1. Metabolic effects
Physiological Effects
of Thermotherapy
2. Vascular effects
3. Neuromuscular effects
4. Connective tissue effects
Metabolic effects
• ↑ 10°C in temperature = ↑ Cell activity and metabolic
rate by 2-3 times. (Van Hoff’s Law)
• ↑ Oxygen uptake by tissues → shifting Oxygen
hemoglobin dissociation curve to the right.
PROMOTE HEALING
Vascular effects
↑ Tissue
temperature
Vasodilatation
Axon reflex
Release of Chemical
mediators
Local Spinal cord
reflexes
Axon Reflex (Direct effect)
Blood vessel
V.D
Thermoreceptors
Heat
Modality
Spinal Cord
Axon Reflex
Heat applied to skin will
stimulate cutaneous
thermoreceptors
Vasodilation
Release of vasoactive
mediators (Nitric oxide)
Thermoreceptors will
carry impulses to the
spinal cord
Some of these afferent
impulses transfer
antidromically toward
skin blood vessels
Release of Chemical mediators (Indirect effect)
Mild
Inflammatory
reaction
Histamine
Vasodilatation
Prostaglandins
Heat
↑ Sweat
secretion
Kallikrein
enzyme is
released
Release
bradykinin
↑ Vascular
permeability
Local Spinal cord reflexes (Indirect effect)
Stimulation of cutaneous thermoreceptors
↓ postganglionic sympathetic nerve
activity to smooth muscles of blood vessels
Vasodilatation
Neuromuscular effect
Effect of heat application on Neural system
1. ↑ Nerve conduction velocity
By 1-2 meters/sec for every ↑ 1°C
2. ↓ Latency of motor and sensory nerve fibers
3. Pain relief + Increased Pain threshold
Activation of cutaneous thermoreceptors has direct inhibitory gating effect on pain impulses
travelling to spinal cord.
4. ↓ Gamma firing rate + ↓ Alpha motor neuron activity
Change in muscle spindle firing rate → Decrease sensitivity of muscle spindle to stretching
Neuromuscular effect
Effect of heat application on Muscular system
1. Relaxation
Increased blood supply to muscle helps to remove lactic acids and metabolic wastes → decrease
pressure on nerve and blood vessels → Muscle relaxation.
2. ↓ Muscle Spasm
Heat application can help break pain-spasm cycle mechanism.
3. Changes in muscle strength
Decrease in the initial 30 minutes after the application due to change in the firing rates of type
II muscle spindle efferent, gamma efferent and type Ib fibers from Golgi tendon organs.
Beyond 30 minutes after the application of heat and for the next 2 hours, muscle strength
gradually recovers and then increase to above pretreatment levels.
Connective tissue effects
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
Thermotherapy temperature benchmarks
50 C
Burn
45 C
44 C
43 C
42 C
41 C
40 C
39 C
38 C
↑
Enzymatic
activity
↑ Release
of O2
(Doubled)
Plastic deformation
of collagen rich
structures
Fluidotherapy
Definition: It is a dry-heat modality
that transfers heat energy by forced
convection.
Components
Fan
Container
Cellulose
particles
Mechanism of Action
1. The
device is
turned on
2. The fan starts to
circulate
3. The cellulose
particles start
to circulate
Air jets circulate heated cellulose particles that have
a lower specific heat and thermal capacity than
water, allowing higher treatment temperatures.
Instrumentation
Advantages vs. Disadvantages
Advantages
Disadvantages
• Easy to use
• Temperature & Speed of application
can be controlled.
• Variety of unit sizes allows for most
body areas to be treated.
• Allows performance of active exercise
during intervention.
• Can be used for desensitization of
hypersensitive hands/fingers or
feet/toes.
• Expensive modality to
purchase.
• Some patients are intolerant
to the enclosed container
(claustrophobic feeling).
• Some patients are intolerant
to the dry materials used.
Video