210 Canine Sports Medicine and Rehabilitation
abduction and rotation. The underwater tread-
mill is preferable to swimming during early
rehabilitation for patients that have had total
hip replacement as swimming can cause excess
strain on the soft tissues of the coxofemoral
joint. Dogs with muscle/tendon injuries should
avoid swimming as this can cause excessive
strain on healing soft tissues. Patients with
wobblers or cervical disc disease should not
swim as they tend to extend their cervical spine
excessively. UWTM therapy is an option for
this group. Toy breed puppies and seniors
should be kept warm throughout the session.
During cold weather clients are asked to start
and warm their car when the dog comes out of
the pool so that by the time the patient is dry,
the car is warm.
Physical properties of water relevant
to canine sports medicine
The inherent properties of water make aquatic
training efficient for achieving rehabilitation
and maintaining total fitness (Bishop et al., 1989;
Thein & McNamara, 1992).
Buoyancy
Archimedes’ principle states that when a body
is wholly or partially immersed in a fluid, it
experiences an upward thrust equal to the
weight of the displaced fluid. As water depth
increases, weight bearing decreases, thus
reducing the compressive forces on joints
(Bates & Hanson, 1992).
Hydrostatic pressure
Pascal’s law states that fluid pressure is exerted
equally on all surfaces of an immersed body at
rest at a given depth; this pressure increases
with the density of the fluid and depth of sub-
mersion. Hydrostatic pressure reduces limb
edema and pooling of fluid and blood in super-
ficial and deep tissues thereby encouraging
healing and reducing complication rates.
Hydrostatic pressure causes a decrease in nocic-
eptor sensitivity resulting in pain reduction
(Bates & Hanson, 1992; Ruoti et al., 1997).
The hydrostatic effects on the cardiopulmo-
nary system result in a central shift of the
peripheral blood volume (Arborelius et al.,
1972). This results in increased diuresis so
patients may urinate large quantities shortly
after swimming. Due to hydrostatic pressure,
dogs with chest expansion problems related to
congestive heart failure or pulmonary disease
need careful monitoring. The hydrostatic
pressure properties of aquatic therapy can be
used to strengthen intercostal muscles as a
mild resistance exercise.ViscosityViscosity is the frictional resistance created by
the cohesiveness of fluid molecules. Water is
15 times more viscous than air thus requiring
more effort to move through it. Water walking
for humans, with the water at shoulder height,
requires 65% more effort than walking on land
(Greene et al., 2009). Working against viscosity
increases muscle strength, tone, and cardiac fit-
ness (Ruoti et al., 1997). Viscosity helps weak
canine patients to stand and walk before they
can do so on land.Fluid dynamicsHydrodynamic forces impact any object in
water. These forces include laminal flow, fron-
tal resistance, and drag. Laminal and turbulent
flow affect effort. Laminal flow is the straight
flow of water particles moving at one speed
and in one direction. Resistance to movement
increases with the velocity of flow. Turbulent
flow is the interrupted flow of water particles in
all directions, creating more dramatic pressure
differentials. Here, resistance increases expo-
nentially with velocity. These fluid dynamic
principles have clinical application when
designing swimming or UWTM programs
(Ruoti et al., 1997).
While swimming, friction and turbulence
are the dominant resistive factors (Hall et al.,
1990; Ruoti et al., 1997). Faster swimming or
water walking creates greater turbulence,
resistance, and friction and therefore increases
exertion (Figure 9.1). This is advantageous
for patients needing an intense workout but