| Should
I heat or should I cool? |
| Without
hesitation this is the most common question we are asked. In
order to answer that question let's review both cold and heat
first. |
| There
are a number of different cold agents available to cool injured
tissues. When cold is applied to the tissues it lowers the
temperature of the skin and the underlying tissue by abstracting
or removing heat from the body. The most common methods of
cooling are placing an ice or cold pack over an area or
immersing in cold water. |
| Cold
packs or ice work on the principle of conduction where the body
part comes in direct contact with the cold agent. Conduction is
the transfer of heat by the direct interaction of the molecules
in the warmer area with those in the cooler area. The magnitude
of the temperature change in the tissue will depend on several
factors including: |
- the
temperature differences between the cold agent and the
tissue;
- the
time of exposure;
- the
thermal conductivity of the area being cooled, for example
muscle verses adipose (fat) tissue
- the
type of cooling agent.
|
| When
cold is applied to an area for 15 minutes or less the immediate
response is vasoconstriction (decreased size) of the blood
vessels in the skin and reduction of blood flow. |
| Cold
is the thermal agent of choice for the first 6 weeks following
injury. During this period the cold will help
to decrease the swelling, inflammation and pain.
Cold also decreases the metabolic rate and this is important
because it will help to lessen the secondary injuries to the
area from a lack of oxygen. Cold has also been found to decrease
the nerve conduction speed. Transmission of impulses, for
example impulses caused by painful stimuli, have been found to
be decreased or even blocked. |
|
A
commercial ice pack or ice cubes work effectively to cool
underlying tissues. The cold source should be placed in
a wet towel and left on the skin for 10 to 15 minutes.
It is important that the ice pack is not left on the skin for
longer than 15 minutes.
The
physiological effects of ice are reversed after 15 minutes of
treatment. The benefits of ice occur because of the
vasoconstriction of the blood vessels. After 15 minutes of cold
application the blood vessels will dilate rather than constrict.
Dilation of the blood vessels will cause the inflammation to
worsen. This response to cold is called the Hunting’s
response. The ice pack can be applied as often as necessary
throughout the day, however there should be 30 minutes between
applications to prevent Hunting’s response from occurring.
After the ice pack has been applied for 5 minutes the skin
should be checked for excessive redness, or discomfort. If these
symptoms are present the ice pack should be removed. |
| Cold
treatment should not be used by people with cold sensitivity
symptoms. Cold therapy is also contraindicated over areas of
poor circulation. Patients with diabetes or peripheral vascular
disease have decreased circulation to their extremities to
varying degrees depending on the severity of the disease. When
cold is placed over an area the local blood flow decreases. It
would not be safe to further decrease the blood flow in the
extremity that already has compromised circulation. |
| There
are many thermal agents available for tissue heating. These
generally fall within one of two categories: superficial and
deep heating agents. Superficial agents include hot packs,
paraffin wax, and a warm whirlpool. Deep heating agents such as
ultrasound are used to increase the temperature of deeper
tissues. |
| Many
physiological changes occur with the application of both
superficial and deep heat to the body tissues. The magnitude of
these changes depends on several factors: |
- the
extent of the temperature rise;
-
the rate of temperature increase within the tissue
- the
amount of tissue exposed to the heat.
|
| In
order to achieve the maximal therapeutic effect of the heat the
tissue temperature should be increased to between 40° C and 45°
C (104° F and 113° F). Once the tissues reach this temperature
the blood
flow will increase to the heated area.
Tissues heated to temperatures above this level have the
potential to burn. |
|
Elevating
the tissue temperature has many therapeutic advantages. Chemical
reactions in the cells within the body are influenced by
temperature. An increase in the chemical reaction allows for an
increase in oxygen uptake, therefore more nutrients will be
available to help the tissues heal more quickly. Heating an area
is also associated with an increased blood flow to the area.
With increased blood in the injured area, nutrients are
delivered and wastes are carried away from the area more
effectively.
Therapeutic
heating has also shown
to decrease pain and to help reduce muscle spasms.
The physiological changes underlying these benefits include; an
elevation of the level where pain is felt, a change in the speed
of signal conduction along a nerve and a decrease in the rate of
activation of the muscle fibers.
Temperature
elevation in combination with a stretch will also help to alter
the length of connective tissue. Following an injury connective
tissue structures will progressively shorten if full range of
motion exercises are not performed. Adhesions may develop
between the tissue layers and scar tissue may form at the site
of injury to further limit mobility. Heat and stretch in
combination can result in decreased joint stiffness and
increased tissue flexibility, thus facilitating ease of movement
and gains in range of motion. |
| There
are two kinds of superficial heat: Moist
& Dry.
Moist heat penetrates the skin and reaches the muscles,
ligaments and joints. Dry heat does not go past the skin.
Examples of dry heat are electric pads, hot water bottles, etc.
Moist heat requires moistness or dampness. It is the moistness
that penetrates. The most efficient way to use heat at home is
to wrap a damp towel around the source of heat (except
electrical) and then a dry towel. Apply to the area for 15 to 20
minutes maximum. |
| The
following conditions indicate it is not safe to use heat as a
treatment option: |
- Inability
to distinguish between hot & cold sensation in the area
of heat application.
- Inadequate
circulation in the area of heat application.
- Recent
or potential hemorrhage in the treatment area.
- Cancer
in the treatment area.
- Acute
inflammation of the treatment area.
- Local
infection.
- Presence
of liniments or heat oils on the skin.
|
| Based
on the above discussion, we use the following simple rules: |
- If
there is swelling and pain use ice.
- If
there is no swelling, but stiffness is present use heat.
- If
this is an acute injury (within first 6 weeks) use ice.
- When
in doubt…use ice.
|
|
