An underwater treadmill, or hydro-treadmill, can be a valuable addition to any practice. But it is important to understand
its uses and limitations as well as proper operation and maintenance to achieve the greatest benefits.
In this article, we provide an overview of underwater treadmill therapy, including its purpose, common uses for specific conditions,
basic techniques, necessary equipment, and maintenance considerations. We also include a case report as an example of how
the treadmill can be used in the rehabilitation of a patient after anterior cruciate ligament surgery, one of an underwater
treadmill's most common uses. Although the focus of this article is dogs, this modality is also growing in the field of equine
Hydro-treadmill therapy is primarily used in veterinary patients to enable early return to function and improve muscle strength
after limb, neck, or back surgery or injury and improve range of motion in compromised joints. Hydro-treadmill therapy is
also becoming more frequently used in animals for athletic conditioning and weight management.
Orthopedic and neurologic patients can benefit from earlier return to function with underwater treadmill therapy. It provides
a reduced weight-bearing environment that increases functional use of a limb without marked weight loading and resultant discomfort
to a postsurgical joint.1 Patients healing from fractures in which immobilization is necessary often perform well when exercise is first initiated
in water. The water's viscosity also provides increased proprioceptive and tactile stimulation.2
In addition, most postsurgical and neurologic patients have some degree of muscle atrophy or loss of strength. Muscle atrophy
also occurs secondary to osteoarthritis and, to a smaller degree, as a result of normal aging. Walking on an underwater treadmill
once a week or more can help patients with muscle atrophy improve strength and mobility because of the increased resistance
to forward motion. More frequent sessions, as often as every other day, can help build strength even faster.
Many dogs that are unwilling to use a limb after injury will use the limb to help maintain balance and stability in the water
because of increased comfort and because of the resistance to forward motion in the functional limbs, which slows the gait
pattern. Underwater treadmill therapy is particularly useful in small dogs that have undergone femoral head ostectomy. In
these patients, we want healthy pseudo-joint formation rather than excessive scar tissue leading to restricted motion. An
underwater treadmill allows motion in a low-weight-bearing environment to help strengthen the muscles and tendons that surround
this new joint as well as maintain strength and balance in the rest of the body. The reduced weight-bearing stress on the
limb in the initial phases of pseudo-joint formation appears to help to reduce the amount of functional limb length discrepancy
associated with dorsal displacement of the femur in these patients.
Injured joints often show reduced range of motion. Underwater treadmill walking allows a correct but exaggerated gait pattern,
which improves joint flexion, and to a lesser degree, extension.3 The most common example of a patient that would benefit from this exaggerated gait pattern is a patient with limited stifle
and hock flexion after undergoing surgery to repair an anterior cruciate ligament injury (see the related sidebar titled "A case example of physical rehabilitation in a dog after bilateral stifle surgery").
The pain relief provided by warm water facilitates muscle relaxation and tendon stretch in situations in which splinting,
protection, or contracture has occurred.1
Athletes benefit from conditioning on an underwater treadmill both in muscle strengthening and cardiovascular endurance because
of water's increased resistance.
Finally, obese or overweight patients can exercise more safely in a buoyant environment than on land. The water's buoyancy
reduces weight-bearing stress while at the same time its resistance increases metabolic demand and improves muscle strength.1