffering from OA to maintain a physically active lifestyle. Frequent movement is a hard sell to someone in pain. Yet, the key to controlling this debilitating disease is to move consistently, which will ultimately reduce pain and increase mobility.

Joint pain and decreased range of motion, the two major roadblocks to exercise for the OA patient, can be alleviated through aquatic therapy. Therapy with an underwater treadmill and therapeutic resistance jets can be the gateway to physical activity and a more fulfilling life for the OA patient.


While patients move through the water, the body weight supportive force of buoyancy significantly decreases the magnitude of the vertical ground reaction force (force applied by ground directed up through the joints of the leg), compared to land-based exercise. For patients who normally experience significant joint pain on land, water treadmill exercise decreases pain. Patients find it easy to move freely and tolerate more intense exercise with minimal residual soreness because of water’s buoyancy de-weighting the patient’s body mass. Adjusting water levels creates the ideal environment for patients to work through a program at various support levels while maintaining proper walking mechanics and posture.

Drag Forces

Compared to air, water is about 800 times denser; therefore, greater resistance is met to a person moving arms and legs through water versus air. The magnitude of resistance (drag force) requires more effort, especially when limbs are moved rapidly. This drag force acts in concert with buoyancy so more effort is required to move limbs through the water, yet limb joints experience less stress.


High Intensity Interval Training

High intensity aerobic interval training is a very popular method to improve performance in athletes and recreationally active healthy individuals. Now this method is available for OA patients utilizing a water treadmill. In addition, adding resistance jets to walking at a moderate pace (2–3 mph) nearly doubles energy expenditure without stressing the leg joints by walking faster. Aerobic interval training utilizing short walking bouts of one to three minutes separated by one to three minutes of recovery—including bouts which patients approach 90 to 95 percent of effort—is actually more effective in improving balance and postural improvement than a moderate 20-30 minute walk. OA patients find it difficult to increase exercise intensity on their own. The therapist’s ability to gradually increase belt speed on the underwater treadmill or the velocity of resistance jets during treatment is a significant advantage.

Patient Confidence

Patients find it refreshing to not only walk freely again in the water, but also exercise at high intensities, which breeds confidence. Many patients who have not attempted high intensity training in many years feel an increased sense of accomplishment and confidence when doing so, resulting in functional improvements and a greater sense of well-being.

Results Transfer Immediately to Land ADLs

Patients may feel great while exercising in water, but how well does aquatic exercise transfer back to land? A 2010 study demonstrates that aquatic training improves balance in OA patients on land, immediately. Patients’ activities of daily living (ADLs) improve, as demonstrated in Timed Up and Go test and climbing and descending stairs. Patients report less joint pain immediately following an aquatic exercise session, as well as throughout the day. Knee range of motion increases after aquatic-based exercise.

Dennis Dolny, PhD, is a department head and professor at Utah State University and a consultant with Hydroworx. He can be reached at dennis.dolny@usu.edu.

Eadric Bressel, PhD, is a professor and research scientist at the Worley Sports Medicine Center at Utah State University and a consultant with Hydroworx. He can be reached at eadric.bressel@usu.edu.


1. Arthritis rheum. [Data Source: NHANES] www.cdc.gov/arthritis/data_statistics/arthritis_related_stats.htm. 2008: 58(1): 26-35. Accessed March 2014.

2. Denning WM, Bressel E, Dolny DG. Underwater treadmill exercise as a potential treatment for adults with osteoarthritis. International Journal of Aquatic Research and Education. February 2010.

Clinical Study

The following February 2010 clinical study from Utah State University, “Underwater Treadmill Exercise as a Potential Treatment for Adults with Osteoarthritis,” published in the International Journal of Aquatic Research and Education2 demonstrates the effectiveness of an underwater exercise program for those suffering from joint discomfort while exercising.

Purpose: The study examined the levels of perceived pain and mobility in osteoarthritis patients after using underwater and land treadmills.

Method: Nineteen patients, diagnosed with osteoarthritis in the knee, hip, and ankle participated in the study. Each participant performed three consecutive exercise sessions on an underwater treadmill and a land treadmill, separating exercise periods by 24 hours and exercise mode by one week.

Results: Results of this study indicated that patients diagnosed with OA may walk on an underwater treadmill at a moderate intensity with less pain and equivalent energy expenditures, compared with walking on a land-based treadmill at a similar moderate intensity. Patients revealed that pain was 140 percent greater during land treadmill exercise sessions than during underwater treadmill exercise sessions.

Conclusion: Patients diagnosed with OA may receive the same aerobic conditioning with less joint pain and greater improvements in mobility by utilizing underwater treadmills opposed to land treadmills.

Underwater Treadmill Running—The Low Impact, Pain-Free Calorie-Burning Fitness Advantage, Alberto Salazar and Dr. Dennis Dolny, 2012. The Use of Aquatics in Orthopedic and Sports Medicine Rehabilitation and Physical Conditioning, Kevin E. Wilk, David M. Joyner.

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