Local and Systemic Effects

The local and systemic effects of cold modalities and the injury response cycle:

1. Inflammation - since there is a decrease in cell metabolism and therefore cell waste,there is a decrease in prostaglandins. Since the rate of prostaglandins slowed down, there is a decrease in edema and pain.
2. Edema reduction/control - Since there is a decrease in blood flow and capillary permeability, the cold modalities can provide the optimal healing environment for acute injuries. This is because there is a decrease in capillary permeability, leading to improved oxygen and nutrient delivery.
3. Muscle spasm - When there is a nine-degree change in skin temperature, there is a decrease in sensitivity of muscle spindle activity and this therefore leads to a decrease in pain. In addition, there is a decrease in afferent output and nerve conduction velocity. This shuts down the feedback loop and lowers sensitivity to movement.
4. Pain - With the application of cold modalities, the patient feels the following sensations: cold, a burning sensation, then aching, and finally numbness sets in. The numbing sensation allows for the analgesic effect of the modality. Also, because there is a decrease in nerve conduction velocity there is a decrease in pain. Cold and hot modalities both rely on the gate control theory to block out pain and try to stop the pain-spasm-pain cycle.

The local and systemic effects of heat modalities and the injury response cycle:

1. Inflammation/edema - Heat speeds up the inflammation rate because there is an increase in blood flow and metabolic rate. Phagocytosis is initiated by an increase in leukocytes in the area.
2. Muscle spasm - The muscle spindles are less sensitive to stretching when there is an increase in temperature. When the muscle spindles are less sensitive, this then decreases the spasm present. Also, heat increases ROM by increasing the collagen extensibility.
3. Pain control - The increased circulation caused by heating modalities helps lessen the pain because the "pain-producing" chemicals in the area are in less concentration. Heat also causes a feeling of sedation and a state of analgesia. This feeling is present when the heat is on and dissipates when the heat is taken away.

Physiological effects of cryotherapy

• Local effects include:
  1. Decrease in pain
  2. Vasoconstriction
  3. Decrease in muscle spasm
  4. Reduction in inflammation
  5. Decrease in rate of cell metabolism
     • Decrease in the need of oxygen
     • Decrease in cell waste

• Systemic effects include:
  1. General vasoconstriction
  2. Decrease in heart rate and respiration
  3. Shivering and increase in muscle tone

* To have systemic effects, there needs to be a .2 degree Fahrenheit change in the core body temperature.

Physiological effects of thermotherapy

• Local effects include:
  1. Vasodilation
  2. Decreased muscle tone and spasm
  3. Increased elasticity of ligaments, capsules and muscles
  4. Analgesia and sedation of nerves
  5. Edema formation
  6. Increased rate of cell metabolism
  7. Increased capillary permeability

• Systemic effects include:
  1. Increased body temp
  2. Increased pulse rate
  3. Increased respiratory rate
  4. Decreased blood pressure

* The use of heat is often used in the subacute and chronic stages