Physical Agents in Rehabilitation

• Physical agents are forms of energy and materials applied to patients; they include heat, cold, water, pressure, sound, electromagnetic radiation, and electrical currents
• Physical modality and modality are often used interchangeably with the term physical agent

Categories of Physical Agents

• Thermal agents examples include: Diathermy, hot pack, ice pack
• Mechanical agents examples include: Mechanical traction, elastic bandage, whirlpool, ultrasound
• Electromagnetic agents include Ultraviolet and TENS

Thermal Agents

• These transfer energy to a patient, increasing or decreasing tissue temperature through conduction, convection, and radiation
• Superficial thermal agents include hot packs
• Deep heat thermal agents include ultrasound (US), microwave (MW), and shortwave (SW)
• Tissue temperature increase is applied when intending to increase circulation, metabolic rate, soft tissue extensibility, or decrease pain
• Tissue temperature decrease is applied when intending to decrease circulation, metabolic rate, or pain

Mechanical Agents

• These apply mechanical force to increase or decrease pressure on the body
• Traction is used to alleviate pressure on nerves or joints producing pain or sensory changes, normalizing sensation and preventing damage
• Compression counteracts fluid pressure and edema; its force, duration, and application can be varied

Hydrotherapy

• Water is applied via immersion or nonimmersion techniques for therapeutic purposes
• Immersion in water creates pressure which may be used as resistance during exercise, or it may provide buoyancy
• Hydrotherapy transfers heat and can cleanse or debride wounds

Mechanical Wave - Ultrasound

• Ultrasound uses alternating waves to impart mechanical energy for thermal and nonthermal effects in rehabilitation
• Continuous ultrasound at sufficient intensity produces thermal effects, that increase temperature in deep and superficial tissues
• Pulsed ultrasound optimizes mechanical effects to promote tissue healing and facilitate transdermal drug penetration

Electromagnetic Agents

• These apply electromagnetic energy via radiation or electrical current
• Infrared radiation frequencies range from 1011 to 1014 cycles per second, and produces heat only in superficial tissues
• Ultraviolet radiation frequencies range from 7.5 X 1014 to 1015 cycles per second, and it produces erythema and tanning without producing heat
• Continuous shortwave diathermy frequencies range from 10 million to 100 million cycles per second, and it produces heat in both superficial and deep tissues.
• Pulsed shortwave diathermy provides low average intensity of energy and modifies cell membrane permeability for non thermal pain and edema control
• Microwave diathermy and Laser therapy are other types of electromagnetic agents

Electrical Stimulation

• Electrical currents vary in effect and clinical application based on waveform, intensity, duration, direction, and tissue type
• Electrical currents provides sensory or motor stimulation for pain control or muscle strength increase
• Electrical currents can attract or repel charged particles, alter cell membrane permeability to control edema, promote healing, and assist transdermal drug delivery

Role of Physical Agents in Rehabilitation

• In 1995, The American Physical Therapy Association (APTA) stated that the exclusive use of physical agents, requires documentation justifying its use, and should include skilled therapeutic or educational intervention, to be defined as physical therapy

• Physical agents are often used with other interventions

• These interventions include therapeutic exercise, functional training and manual mobilization

• A hot pack can be applied before stretching to increase the extensibility of superficial soft tissues.

Effects of Physical Agents

• Physical agents can modify inflammation and healing
• Physical agents help to relieve pain
• Physical agents can alter collagen extensibility
• Physical agents helps to modify muscle tone

Considerations for Using Physical Agents

• Contraindications are conditions where the treatment would be improper or undesirable
• Precautions are conditions requiring special care or limitations during application

General Contraindications

• Pregnancy creates concern because the agent’s physiological effects could reach and potentially harm the fetus
• Malignancy is a factor as the agent's energy or physiological effects could alter circulation to malignant tissue and accelerate growth or metastasis
• Pacemakers may be altered due to the agent's energy may affect these, dangerously changing a patient’s heart rate
• Impaired sensation and mentation is a factor as the patient may communicate inaccurately

Specific contraindications and precautions differ among the different physical agents