This notes include some points on the effect of heat on human body

1. THERMOTHERAPY
Rahul.A.P
Asst Proff:LIAHS
BPT,MPT,MIAP

2.  Specific heat is a physical property of matter.
 All matter has a temperature associated with it.
 The temperature of matter is a direct measure of
the motion of the molecules.
 The greater the motion the higher the
temperature.

3.  Motion requires an energy, Typically this
energy is supplied by heat.
 The more energy matter has the higher
temperature
 Temperature loss or gain by matter is
equivalent to energy loss or gain.

4.  Specific heat - is the amount of energy required
to raise the temperature of 1g of substance to
1ºC, and is generally expressed in joules per
gram degree Celsius ( J/g ºC )
 The specific heat of different materials and body
tissues differs
 For example skin has higher specific heat (3.77
J/g ºC) than fat or bone and water has higher
specific heat (4.19 J/g ºC ) than air

5.  Materials with high specific heat requires more
energy to heat up and hold more energy than
materials with low specific heat when both are
at the same temperature.
 Therefore, to transfer the same amount of heat
to a patient , thermal agents with a high
specific heat, such as water are applied than
air based thermal agents

6.  Heat energy transfer from a point of higher
concentration to a point of lower
concentration
 Heat can be transferred to a body or from a
body by conduction, convection, conversion,
radiation and evaporation.

7.  Heating by conduction is the result of energy
exchange by direct collision between the
molecules (molecular agitation) of two
materials at different temperature through
physical contact.
 The faster moving molecules in the warmer
material collide with molecules in the cooler
material and cause them to accelerate
 Heat transfer continuous until the temperature
and speed of molecular movement of both
material become equal

9.  If the physical agent used is cooler than the
patient’s skin (ice pack) heat will be
transferred from patient to the agent and the
temperature of the superficial tissue in contact
with the cooling agent will fall.
 Heat can also be transferred from one area of
the body to another, when one area is get
heated the adjacent tissue and the tissue in
contact with that will increase in temperature
by conduction.

10.  Here the heat transfer occurs by the result of
direct contact between a circulating medium
(fluid or air) and another material of a different
temperature.
 Here the transmission occurs by the physical
movements of the molecules over the cooler
body parts eg- whirl pool, hydrotherapy and
saline bath.

12.  Here new parts of the heating agent at the initial
treatment temperature keeps coming in to
contact with the patient’s body part
 While comparing with conduction here in
convection it transfers more heat in the same
period of time for same material at same initial
temperature
 For eg: heating a body part with whirlpool will
heat more rapidly than immersing in a bowl of
water with the same temperature.
 The faster the water moves , more rapid the
heat transfer.

13.  Here the heat is produced from the conversion
of a non thermal form of energy such as
mechanical or electrical in to heat.
 Ultrasound – which is a mechanical form of
energy, is converted in to heat when applied to
a tissue.
 The ultrasound waves causes vibration of the
molecules in the tissues, thereby generating
friction between molecules resulting in an
increased tissue temperature

15.  Short wave Diathermy –which is a
electromagnetic form of energy, when applied
to the body causes rotation of molecules and
result in friction between molecules which
produce increased tissue temperature.
 Here in conversion the rate of heat transfer is
depends up on the power of the energy source.
 Heat transfer by conversion does not need any
direct contact between the thermal agent and
the body.
 A gel, lotion or water can be used eg-(UST)
other wise air comes in between and transmit
US poorly.

17.  Heating by radiation involves the direct transfer of
energy from a material with higher temperature to a
material with lower temperature by electromagnetic
radiation with out any intervening medium or
contact, (IRR,UVR etc..)
 The rate of temperature increases depends on the
intensity of the radiation, size of the are been
treated, distance of source from the treatment area
and the angle of the tissue kept.

19.  For evaporation a material should absorb an
energy and thus change its form from a liquid
to gas or vapor.
 In human body the heat is absorbed by the
liquid on the skin surface and cools the skin
as it turns in to a gaseous state.
 Eg- when a vapocoolant spray is heated by
the warm skin it change from its liquid form
to a vapor state, during this process the spray
absorbs heat and leaves the skin to cool.

20. Thermotherapy
What is thermotherapy?
 The therapeutic application of heat is called
thermotherapy
 It is used primarily to control pain, increase
circulation, increase soft tissue extensibility and
accelerate healing in rehabilitation side
 The heat has some role in hemodynamic,
neuromuscular and metabolic processes

21. superficial
Heat modalities
deep

22.  SUPERFICIAL HEATING
MODALITIES
1) WAX THERAPY
2) MOIST HEAT
3) CONTRAST BATH
4) FLUIDOTHERAPY
5) WHIRL POOL BATH
 DEEP HEATING
MODALITIES
1) SWD
2) MWD
3) UST
4) IRR
5) UVR
6) LASER

23. Vasodilatation or increased blood supply
 Heat causes vasodialation in the local cutaneous
blood vessels and results in an increased blood flow
to the area.
 Thermotherapy can cause vasodilatation in many
ways.
 Local release of chemical mediators of inflammation
 Indirect activation of local spinal cord reflex by
cutaneous thermo receptors
 Direct reflex activation of smooth muscle of blood
vessel by cutaneous thermo receptors

24.  Superficial heating stimulates the cutaneous
thermoreceptors and it transmit the impulses
from these receptors to the nearby cutaneous
blood vessels
 This release bradykinin and nitrous oxide
which stimulate relaxation of the smooth
muscles which cause vasodialation in the area
where heat is applied.

25.  Cutaneous thermoreceptors pass impulses to
the dorsal/posterior horn of gray matter of
the spinal cord
 It synapse with sympathetic neurons in the
lateral gray horn of the spinal cord to inhibit
their firing and decrease the sympathetic out
put
 The decreased sympathetic activity causes
reduced smooth muscle contraction resulting
in vasodilatation

26.  Increased tissue temperature Activates and
release vasodilatation promoter such as
histamine and prostaglandin which produce
vasodilatation.

27. Reduced blood pressure
 The peripheral resistance is reduced by the
generalized vasodilation, and this cause a fall in
blood pressure
 Rise in temperature also reduce the viscosity of
the blood which reduce the blood pressure
General rise in temperature
 As blood pass through the heated tissues it
carry the heat in to other parts of the body, so if
heating is extensive and prolonged a general
rise in body temperature occurs

29. Change in nerve conduction velocity
 Heat produce a sedative effect
 Increased temperature increases nerve
conduction velocity and decrease conduction
latency of sensory and motor nerve 2m/second
in every 1ºC
 These effects are still under research

30. increased pain threshold
 Application of local heat can reduce the pain by
activation of the spinal gating mechanism and
reduction of ischemia and muscle spasm
 Heat stimulates the sensory receptors of the skin
and it pass information to heat regulating
centers.
 The afferent impulses produced by heat may have
an analgesic effect by acting on gate control
mechanism (counter irritant mechanism).
 Heat induced vasodilatation increase the blood
flow to the tissue and thus reduce the pain
caused by ischemia and further reduction in
muscle spasm that compress blood vessels

31. Change in muscles
 Rise in temperature induces muscle
relaxation and increases its efficiency
 The strength and endurance of the muscle is
found to be decreased during the initial
(30mnts) after the application of deep or
superficial heating
 This initial decrease in muscle strength is due
to the change in the firing rate of type-II
muscle spindle caused by heating.
 After 30 mnts and for the next 2 hours
muscle strength gradually recovers and then
increases to pretreatment level

32.  This can be stated in conforming with Van’t
Hoff equation ‘any chemical change capable
of being accelerated is accelerated by a rise in
temperature’
 Heating of tissues accelerates the chemical
changes (enzymatic activity) in the body ie;
metabolism
 With rise in temperature-all cell activity
increases including cell motility, synthesis
cellular interaction such as cell growth

33.  The increase in the metabolism is greatest in
the region where most heat is produced in
the superficial tissue.
 As a result of increased metabolism there is
an increased demand for oxygen and food
stuffs, and an increased out put of waste
products including metabolites

34. Increased activity of sweat glands
 There is reflex stimulation of the sweat
glands in the area exposed to the heat
 When the heated blood circulates through out
the body it affects the centers concerned with
thermoregulation
 As a result there is increased activity of the
sweat glands through out the body to cool

35.  Increasing the temperature of the soft tissue also
increase its extensibility
 Application of heat before stretching helps to
maintain a greater increase in length after the
stretching force is applied and also the risk of
tissue tearing is reduced.
 It is good to heat the collagenous soft tissue
(tendon, ligament, scar tissue, joint capsule
etc..)before prolonged stretching because it
sustain or maintain the elongation even after
cooling.
 The maintained elongation of this tissues is
caused by the changes in the viscoelasticity of
the fiber

36. Increased ROM and decreased joint stiffness
 Heat is used to increase ROM and decrease joint
stiffness and it is obtained by the increase in soft
tissue extensibility, and less injury in passive
stretch
 We can attain maximum increase in length with
lowest risk of injury at 40 -45°C for 5 to 10 mints
 In case of joint stiffness e.g.-place a joint in warm
water , expose to IRR or paraffin (PWB) it has been
shown that it decrease joint stiffness
 It is due to the increased extensibility and
viscoelasticity of the periarticular structures
including joint capsule and surrounding ligaments
 Apply superficial and deep modalities depends up
on the condition

37. Accelerated or encouragement of healing
 Heating can accelerate healing by increasing the
circulation, enzymatic activity rate, cell activity
and the availability of o2 to the tissue
 Increased circulation ⇨ delivery of blood to tissue
⇨bringing o2 and other nutrients ⇨ removing
waste products
 Any agents that increase circulation is beneficial
during the proliferating/remodeling stage of a
healing

38. Recent hemorrhage
 Heat causes vasodilatation and there will be increased
blood flow to the area and it may cause reopening of
the vascular lesion and it can restart or worse the
bleeding, so heat is contraindicated in recent
hemorrhagic areas
 It should not apply patient who had bleeding in last
48-72hrs
Thrombophlebitis
 Temperature hike may cause increased rate of
circulation which can cause a thrombus or blood clot
to dislodge from the area of treatment and to be
moved to the vessels of vital organs resulting even
death
 Before treatment check the calf for calf swelling.

39. Impaired sensation
 Patients sensation and report about heat is taken
as the primary scale for the measurement of heat,
thus a patient who cannot feel or report that may
get burn easily so heat are not applicable in
impaired skin area. check for sensation (test tube
with h2o)
Malignant tissue
 Here it may increase the growth rate or rate of
metastasis by increasing the circulation to the area
or increased metabolic rate.
 So ask the patient weather he or she is under the
care of any medical management if so what is the
problem.

40.  Do you experienced any recent weight loss or gain
 Do you have any constant pain?
IRR radiation of the eyes
 IRR radiation of the eyes should be avoided
because it may cause optical damage so provide
Opaque or IRR resisted goggles to patient during
treatment session as well as therapist too.

41. Acute injury or inflammation
 It should be applied with caution because
increased tissue temperature can increase
edema and bleeding as result of vasodilatation
and increased blood flow. this may aggravate
injury, increase pain and delayed recovery

42. Pregnancy
 Fetus may be damaged by maternal hyperthermia
 Superficial heating of limbs can be done but
heating of whole body, abdomen area and low back
are avoided
 Pregnant patient should not be immersed in warm
hydrotherapy

43. Impaired circulation
 Areas with impaired circulation may not
vasodialate to a normal degree in response to an
increase in tissue temperature so there may not
have an increased blood flow.
 Decreased skin temperature, poor nails, dry skin,
tissue swelling and ulceration are all signs of
impaired circulation

44. Edema
 Application of thermotherapy has been shown to
increase edema, this is by the result of
vasodilatation and increased circulation by the
raised tissue temperature
Cardiac insufficiency
 Heat can cause both local and generalized
vasodilatation which increase cardiac demand
 A slight decrease in BP and an increase in HR are
normal response to heat
 The treatment should be discontinued if the
patients HR falls or he complains of feeling faint.

45. Metal in the area/implant
 Metal has higher thermal conductivity than body
tissue so remove all jewelry before treatment and
should take care when metal like staple or other
fragments is present in tissue
 In this case mild heat is applied with more
insulation and the area should be check frequently
during treatment for any signs of burning.

46. On open wound
 All forms of thermotherapy except PWB can be
used on open wound with care.
 It should be applied in low temperature with more
insulation
 Hydrotherapy with clean and warm water can be
applied directly to the open wound to accelerate
the healing

47. Over counterirritants applied area
 They cause a sensation of heat when applied
because of the presence of menthol etc…
 It may cause a mild inflammatory changes and a
local vasodilatation, so if apply heat over to this
vasodialated vessels it may not vasodialate further

48.  Excessive heating can cause protein
denaturation and cell death this occurs when
heat is applied too long.
 Protein begins to denature at 45°c and cell death
occurs when heat is maintained at 43°c for 60
mints or 46°c for 7½minutes,
 eg-hot packs which is applied on patients starts
to cool as soon as they are removed from hot
water while comparing with other IRR SWD etc..

49. To avoid burns
 Use superfacial heating agents that gets cooler
during application (hot pack, bottle)
 Limit the initial treating temperature
 Use enough insulation between agent and tissue
 Provide a means for the patient to call you (bell)
Fainting
 Patient may feel faint when heat is applied
 It is due to the low cerebral flow most commonly
cause by peripheral vasodilatation and decreased
blood pressure.

50. Thank you…