1. Physiological Properties of Thermal Modalities (2)

2. Physiological Effects of Heat
1. Haemodynamic Effects:
Vasodilation
Increases the rate of blood flow (locally and systemically)
It is increases more locally

3. 1. Haemodynamic Effects:
It occurs due to:
Direct activation  on the smooth muscles of blood vessels
Indirect activation
Effect on spinal cord on the grey matter  smooth muscle
Sympathetic nervous system  vasodilation

4. 1. Haemodynamic Effects:
No increase in the temperature of most muscles
Protect body from excessive damage
Convection reduce the risk of burning

5. 2. Neuromuscular Effects:
Change in nerve conduction velocity and firing rate:
Change in nerve conduction velocity (N.V.C)
Decrease conduction latency (in sensory & motor nerves)
Increase pain threshold
Direct  gating
Indirect   ischemia +  muscle spasm

6. 3. Metabolic Effects: Increase metabolic rate
Increase the rate of chemical reactions including enzymatic activity
Up to 45°C
Increase rate of cellular biochemical reactions
Increase O2 uptake
Increase healing

7. 4. Alter Tissue Extensibility :
Increase collagen extensibility
Stretching the soft tissue without heating  elastic deformation
Stretching the soft tissue with heating  plastic deformation
Plastic deformation is due to the change in the viscoelasticity of collagen fibers + the organization of collagen fibers
°C from 5 – 10 minutes (when applying the agent apply for 15 minutes)

8. Physiological Effects of Heat
Factors affecting these physiological effects:
Size of the heated area
Depth of absorption of specific radiation
Duration of heating
Frequency of treatment
Intensity of radiation
Method of application

9. Therapeutic Effects of Heat
Pain control:
Direct due to gating
Indirect through healing,  muscle spasm,  ischemia
 Skin temperature
Not recommended for acute inflammation.
Remember! Applying hot agents to acute inflammation might cause destruction of the tissue

10. Therapeutic Effects of Heat
Increase range of motion and decrease joint stiffness
 Soft tissue extensibility
Passive stretch (45°C for 5-10 minutes)
 Extensibility and viscoelasticity of particular structures (joint capsule, ligaments ..etc)
Superficial stretching (hot pack, infrared, paraffin)
Deep stretching (ultrasound, shortwave diathermy)

11. Therapeutic Effects of Heat
Accelerate healing
 Circulation
 Enzymatic activity
O2, nutrients, remove waste products
In chronic inflammation (third & forth stages of inflammation)
Inflammation & healing rapidly

12. Therapeutic Effects of Heat
Reduction of muscle spasm
Golgi tendon
Muscle spindle

13. Prophylaxis of pressure sores
Sedative effect
Sleeping
Prophylaxis of pressure sores
 Blood flow
Risk of skin breakdown
Skin disease
Like I.R.
Precursor for other treatment (Before stretching, exercises ,massage)

14. Contraindications of Superficial Heating
Acute injury or inflammation
Recent or potential hemorrhage
Thrombophlibitis
Impaired sensation
Impaired mentatiion
Malignancy
I.R irradiation to eyes damage of retina (use a goggle)

15. Precautions Pregnancy Impaired circulation Poor thermal regulation
Edema chronic  hot agent + elevation
Cardiac insufficiency
Metal in the area
Over an open wound
Over area where topical counterirritant hae recently been applied

16. Adverse Effects of Thermo-therapy
Burns
 Intensity
Too long time of application
Patient fall asleep
Contraindicating
Fainting
Vasodilation   blood flow in the area treated   blood pressure

17. Adverse Effects of Thermo-therapy
Bleeding
Skin and eye damage from I.R irradiation

18. Conductive Agents Heat Methods of Application
Two types of heat:
Dry heat: increase surface temperature
Wet heat: increase temperature slightly deeper
Conduct techniques:
Superficial
Deep

19. Conductive Agents Heat Methods of Application
Superficial contact heat depends on:
Intensity of heat
Length of exposure to heat
Thermal medium for surface heat

20. Conductive Agents Heat Methods of Application
Heating tempreture 40 – 45°C
Above this level  burning
Below this level  mild effect
Maximum elevation of skin temperature within 6-8 minutes
Deep contact  deep heat modalities

21.  Good Luck 