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Heat Modalities. Chapter 4 (still). Heat is commonly classified into 3 major categories Chemical action associated with cell metabolism Electrical or magnetic currents as those found in diathermy devices Mechanical action as found with ultrasound

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heat modalities

Heat Modalities

Chapter 4 (still)

Heat is commonly classified into 3 major categories
    • Chemical action associated with cell metabolism
    • Electrical or magnetic currents as those found in diathermy devices
    • Mechanical action as found with ultrasound
  • The application of heat modalities is known as thermotherapy, and methods of heating are classified as being superficial or deep.
Superficial heating agents must be capable of increasing skin temp within a range of 104-113°F.
  • The transfer of heat to underlying tissues occurs via conduction, but superficial heating agents are limited to a depth of less than 2cm.
  • The use of heat is indicated in the subacute and chronic inflammatory stages of injury.
Because the effects of heat application are essentially opposite to those of cold, its use in the treatment of acute injuries should be avoided.
  • Applying heat to an active inflammatory cycle will ↑ the rate of cell metabolism and accelerate the amount of hypoxic injury
classification of heating agents

Infrared lamps

Moist heat packs

Paraffin baths

Warm whirlpools and/or immersion

Deep heat

Microwave diathermy*

Shortwave diathermy


Classification of Heating Agents
local effects of heat application
Local effects of heat application
  • Vasodilation
  • ↑rate of cell metabolism
  • ↑ capillary permeablilty
  • ↑delivery of leukocytes
  • Edema formation
  • Removal of metabolic waste
  • ↑ elasticity of ligaments, capsules, and muscle
  • Analgesia and sedation of nerves
  • ↑nerve conduction
  • ↓muscle tone
  • ↓ muscle spasm
  • Perspiration
some systemic effects of heat exposure
Some systemic effects of Heat exposure*
  • ↑ body temp
  • ↑ pulse rate
  • ↑ respiratory rate
  • ↓ blood pressure
general indications contraindications

Subacute or chronic inflammatory conditions

Reduction of subacute or chronic pain

Subacute or chronic muscle spasm


Hematoma resolution

Reduction of Joint contractures


Acute injuries

Impaired circulation

Poor thermal regulation

Anesthetic areas


Abnormal tissue, such as a tumor, that grows at the expense of healthy tissues

General Indications/Contraindications
effects on the injury response
Effects on the injury response
  • Despite heat and cold produce many of the same outcomes, decreased pain, for example, the timing of when to begin using heat modalities is much more critical
  • If heat is applied too soon in the injury response cycle, the ↑cell metabolism causes an increase in the number of cells injured or destroyed because of hypoxia.
  • ↑ the inflammatory rate may possibly extend the acute and subacute stages
cellular response
Cellular response
  • For each ↑ of 18°F in skin temp, the cells metabolic rate ↑ by a factor of 2-3.
  • As the cell’s metabolic rate ↑, so does its demand for oxygen and nutrients.
  • As with living organisms that consume energy, the amount of waste excreted from the cell ↑ as its activity ↑
  • Also, ↑ metabolic rate ↑ tissue temp.
blood and fluid dynamics
Blood and fluid Dynamics
  • Response of the body to heat is dilating local blood vessels
  • The amount of dilation being greater in superficial vessels than in the deeper vessels
  • ↑ capillary flow results in an ↑ supply of oxygen, nutrients, and antibodies to the effected area
The amount of edema is ↑, but the capability of removing it is greater
  • ↑ capillary pressure forces edema and harmful metabolites from the injured area
  • ↑ permeability aids in the re-absorption of edema and the dissolution of hematomas.
  • These wastes can drain into the venous or lymphatic systems
  • If venous and lymphatic return is not encouraged, further edema occurs.
effects on inflammation
Effects on inflammation
  • Local application of heat accelerates inflammation
  • Soft tissue repair is facilitated through an accelerated metabolic rate and ↑ blood supply
  • Blood flow must be ↑ to encourage the removal of cellular debris and to ↑ delivery of the nutrients necessary for the healing of tissues
↑ oxygen stimulates the breakdown and removal of tissue debris and inflammatory metabolites
  • Nutrients are delivered to the area to fuel the cells, and there is also an ↑ in the delivery of leukocytes, encouraging phagocytosis.
muscle spasm and tissue elasticity
Muscle Spasm and Tissue Elasticity
  • ↑ temperature reduces the primary and secondary muscle spindles’ sensitivity to stretch
    • ↓ the amount of muscle spasm present
  • Increasing blood flow and reducing local muscle metabolites further alleviate spasm
  • Most muscular tissues are not directly heated by superficial heating agents
ROM is subsequently improved by ↑ the extensibility of collagen and the viscosity and plastic deformation of tissues
  • This effect alone is not sufficient to ↓ contractures or ↑ the elasticity of healthy tissues
  • Neither anterior laxity of the knee nor hamstring flexibility has been shown to be affected by heat modalities alone
  • Tension, in the form of gentle stretching, is necessary to elongate muscle and capsular tissues while the tissues are still within the therapeutic range
pain control
Pain Control
  • Mechanical deformation and/or chemical irritation of nerve endings stimulate pain transmission
  • In acute injuries, the primary cause of pain is the mechanical damage done to the tissue in the area.
  • In the subacute and chronic stage of injury, ischemia and irritation cause chemical pain from certain chemical mediators
  • Mechanical pain is caused by increased swelling and the tension placed on the nerves by muscle spasm
Mechanical pain is decreased by reducing the pressure on the nerves , thus lessening the pain-spasm-pain cycle.
    • By encouraging venous and lymphatic return through the use of elevation and muscle contraction, the swelling is removed, decreasing interstitial pressure
  • An increase in temperature leads to a state of analgesia and sedation in the injured area by acting of free nerve endings.
  • Nerve fiber are stimulated, blocking the transmission of pain with a conterirritant effect.
  • This effect appears to last only as long as the stimulus of heat is applied
dissipation of heat
Dissipation of heat
  • When therapeutic heat is applied to the body, there is a rapid rise in skin temperature
  • This rise occurs because energy is being absorbed faster than the cool blood delivered to the area can remove it.
  • After approximately 10-15 minutes of exposure, the temperature gradient begins to even out.
  • At that point, the body is able to counteract the energy being applied by supplying an adequate amount of blood to cool the area
At this time, the patient may claim that the modality has cooled down when, in fact, its intensity is unchanged.
  • When a maximal vasodilation has occurred and the intensity of the treatment stays constant (or increases), the vessels begin to constrict.
  • The phenomenon, known as rebound vasoconstriction, will occur approx 20 min into the treatment.
    • This is the body’s attempt to save underlying tissues by sacrificing the superficial layer.
    • If the intensity of the tx is too great or if the duration is to long, burns will result
  • Mottling of the skin is a warning sign that tissue temp are rising to a dangerously high level.
    • In this case, ghost white areas and beet-red splotches mark the patients skin
    • When this occurs, the tx should be discontinued immediately
heat vs cold
Heat vs Cold
  • How do you know when to use heat and when to use cold??
    • There are no clear cut answers to this question.
    • Many articles have given definitive time frames, such as:
      • Use cold for the first 24 hrs
      • And use heat for the next 48 hrs
    • Unfortunately, statements like these are incorrect and unjustified.
One of this first statements made in this class was that the body heals an injury at its own rate.
  • Not only does this rate vary from person to person but also it may vary from injury to injury in the same person
  • The patients physical and psychological state, as well as the type and amount of tissue damaged, factor into the time frame for required for healing.
The decision-making process is similar to the steps involved when a pipe ruptures in the basement of a house
    • Before bailing out the water and cleaning up the mess, you have to stop the leak.
    • Likewise, before encouraging as increase in the rate of cell metabolism in an injured area, the active process of inflammation must be calmed down first.
Remember cold is indicated under 3 conditions
    • In the acute stages of the inflammation reaction
    • Before ROM exercises
    • After physical activity
  • Heat application is indicated under 5 conditions
    • To control inflammation reaction in its subacute or chronic stages
    • To encourage tissue healing
    • To reduce edema and ecchymosis
    • To improve ROM before physical activity or rehabilitation
    • To promote drainage from an infected site
deciding whether to use heat or cold
Deciding whether to use heat or cold
  • Does the body area feel warm to the touch?
  • Is the injured area still sensitive to light or moderate touch?
  • Does the amount of swelling continue to increase over time?
  • Does swelling increase during activity?
  • Does pain limit the joint’s ROM?
  • Would you consider the acute inflammation process to still be active?
  • Does the patient continue to display improvement with the use of cold modalities?
    • If the answers to these questions are “No” heat can safely be used. As the number of “yes” answers increases, so does the indication for use of cold
paraffin bath
Paraffin Bath
  • A paraffin bath contains a mixture of was and mineral oil in the ratio of 7 parts wax to 1 part oil
  • Melted paraffin is kept at a constant temperature of 118-126°F
  • Temps for tx given to the lower extremity are decreased (113-121°F) because circulation is less efficient
  • Because of its low specific heat paraffin can provide approx 6 times the amount of heat as water
Paraffin is a superficial heating agent used for delivering heat to small, irregular shaped areas
    • Fingers
    • Wrist
    • Hand
    • Foot
  • Although its use in sports medicine is limited, it is an effective method for delivering heat, and this form of application of paraffin is beneficial in chronic conditions in which ROM is not an essential part of the tx protocol
    • Arthritis
    • Chronic inflammatory conditions
effects on the irc
Effects on the IRC
  • In addition to the standard effects of heat, paraffin increases perspiration in the treated area which soften and moisturizes the skin
setup and application
Setup and Application
  • Several methods of application, each with its own advantages and disadvantages
  • Paraffin can act as an insulator is allowed to dry on the skin
  • With this in mind, the amount of heat delivered can be adjusted by increasing or decreasing the wax layers
prep for treatment
Prep for treatment
  • To avoid contamination of the mixture, the body part to be treated should be thoroughly cleaned and dried before treatment.
  • Immersion bath
    • Thoroughly clean skin
    • The patient begins by dipping the body part into the paraffin and removing it. Allow this coat to dry
    • Dip the extremity into the wax 6-12 times to develop the amount of insulation necessary. Allow wax to dry between dips
Instruct the patient to avoid touching the sides and bottom of the heating unit because burns may result
  • Instruct the patient who is receiving an immersion not to move the joints that are in the liquid. The cracking of the wax will allow fresh paraffin to touch the skin, increasing the risk of burns
  • After the treatment, scrape off the hardened paraffin and return it to the unit for reheating, or discard it
pack glove method
Pack (glove) Method
  • The glove method is the safest but least effective way for delivering heat to the body with paraffin wax
  • This method is recommended for those patients who are in the subacute stages of healing or have a vascular or nerve condition that would predispose them to burning
  • The body part may also be elevated during this form of paraffin application
Thoroughly clean the body part
  • Begin treatment by immersing the extremity in the wax so that it becomes completely covered. Remove the body part and allow wax to dry
  • Continue dipping for 7-12 times allowing wax to dry between dips
  • After the final dip, cover the extremity with a plastic bag, aluminum foil, or wax paper. Then wrap and secure a terry cloth towel around the area
  • If indicated, the body part may be elevated.
  • Following the treatment, remove the towel and the inner layering. Scrape off the hardened paraffin and return it to the bath for reheating, or discard it
duration of treatment
Duration of treatment
  • Paraffin treatments are given for 15-20 minutes and may be repeated several times daily
  • The sensation of the paraffin is misleading as to the actual temp of the treatment. The temp of the paraffin is sufficient to cause burns, but its specific heat and thermal capacity requires a longer period of time to transfer the energy
  • Avoid using paraffin with athletes who are required to catch or throw a ball or workers who are required to maintain a good grip after the treatment.
indications contraindications

Subacute or chronic inflammatory conditions

Skin infections

Peripheral nerve injuries before electrical stimulation

Another modality should be considered if the patient lacks temp perception


Acute conditions

Peripheral vascular disease

Areas with sensory loss or scaring


next time
Next time
  • Shortwave diathermy
  • Lab
infrared lamp
Infrared Lamp
  • Provide radiant energy for superficial heating of the skin
  • They are considered radiant modalities because no medium is required to transmit energy
  • 2 types
    • Near infrared (luminous)
    • Far infrared (nonluminous)
  • Treatment energy is produced by passing an electrical current through a carbon or tungsten filament
The intensity of the treatment is controlled by adjusting the current flow through the filament or by changing the distance between the lamp and the tissues
  • Luminous generators produce some degree of visible light
    • Which places them on the “near” end of the infrared spectrum
    • Because visible light is present, some of the treatment energy is reflected by the surface of the skin
  • Nonluminous generators do not produce visible light
    • Placing them on the “far” end of the infrared spectrum
Nonluminous infrared radiation is less penetrating than luminous
    • It has effects at 2mm and at 5-10mm beneath the surface of the skin
  • Because nonluminous infrared is less penetrating, the skin being treated will feel warmer than with luminous
  • Not commonly used in a clinical setting, because of the wide range of heating modalities available
  • However, it was once thought to assist in the healing of open wounds, such as turf burns
    • but it actually deters the healing process because it dehydrates the tissues
effect on the irc
Effect on the IRC
  • Heats the skin almost exclusively
  • Deeper tissues are heated by conduction to depths up to 1 cm.
  • Primary physiological effects occur almost entirely in the superficial skin
  • Hyperemia occurs as a result of increased capillary flow and increased capillary pressure
setup and application42
Setup and application
  • Warm up the lamp if necessary
  • To prevent the concentration of heat, clean the area of any sweat, dirt, or oils, and remove any jewelry
  • Position the patient in a comfortable manner. Drape the body part so that only the area to be treated is exposed
  • If a moist heat treatment is desired, place a damp terry cloth towel over the area
Place the lamp so that the source of heat is approx 24 inches away from the patient. Adjust the lamp so the energy will strike the tissues at a right angle (inverse square law)
  • To prevent burns, instruct the patient not to move
  • Check the patients comfort periodically. The intensity may be adjusted by moving the lamp toward the skin (increasing temp) or away from the skin (decreasing temp)
  • Instruct the patient to summon assistance if the intensity of the treatment becomes too great
duration of treatment44
Duration of treatment
  • 20-30 minutes
  • Given as needed
indications contraindications45
  • Indications
    • Subacute or chronic inflammatory conditions
    • Skin infections
    • Peripheral nerve injuries before electrical stimulation
      • Another modality should be considered if the patient lacks temp perception
  • Contraindications
    • Acute conditions
    • Peripheral vascular disease
    • Areas with sensory loss or scarring
    • sunburns
shortwave diathermy
Shortwave Diathermy
  • A deep-heating modiality
  • Uses energy that is similar to broadcast radio waves but has a shorter wave length
  • The energy is delivered to the body is acutally a high-frequency alternating current, but lacks the properties needed to depolarize motor or sensory nerves.
  • The Federal communication Commission has reserved the frequencies of 13.56, 27.12, and 40.61 for medical use
Structures with high water content, like adipose tissue, blood, and muscle, are selectively heated at depths of 2-5cm.
  • Local tissue temp may reach 107°, but the subcutaneous fat layer dissipates a significant portion of the energy
  • This leads to a secondary heating of the superficial muscle layer by heat conducted from the adipose tissue
  • The amount of intramuscular temp increase compares favorably with that seen during ultrasound application
    • Producing an increase of more than 7 degrees F
Because of the relatively large area affected by diathermy, the deep heating effects are longer lasting than those experienced with ultrasound
  • However, it is less effective on those persons who have a large amount of subcutaneous fat.
  • 2 units that are commonly used
    • The condenser unit
    • The conduction unit
condenser unit
Condenser unit
  • Application by way of a condenser unit places the patient within the actual circuit of the machines unit
  • 2 insulated plates are place on either side of the site being treated
  • The flow of electromagnetic energy passes through the tissues, which act as electrical resistors and produce frictional heating
  • Heating occurs at depths of 2.5-5 cm but is uneven because of differences in the resistance to energy transportation of various tissues
  • When condenser plates or pads are used, heating tends to occur in the subcutaneous tissues and the superficial muscle layer
induction unit
Induction Unit
  • Does not place the patient directly in the units circuit.
  • Tissues are affected by radiation emitted form the electromagnetic field created by the electrode
  • The effects of the induction method may heat tissues up to 5cm beneath the skin
    • But the primary temp increase occurs in the superficial and middle muscle layers
The tissues are place in the electromagnetic field by the use of an insulated cable electrode
  • The cable may be wrapped around the extremity or coiled flat like a pancake and placed on the skin
  • Another method ahs the cable in a self-contained drum
effects on the irc52
Effects on the IRC
  • Heating properties are similar to those of other forms of heat application
    • But tend to occur deeper within the tissues and are based on the treatment intensity
  • During vigorous heating skin temp in the treated area increases 4.3 degrees, and the intra-articular temp of the knee increases 2.5 degrees.
  • Blood flow in the deeper tissues increases, and fibroblastic activity, collagen deposition, and new capillary growth are stimulated.
Muscle spasm is reduced by the sedation of sensory and motor nerves
  • As with all heat applications, there is a local increase in cellular metabolic rate and in perspiration, which must be removed during the treatment
general prep
General prep
  • There must be no metal within the immediate treatment area. The presence of metal will collect and concentrate the energy from the treatment in the same manner that an antenna collects radio waves
  • For personal safety, the clinician should remove any rings, watches, bracelets, and so on
  • Cover the area to be treated with a dry terry cloth towel to absorb perspiration. A portion of the treatment area must remain visible to check for burns during treatment. Avoid any moisture buildup during the treatment because water tends to collect heat. The intensity must be turned to “zero” before drying the area
condenser method
Condenser method
  • Plate setup
    • Adjust the plates so that they are parallel to the skin, 1 inch above the patient. On most units, it is essential that both plates be placed at an equal distance above the tissue. This adjustment can be accomplished by using a spacer, such as a piece of wood. Place the spacer on the patient and lower the plate until the plate and the spacer touch. Remove the spacer and repeat for the other plate. The spacer must be removed before the treatment is started.
Consult the user’s manual for the minimum and maximum distance allowed between the condenser plates.
  • Condenser pad setup
    • Cover the area to be treated with six layers of toweling
    • Place the condenser pads on the toweling. If the pads are used on the same side of the body, place them as far apart as possible. If they are used on the opposite side of the body part (anterior or posterior, medial or lateral), avoid having the patient lie on the pad
    • Secure the pads in place with sandbags or something like that.
induction method
Induction Method
  • Cable setup
    • Place six layers of toweling around the body part
    • Using spacers, wrap the cable around the body part, leaving a minimum of 1” between the coils. The leads to and from the coil should be of equal length
    • Secure the cable ends so that they do not touch each other, the patient, or the shortwave unit itself
Coil setup
    • Using spacers, form a coil of at least three circles approximately equal to the area being treated. There should be a minimum of 1” between the circles, and the leads should be of equal length. Use an insulator or 1” of padding to separate the end of the inner coil from the coil itself
    • Insulate the skin with at least 6 layers of toweling
    • Place the coil on the patient and lightly secure in place with sandbags
    • Position the leads so they do not come in contact with each other, the patient, or the unit.
Drum setup
    • Position the drum approx .5-1” above the toweling. There is a direct relationship between the distance of the drum from the patient and the intensity of energy required for the treatment.
  • Turn the unit on: allow it to warm up if necessary
  • Some units must be turned to allow for maximal energy transfer. If tuning is necessary, consult the user’s manual and follow the manufacturer’s instructions.
  • Instruct the patient not to move until the machine is turned off.
  • Increase the intensity until the athlete feels mild warmth
If the electrodes must be moved or if it becomes necessary to dry the area, return the intensity to zero before making any adjustments
  • Check patient regularly. Observe the skin for signs of burns, and inquire as to any unusual sensations. Adjust as necessary
  • After the treatment, return the intensity dial to “zero” and shut off the unit.
duration of treatment62
Duration of treatment
  • At moderate intensities, treatments may be given for 20-30 minutes and may be repeated as needed for 2 weeks. When higher treatment temps are used, decrease the duration of treatment and apply on alternate days.
  • Many states require a physician’s prescriptions for the application of SWD.
  • Never allow the cables to touch each other. This may create a short circuit
  • The skin exposed to the treatment must always be covered by at least .5” of toweling
  • Do not allow perspiration to collect in the treatment field
Never allow the skin to come into direct contact with the heating unit or cables. Severe burns may result.
  • Excessive amounts of adipose tissue overlying the treatment area can result in overheating the skin
  • Overheating of the patients tissues may cause tissue damage without any immediate signs. Deep-tissue burning can cause destruction of muscular tissue of subcutaneous fat necrosis.
  • A deep, aching sensation may be a symptom of overheating the tissues
It is difficult to heat only localized areas. Water pathways within the tissues dissipate heat formed in the treated area
  • The electromagnetic energy is not localized to the treatment area, radiating 2 to 3 feet from the source of continuous SWD and 2 feet from the source of pulsed diathermy. Clinicians may be placed in the field of this scattering radiation, possibly overexposing them to diathermy. A distance of 3 feet from the source of the energy should be maintained to ensure the operator’s safety.
  • Joint inflammation (bursitis, tendinitis, synovitis) Use with caution as the deep heating may cause collagen destruction within the joint.
  • Large areas, such as the paraspinal muscles, that cannot be effectively heated through other methods because of the size of the target tissues
  • Fibrositis
  • Myositis
  • Subacute and chronic inflammatory conditions in deep-tissue layers
  • osteoarthritis
  • Ischemic areas: the increased metabolic rate increases the need for oxygen, causing further hypoxia
  • Peripheral vascular disease
  • Metal implants or metals such as jewelry. The metal collects and concentrates the energy, potentially causing burns
  • Perspiration and moist dressings. The water collects and concentrates the heat
Tendency to hemorrhage, including menstruation.
  • Cancer
  • Fever
  • Sensory loss
  • Cardiac pacemakers
  • Areas of particular sensitivity
    • Epiphyseal plates in children, the genitals, sites of infection, the abdomen with an implanted intrauterine device (IUD), the eyes and face