Therapeutic application of heat. Goal is to increase the temperature of the tissues. Generally used post-acute injury (not during first 48 hours) and for chronic problems.
Effects of heat on tissues:
Vasodilation increased vascular/capillary permeability and blood flow; pain decrease; decreased muscle spasm and tone; decreased joint stiffness; increased local tissue metabolism; increased lymphatic and venous drainage; increased elasticity/extensibility of connective tissues; increased nerve conduction velocity.
Therapeutic benefits of heat are considered to be most efficient when tissues are at a temperature of 41-45 degrees.
Mechanisms of heat transfer to tissues:
1) Conduction (eg hydrocollator pack) – transfer of heat involves the diffusion of energy through collision of molecules. Tissues to be heated need to be in close contact with source. Rate of heat transfer is dependent on the difference in the temperature and the thermal conductivity of the materials.
2) Convection (eg whirlpool) – transfer of heat involves by flow of air or water from the source to the tissues.
3) Radiation (eg infra red lamp) – transfer of heat involves the transfer of energy through space by electromagnetic waves.
4) Energy conversion (eg ultrasound) – heat is generated in the tissues by conversion from another form of energy.
Pain, muscle spasms, soft tissue injuries, contractures, joint stiffness, inflammation.
Open wounds, metal implants, cardiac pacemakers, impaired circulation or sensation, acute inflammation/injury, thrombophlebitis malignancy, poor thermal regulation
Alternating heat and cold
Most protocols use a cold-to-warm ratio of 1:3 to 4 minutes
Little research on effectiveness