Temperature Therapy:
Works primarily by increasing vasodilation and vasopermeability; can also affect the โpain gateโ
Heat: Directly stimulates Aฮฒ sensory nerves, having some effect on the โpain gateโ, mimicking the neural stimulation modalities. Heat also increases the metabolic rate of the tissue, increasing cellular activity, and mimicking the cellular excitation modalities. Furthermore, warming a tissue up, directly leads to increased vasodilation, and vasopermeability, acting as a catalyst for the healing process (at all stages). Heat can also directly increase extensibility of tissue, resulting in relief from muscle spasm, and increased range of motion. Heat will exacerbate any bleeding &/ oedema locally.
Cold: Cold, applied for up to 5 minutes, produces vasoconstriction, which will help to reduce bleeding and oedema in the early stages of the healing process. If applied for more than 5 minutes (but less than 15 minutes), cold produces vasodilation and vasopermeability, which assist the healing process at all stages; however, it will dampen down the activity level of the cells in the area, and thus slow the healing process.
If used little and often (approximately every 10 minutes, applied once every 90 minutes or so), the cold will create vasodilation and vasopermeability, allowing more blood into the area affected; but then, by removing the ice, the bodyโs own thermoregulation will immediately warm the area, exciting the cells, who can then use the extra blood supply provided by the ice. These vascular effects last longer after ice than they do after heat therapies. If overused (more than 15 minutes, or more frequently than every 60 minutes or so) then the use of cold therapy will slow down the healing process. Ice also has an analgesic effect through stimulation of the Aฮฒ and Aฮด sensory nerves, combined with the reduced conductivity of the C (nociceptive) sensory fibres (stimulating the A fibres out-competes the reduced conductivity).
As a rule of thumb, use heat for a muscluar problem, use ice for a jointy problem, or during the acute phase.