In the field of rehabilitation, hot and cold are both hot. While this may sound a bit cryptic, there is a great deal of truth in this phrase. The fact is that hot and cold therapy are both “hot”—ie, popular—when it comes to treating a variety of injuries and conditions ranging from simple sprains to chronic arthritis. Despite the advances in rehabilitation medicine, they will likely remain that way well into the future. Even with their ever-increasing usage, however, there is some disagreement over which of the two is the more effective for specific physical problems, even among the professionals themselves.

If the goal is to reduce pain and decrease swelling in the affected area immediately following an acute injury, cooling modalities are the more effective approach—certainly within the first 24 to 48 hours after the injury’s occurrence.

After the first 2 days—during the subacute and chronic stages of injury—heat tends to become the modality of choice.1 There is no mystery to how heat works: when applied to an injury, it dilates small blood vessels in the area, subsequently increasing blood flow. This increased blood supply brings with it myriad nutrients and oxygen, which nourish the tissues and hasten healing. Heat offers further benefits, including: decreasing pain; reducing the occurrence of muscle spasm; and relaxing tense tissue, which improves the tissue’s response to stretching.

Heat can be generated through a number of methods, including moist heat therapy, hot-water compresses, whirlpools, infrared lamps, short-wave radiation, high-frequency electrical current, ultrasound, paraffin wax, or warm baths. All heating methods produce basically the same physiological effects; the difference is the depth at which they are produced.2

Moist heat therapy, compresses, and whirlpools are superficial heating modalities, producing heat that penetrates 1 to 5 mm beneath the skin surface. Methods such as these are most effective for stiffness, soreness, or minor musculoskeletal injuries. Deep-heating methods are commonly used for more severe musculoskeletal injuries.1 In fact, these deep-heating modalities, such as ultrasound, elevate tissue temperature much deeper—up to 5 cm beneath the skin surface. Tissues high in protein content, such as nerves, muscles, tendons, ligaments, and joint capsules, absorb ultrasound energy and may be selectively heated.

Also, wet heat penetrates more deeply than dry heat; as such, moist heat is preferred by therapists. What is more, the ease of use, especially in a clinical setting, is attractive: the therapist can simply grab a heat pack, wrap it, and apply it to the affected area.

The length of time that heat is used varies from person to person, but it usually ranges from 10 to 20 minutes. If heat is being applied to patients with limited sensation, the therapist must be extremely cautious, as the patients will be unable to tell if their skin is burning.

A moist heat pack is kept in water that is maintained between 155° and 160°. It is then wrapped in layers of toweling before it is placed on the affected area; some patients like multiple layers, others prefer a single layer. When the ideal level of increased circulation is attained, the skin on the affected area should turn a bright pink. When applied, the temperature of the pack on the skin should be approximately 115° to 118°. Ultimately, it depends on the individual’s tolerance and sensitivity to heat. Individual temperature preference, along with physical makeup and medical status, must be considered with other heating methods as well.

While ultrasound has been shown to be effective for directing heat to a specific body part, opponents question its clinical effectiveness, including the actual depth of penetration, as well as the degree of temperature change. Controversy also exists about whether it can effectively break up scar tissue.3,4 What is more, the need to continuously hold the ultrasound head on the patient can be a major inconvenience to the therapist.

Paraffin is an effective method for delivering heat, particularly for arthritic hands. Another method is diathermy, which uses short-wave, electromagnetic energy to heat tissues deep below the surface of the skin, speeding the healing process. The increased circulation created by the diathermy process supplies the nutrients the body needs to heal the injury, and, coincidentally, increases the range of motion and relaxes muscles, ligaments, and tendons.

As might be expected, ice has the opposite effect of heat. Cold is a vasoconstrictor, causing the blood vessels to narrow and decreasing blood flow. This translates to decreased inflammation and edema following severe injury. It is also believed that cold reduces inflammation by inhibiting histamine and scarring agents, limiting secondary tissue damage.1

Cold also decreases nerve conduction so that the affected area becomes numb, making it an excellent analgesic devoid of side effects. In a rehab regimen, ice is often used after treatment to reduce pain in a mobilized joint and muscle spasm. It also facilitates active or passive joint motion, allowing quicker return to exercise.5

Ice plays an integral role in the “rest, ice, compression, and elevation” (RICE) approach to treatment. Used together immediately after an injury, these four elements can relieve pain, limit swelling, and protect the injured tissue—all of which help speed healing, which occurs as the damaged tissue is replaced by collagen.6 It can ultimately be excellent in treating areas of superficial inflammation.

While there are various ways to apply ice, the traditional ice pack is arguably the most well-established method in rehab facilities. Ice pack solutions are stored at 20° and, like moist heat packs, they are usually wrapped in layers of toweling. Freezing water in paper cups is also popular, as they are convenient to use and allow the therapist to massage a specific body part. This is handy when trying to position the ice on a specific tendon or small joint.

When cold is used to minimize pain and swelling following exercise or a rehabilitation routine, it should be applied for 15 to 30 minutes. If it is applied any longer, the patient risks becoming ischemic.

It is not unusual to employ both modalities in one rehab session: Heat someone up, stretch them out, and ice them down at the end. Some clinicians try to incorporate both heat and cold modalities through the use of contrast baths, which utilize vasoconstriction caused by cold, and vasodilation caused by heat. The result is a “pumping action” that helps remove waste products and excess fluid from the injured area and decreases swelling.7,8

The bottom line? People should not be afraid to combine heat and cold. Heat can promote flexibility before an activity, with ice reducing the secondary effects of the activity. They should realize it is appropriate to combine hot and cold with proper movement and exercise.

What about the person who incurs an injury but does not address it for some time—for example, a basketball player who sprains his ankle but tries to “stick it out” for a few weeks? When a person has had a problem for awhile, they should pay attention to the day-to-day level of discomfort. The rule of thumb should be, if it is still aggravated, put cold on it, whether it is a sprain, pulled muscle, or a number of other acute injuries. Of course, first thing in the morning, heat may feel great, loosening up the affected area for activity. During the day, however, repeated usage of the injured area may generate discomfort. From a tissue standpoint, the affected area does not really “know” that it has suffered an acute injury; rather, it simply feels overworked. That is an appropriate time to switch to ice.

There are other instances in which a person sprained an ankle, iced it early, and rested it. Perhaps they subsequently experienced some swelling from disuse that has been present for some time. The idea now is to pump fluids out of that area to reduce the swelling. Consequently, it would be advisable to put heat on the injured area (ie, warm soaks), followed by cold packs or rubs. The heat will begin the pumping action (increased circulation), which the ice will then shut down. Combined with elevation and movement, this is a very effective treatment approach.

In the end, regardless of how technologically advanced the rehab industry becomes, the use of hot and cold will serve an important function in treating injuries as well as chronic conditions. In other words, these modalities will remain “hot” for years to come.

Bob Reed, MS, PT, is the manager of Braintree Rehabilitation Hospital’s outpatient clinic in Hyannis, Mass.


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