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Department of Biophysics, Medical Faculty, Masaryk University in Brno
1
Lectures on Medical Biophysics
Physical Therapy
ultrazvuk_v
Hubbard Hydrotherapy Tank,
Carlos Andreson, Watercolour, 1943

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Lecture outline
Main methods of physical therapy:
̶Therapy by mechanical treatment
̶Non-electric thermotherapy – (heating and cooling, hydrotherapy)
̶Electrotherapy
̶Ultrasound therapy
̶Magnetotherapy
̶Phototherapy

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Therapy by mechanical treatment - examples
Massages – manual or instrumental
Changes in blood circulation, muscular relaxation
Rehabilitative exercises
increase of body strength and mobility, psychical effects, improvement of body posture
massage6small Lecebny_telocvik

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Thermotherapy
The application of heat is (from biophysical point of view) an intervention in the body
thermoregulation. Heat can be delivered to the organism (positive thermotherapy), or taken away
from the organism  (negative thermotherapy).
The body response depends on:
- the way of application - heat conduction, convection or radiation (see electrotherapy and
phototherapy)
- the intensity, penetration ability and duration of the heat stimulus. Nonelectric thermotherapy
causes mainly changes of body surface temperature (to depths of 2 - 3 cm), with electrotherapy we
can heat deeper tissues.
- the size and geometry of the application area in the case of local application: The tissue
temperature increases when the heat input from outside exceeds the heat output. Cylindrical body
parts are heated faster when the radius is small. Considering only conduction, the resistance to
heat flow increases linearly with the thickness of tissue layers. In cylindrically shaped tissues
it increases non-linearly.
- the patient’s health (ability of thermoregulation).

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Thermotherapy
The following sources of heat are used in thermotherapy:
a)Internal (heat produced by the organism itself).
b)External. Considering the origin and transfer of heat, the thermotherapeutic methods can be
divided into five main groups based on:
- heat conduction
- heat convection
- radiation
- high-frequency electric currents
- thermal action of ultrasound

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Heat conduction
Mainly packs and compresses. According to the extent of the covered body part, they can be total or
partial, according to the temperature hot, indifferent or cold, and wet or dry.
The compresses can be dry (blankets, bottles), peloids (mud) and paraffin. Their temperature ranges
from 45 to 55 ºC in dry compresses up to 60 - 77 ºC in paraffin compresses.
Thalasso-Views mud3

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Heat convection – hydrotherapy
̶hydrotherapy encompasses, besides heat effects, also mechanical action (buoyancy, hydrostatic
pressure, impacts of water movement). It acts mainly on the cardiovascular system, vegetative
nerves and psychology. Heat helps muscles to relax, reduces pain, accelerates resorption of
oedemas. The procedures differ from each other in the way of heat transfer, in the ratio of
conduction and convection, and in the degree of homogeneity of heat flux:
̶cold (less than 18 °C), cool (18 – 24 °C), tepid (24 – 33 °C), warm (33 – 36 °C) or hot (37 – 42
°C).
̶Or: hypothermic (10 - 34 °C, 5 min.), isothermal (34 - 36°C, 20 - 30 min), hyperthermic (37 -
42°C, short duration).
̶The effect of the whole-body bath is given mainly by the surface body temperature. After
immersion, the body surface is exposed to the actual medium temperature until thermal equilibrium
is formed in several millimetres thick water layer, and the effective bath temperature starts to
act.  Disturbing the layer prevents stabilisation of the effective temperature, thus the patient
should not move during the bath.

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Whirling baths, underwater massages, hot and cold water jets
hydrotherapy1
For upper and lower limbs moderately hyperthermic – increasing blood supply and metabolism, skin
receptors activated
Alternative application of sharp hot and cold-water jets – a method with outstanding activation
effect.
http://www.alaid.cz/img/pages/35i3big.jpg
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.manes-spa.cz%2Fcs%2Flecba%2Fprocedury&psig=AO
vVaw2eGqjcF-ctTDPfDkwC7OUG&ust=1701979704263000&source=images&cd=vfe&opi=89978449&ved=0CBEQjRxqFwoT
CNCHqtXO-4IDFQAAAAAdAAAAABA5
http://www.nawellness.cz/zobrazit-obrazek/--13113.jpg PROCEDURY

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Sauna
Effects of hot (80 - 100°C) air of low relative humidity (10-30%) are utilised, followed by cooling
in cold water. Outstanding tonic action. Steam bath: about 45°C, up to 100% humidity. IR sauna
Sauna http://www.finskasauna.cz/img/photo/365.jpg

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Cryochamber
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http://img1.hyperinzerce.cz/x-cz/inz/5302/5302196-kryokomora-za-bezkonkurencni-cenu-1.jpg
Action of dry very cold air (up to -160°C) during some minutes followed by aerobic exercise.
http://kolo.cz/media/2011/05/27/kryokomora-na-vlastni-kuzi.jpg

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Cryocauter
•Tissue ablation using a stream of cooled media or an instrument tip cooled with e.g. liquid
nitrogen, CO2, N2O, special gases-70°C
•cervical tumour

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Electrotherapy
Electrotherapeutic methods utilise
- Direct electric current (galvanotherapy, iontophoresis)
- Low-frequency alternating current or short impulses of direct current (stimulation)
- High-frequency alternating current (diathermy)
- High frequency electromagnetic radiation
Temná historie elektrošoků: Teď jimi prochází vdova po Brabcovi (†63)! | Ahaonline.cz

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Conduction of electric currents in tissues
̶Passage of electric current through human body obeys the Kirchhoff’s laws. Tissue resistance
varies. The ions (Na+, K+, Ca2+, Mg2+, Cl- ) are current carriers.
̶We can distinguish two types of tissue electric conductivity. Cytoplasm and intercellular medium
behaves like conductors whose resistance does not depend on frequency. Membrane structures have
properties of capacitors, i.e. their impedance Z depends on frequency:

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Resistivity (r, rho) of tissues
R is the electrical resistance of a conductor (measured in Ω)
l is the length of the conductor (measured in m)
A is the cross-sectional area of the conductor (measured in m2)

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Tissue polarisation
̶The electric charges present in tissues are not always free, they are often bound to
macromolecules which are an integral part of cellular structures, and their mobility is limited.
The macromolecules behave like electric dipoles – variously oriented – their dipole moments are
mutually compensated.
̶The electric dipoles are oriented according to the direction of the outer electric field when it
is present – their polarisation occurs. So an inner electric field of opposite polarity arises, and
the intensity of the outer electric field is lowered. This turning of polar molecules gives rise to
the so-called displacement current. Permittivity e is a measure of this ability.

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Effects of direct electric current (galvanotherapy, iontophoresis)
Continuous direct current (DC) does not stimulate but can change conditions for that. This effect
of DC is called electrotonus and is used in galvanotherapy.
ØAround cathode (-) an increase of stimulation of motor nerves occurs = catelectrotonus.
ØAround anode (+) a decrease of stimulation of sensitive nerves occurs = anelectrotonus.
ØApplication in electrotherapy.
Electrokinetic phenomena – movement of ions or solvent in electric field – iontophoresis – ions are
transported inside the body.
electra Home-Use Iontophoresis Machine for Hands and Feet | Sweat Guard – SWEAT GUARD®

•< 1 Khz, pulsed direct current
•Pacemaker
•Defibrillator (AED)
•Electroconvulsive therapy
•
Effects of direct electric current
undefined Přenosný manuální externí defibrilátor. Local doctor implants one of the first wireless,
dual chamber pacemakers
https://1884403144.rsc.cdn77.org/foto/sarka-rezkova/Zml0LWluLzEyMDB4OTk5OS9maWx0ZXJzOnF1YWxpdHkoODU
pOm5vX3Vwc2NhbGUoKS9pbWc/3243382.jpg?v=0&st=oT7E-9ywbgCGxZYWKiYJxCWlwoWGyKTgp_fookcK9QI&ts=16008120
00&e=0
https://cdn.hswstatic.com/gif/electroconvulsive-therapy-2-orig.jpg
How Electroconvulsive Therapy Works | HowStuffWorks

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Low-frequency AC - electric stimulation
̶The excitability is a general feature of living systems. In mammals, it is best expressed in nerve
and muscle tissue. Electric stimulation - ability of tissue to react on electric stimuli. The
direct current has stimulating effects only when suddenly changed.
̶The stimulation is a threshold phenomenon, it occurs only after a specific threshold intensity has
been reached - the rheobase.
̶The time factor is more important for quantification of stimulation ability: Chronaxie is a time
interval necessary for induction of stimulation at the current intensity equal to a two-fold value
of rheobase.
̶Any skeletal muscle has a characteristics chronaxie. Changes of chronaxie help to determine the
degree of excitability impairment and also the degree of muscle impairment.
The shortest chronaxie is found in skeletal muscles  (< 1 ms),  heart muscle (5 ms), the longest
one have smooth muscles (50-700 ms). The chronaxie can be  read from the so called I/t curve, the
dependence of current pulse intensity on its duration.

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ØThe skeletal muscle with normal innervations reacts differently on stimulation by electric
impulses with rapid onset (rectangular impulses) and with slow onset (triangular impulses).
ØIn short impulses below about 10 ms, the I/t curve has the same shape.
ØFor longer rectangular impulses the excitability does not change (curve 1) but the excitability
for triangular impulses lowers (curve 2).
ØThe muscles with damaged innervations (denervated) are not excitable by very short impulses.
However, their excitability for long impulses with slow onset increases (curve 3). So arises area
of selective excitability („OSD“), which allows stimulation of denervated muscles without
stimulation of healthy muscles.
The I/t curve

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Low-frequency AC - frequency dependence of stimulatory action
̶In very low frequencies (< 100 Hz), the stimulatory action grows linearly with frequency. In high
frequencies, the growth of stimulatory action becomes smaller and changes in decrease. In the range
of 500 - 3000 Hz, the threshold value of stimulating current depends on Öf. The stimulatory action
starts to decrease above 3000 Hz and at about 100 kHz disappears fully.
̶High frequency currents have no stimulatory action because the duration of one period is much
shorter than the shortest chronaxie. They have no electrochemical effects either.

The frequency, length of exposure and direction of passage through the human body are important.The
greatest risk of fibrillation is 30-100 Hz Safe current - AC 3.5 mA; DC 10 mA
•0.5 to 1 mA - threshold of electric current perception
•1 to 8 mA - nerve irritation, blood pressure rise
•6 to 15 mA - causes tetanic spasm, person cannot Relax
•25 mA - tetanic spasm of the respiratory systém
•60 mA - ventricular flutter (fibrillation), transient cardiac arrest
•above 80 mA - usually permanent cardiac arrest
•above 100 mA - possible burns, defibrillator area
https://www.zachranny-kruh.cz/image.php?idx=292734&mw=250&mh=188 AKUTNĚ.CZ Electrical injury figure
1
https://jmedicalcasereports.biomedcentral.com/articles/10.1186/s13256-019-2231-4
https://www.akutne.cz/res/algorithm/000105/anot-uraz-elektrickym-proudem_5465c89505bc5.jpg
Negative effects of electric currents
Q = U·I·t

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Electrocauter
AMS Trading
•Tissue coagulation by thermal effects of an electric current with a frequency of 200 kHz – 3.3 MHz
and a power of 750 W (60-120 °C)
̶Cutting - higher frequency
̶Coagulation - stop bleeding - lower frequency

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Electrostimulation
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The stimulating effects depend on the amplitude, frequency, shape and modulation of pulses, and the
kind of tissue!!!!!

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Thermal effects of high frequency (HF) currents
̶Mechanism of the HF currents action is based on transformation of the absorbed electric energy
into heat Q according to Joule’s law:
                         Q = U·I·t
    where U is voltage, t is the time of current I passage. This mechanism of heat production
depends on the way of HF currents application.
ØDielectric heating (due to dielectric losses) takes place when applying currents by means of a
capacitor field.
ØWhen using induction fields, heat is produced by the so-called eddy currents.

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Utilisation of high-frequency (HF) electric currents
̶In the case of alternating electric HF currents (>100kHz), the heat effects dominate totally. The
heat originates directly in tissues due to dielectric heating, eddy currents or absorption of
electromagnetic energy.
̶For HF therapy, international agreements specified the following frequencies:
̶Short-wave diathermy (27.12 MHz, i.e. wavelength of 11.06 m),
̶Ultra-short-wave diathermy 433.92 MHz (69 cm),
̶Microwave therapy 2 400 or 2 450 MHz (12.4 or 12.25 cm) .
̶HF therapy makes possible deep heating.

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Three ways of application of HF currents:
̶1. The tissue is connected in the electric circuit as a resistor by means of contact electrodes –
classical diathermy. It is not used in practice today.
̶2. Tissue is connected as dielectric placed between insulated electrodes – heating in the
capacitor field. The heat produced is proportional to the dielectric loss. Amount of heat arising
in subcutaneous fat tissue is lower than in the muscles.
̶3. Use of eddy currents in magnetic field of a coil – inductive heating. An insulated cable is
wound round a limb, or a coil is laid to the body. The skin is less heated, 2 cm thick muscle layer
lowers the heating to one half.

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Different ways of HF diathermy
Application of HF currents
(a- condenser field, b- inductive, c- microwaves)
47

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Short-wave diathermy – heating in capacitor field
diatermie http://berta.yconix.com/uploads/images/procedury/diatermie.JPG

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Microwave therapy
Source: magnetron. The oscillations of electromagnetic field are led to an emitter - a dipole with
a reflector. 1 cm of muscle is enough to lower the intensity to one half, the relation between heat
production in the skin and the muscles is almost equalised. Microwaves put electrically charged
particles (ions, dipoles) into oscillatory motion which is transformed into heat by friction.

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Microwave diathermy
brd-dthm
(older type)
mt3d

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Potential risks of microwave and radiofrequency radiation
̶Mainly thermal effects.
ØMicrowave sources
ØRadars
ØCell phones
ØRadio and TV transmitters
ØElectric mains
ØTrolley lines (wires)
̶Some studies showing carcinogenic effects of microwaves or low-frequency electromagnetic fields
were not verified sufficiently, but it is prudent to reduce exposures.

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Ultrasound therapy
̶Ultrasound therapy is based on biological effects of ultrasonic oscillations which are not
electric. Despite of that, this therapy is sometimes included in the list of electrotherapeutic
methods.
̶An ultrasound (US) therapeutic system consists of two main parts: generator of HF electric current
and the application probe, the US source itself, which consists of a piezoelectric transducer.
̶In therapy, f = 0.8 - 1 MHz is used, sometimes up to 3 MHz, with intensity of US - typically 0.5 -
1 W·cm-2 . Exposure time is 5 - 15 min., in 5 - 10 repetitions. US can be applied continuously or
pulsed.
̶The main therapeutic mechanism is high-frequency massage of tissue. Additional effects are tissue
heating (causing hyperaemia) and some  physico-chemical effects.
̶Acoustic coupling between the probe and the skin is secured by a gel (local application) as well
as water (underwater application).
̶Main indications of US therapy: chronic joint, muscle and neural diseases. Limited success is
reported in healing wounds after surgery, healing injuries and varicose ulcers.

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Thermal action of ultrasound
In US therapy, thermal dissipation of acoustic energy takes place. Tissue heating depends on
physical properties of tissue and its blood supply. The highest heating appears at the interfaces
between tissues of very different acoustic impedances.
The thermal action of US cannot be considered without respect to other healing mechanisms
(micro-massage etc.)

Piezoelectric effect
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http://res.mindray.com/en/media/products/ultrasound/M9/1.jpg
Direct piezoelectric effect
•When a piezocrystal is deformed, positive and negative ions in the crystal lattice are displaced
and an electric charge is generated on the crystal surface.
•The magnitude of the charge is directly proportional to the deformation of the crystal.
•The direct effect is used to detect ultrasonic waves.
Indirect piezoelectric effect
•By applying an electric voltage to the surface of a piezocrystal, ions in the crystal lattice are
displaced and the crystal deforms.
•The amount of deformation is directly proportional to the applied voltage.
• The indirect effect is used to generate ultrasonic waves.

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Zápatí prezentace
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̶
https://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/Piezoeffekt350px_clr.gif/300px-Piezoeffek
t350px_clr.gif

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Ultrasound - THERAPY
ultrazvuk_v sonic15 sonopuls491UZ sonopuls591UZ

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works on the principle of longitudinal ultrasonic oscillation at a frequency of up to 55 kHz. This
generates energy at low temperatures between 50 and 100 °C. It enables cutting and coagulation of
soft tissues, blood vessels and sealing of lymphatic pathways in an instant. Bleeding is 4 to 6
times less with the harmonic scalpel than with other surgical methods. Less thermal damage to the
tissue.
Výsledek obrázku pro harmonicky skalpel Výsledek obrázku pro harmonicky skalpel Innolcon Y16-E
/ Ultrazvukové generátory / Elektrochirurgie / Produkty / NIMOTECH, s.r.o.
Ultrasonic Scalpel (harmonic scalpel)

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Zápatí prezentace
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Cavitation
̶Ultrasonic cavitation means the disruption of the continuity of the liquid medium by the
ultrasonic wave, associated with the formation of gas (cavitation) bubbles.
̶Resonant cavitation: the bubbles periodically oscillate with the frequency of the ultrasound. The
amplitude of the oscillations occurs at a frequency close to the bulk resonance of the bubbles
(depending on the size of the bubble).
̶Collapse cavitation: bubbles collapse rapidly. Their collapse is accompanied by a sharp
temperature rise (up to 103 K) and a strong pressure shock (up to 106 Pa). During the collapse, the
water vapour in the bubble dissociates to form free radicals.
http://eswt.net/wp-content/uploads/2011/10/cavitation.gif

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Effects of magnetic fields - magnetotherapy
̶Basic concepts: magnetic fields: static, alternating and pulsed. Homogeneous and non-homogeneous
magnetic fields.
̶Magnetic flux density B depends on the magnetic permeability of the medium m:
m = mr.m0
̶Ferromagnetic substances - mr >>1.
̶Diamagnetic substances - mr is slightly lower than 1
̶Paramagnetic substances - mr is slightly higher than 1.
(m0 is permeability of vacuum – 4p·10-7 N·A-2)
̶Body tissues are composed almost only from diamagnetic and paramagnetic substances. Magnetic
fields can induce electric voltages and currents in biological medium (due to action of Lorentz
force on moving electrical charges, or by action of Faraday force in varying magnetic fields). The
induced voltages are, of course, substantially lower than the membrane potentials.

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Magnetomechanical and magnetochemical effects
̶In a strong mg field, the diamagnetic and paramagnetic molecules orient themselves to minimise
their free energy. In non-homogeneous fields with big gradients, a translation movement of
ferromagnetic compounds takes place (in living organisms negligible). A strong mg field (over 1 T)
would reduce the flow rate of laminar streaming in a tube.
̶Further, it is necessary to consider indirect action as well, mediated by free radicals arising
because of magnetochemical reactions.
̶We can say that a stable magnetic field of high intensity inhibits metabolic processes, but a
varying one stimulates them. These changes are transient.
̶The interactions of magnetic fields with human tissues are utilised in both diagnostics and
therapy. Magnetotherapy is an example of healing procedure. Magnetic stimulation of brain can be
used both in diagnostics and therapy.
[USEMAP]

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Magnets in medicine
Transcranial magnetic stimulation
biotesla_2000 BiStim Module mesmtub
Magnetotherapy
Biomagnetism quackery of Franz Messmer 200 years ago

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Phototherapy
Ultraviolet (UV), visible (VIS) and infrared (IR) light sources are commonly used in medicine,
namely in physical therapy.
brdk-uvl solux
[USEMAP]
http://www.symbinatur.com/obrazky/texty/1273/1.jpg
http://www.skinea.cz/uploads/images/180/large/000106-180.jpg

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Light radiation
̶ultraviolet  (UV)  1- 380 nm: UV-A 380 - 315 nm
UV-B 315 - 280 nm
UV-C 280 - 190 nm
̶visible (VIS) 380 - 780 nm
̶infrared (IR) 0.780 - 1 mm: IR-A 0.78 – 1.4 µm
    IR-B 1.4 – 3.0 µm
     IR-C 3.0 µm – 1.0 mm
̶From a practical point of view, the ultraviolet range begins from the wavelength of 190 nm. The
spectral range 1 - 190 nm is so called vacuum UV radiation. It is attenuated strongly even by air
and hence its biological effects are rare.

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Sources of light
̶The only natural source is the Sun.
̶The other sources are artificial and each of them emits  only one part of the optical spectrum:
ØHot objects. The wavelength of radiation depends on source temperature, its spectrum is
continuous. Light bulbs and various sources of radiant heat.
ØLuminescent sources (fluorescent lamps and tubes). They are based on excitation processes in atoms
and molecules. Spectrum of these sources can consist of individual spectrum lines.
ØBoth these sources emit non-coherent radiation.
̶The only artificial source of intense coherent light is the laser.

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1919%20fremont%20street%20neon
Sources of visible light
lamps laser-coh
http://solarscience.msfc.nasa.gov/predict.shtml
http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif

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Molecular mechanisms of biological effects of light
̶Energy of single atoms depends on its electron configuration. Delivery of energy causes electron
jumps to higher energy levels (DEe) – an excited state arises. Absorption spectrum is not
continuous. The excitation takes place mainly in the valence shell.
̶Energetic states DE of a single molecule are, in principle, sums of electron energies
DEe corresponding  to the electron configuration, vibration energy DEn  and rotation energy DEr :
DE  =  DEe +  DEn  +  Der
̶All the three kinds of energy are quantised. The action of the radiation depends on photon energy.
The lowest energy have photons of IR-C, it corresponds to the changes of rotation energy of
molecules. The energy of IR-B and IR-A photons can influence both the vibration and rotation of
molecules. The energy of VIS and UV photons can influence rotation, vibration and also electron
configuration.

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Interaction of laser radiation with tissue
̶The effects of laser radiation depend on reflectance, diffusion, absorption and transmission in
the biological environment.
̶The absorbed light laser photon energy is incorporated into the energy processes in the irradiated
tissue according to the achieved energy density values and the exposure time.
Laser Therapy - PhysioPlus Health Group

Effects of LASER light
During the anti-inflammatory effect, the low-power laser activates the natural repair processes by
which the body reacts to the ongoing inflammation. The chemotactic activity of the cells
(lymphocytes, monocytes, fibroblasts and polymorphonuclear cells) involved in the anti-inflammatory
response of the organism is increased.
48

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Effects of visible light
Photosynthesis ?biochemistry
Photoreception ?biophysics of vision
S_rhodopsin 180px-Simple_photosynthesis_overview_svg
Photosynthesis splits water to liberate O2 and fixes CO2 into sugar
From Wikipedia, the free encyclopedia

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Molecular effects of ultraviolet radiation
̶Considering compounds of biological importance, the most sensitive are those with conjugated
double bonds.
̶In proteins, the most sensitive amino acids are tyrosine and tryptophan. (abs. maximum around 280
nm).
̶In NA, the N-bases are sensitive. Their absorbance is higher than the absorbance of proteins,
maximum at 240-290 nm.
̶UV radiation penetrates only into the surface layers of the skin
̶The skin effect of UV light manifests itself as reddening – erythema – followed by melanin
pigmentation Þ protecting mechanism against further penetration of UV. Synthesis of vitamin D which
controls metabolism of Ca and P (its lack causes rickets - rachitis), is an important positive
effect of UV light. We cannot also exclude the carcinogenic effect of UV since almost 90% of skin
cancer appears on uncovered areas of the skin.

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Sources of ultraviolet radiation
̶Sun
̶Mercury discharge tube (used in medicine)
̶Hydrogen or deuterium discharge tubes (used in research)
̶Xenon lamp
̶Electric arc, lightning etc.
̶Some lasers

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Penetration of UV radiation
fig1
[USEMAP]

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Effects of ultraviolet radiation on living organisms
Sunburns - erythema
Effects on eye: blepharospasm (uncontrollable closure of eye lids) – originates due to damage of
cornea by UV radiation. Þ protection by goggles with UV filter. Lens cataract can arise (Fig.↓)
UV-C with wavelength below 280 nm has outstanding bactericidal action. Þ sterilisation of labs,
special boxes and surgery rooms.
sunburn cataract%20eye 23promo1

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Sources and effects of infrared light
̶All the three ranges of IR radiation have thermal effects.
•IR-A is involved in sun light. It passes through glass and is only little absorbed by water.
•IR-B is emitted from various lamps and discharge tubes. It passes through glass but is well
absorbed by water.
•IR-C is emitted from heater, hot bodies, humans…. Absorbed by glass and water.
̶Almost all IR radiation is absorbed by skin. It causes local vasodilatation and thermal erythema
which looks like diffuse red patterns and, in contrary to the erythema caused by UV light, its
duration is short. Pigmentation is very weak. The irradiation by IR light, however, increases skin
sensitivity to the UV light.
̶A long exposure of eyes to the IR radiation can cause in some professions (glass-blowers,
founders, smelters, steelmen etc.) the so called heat cataract (opacity of the lens).

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IR radiation heat transfer
Heat action of the visible and IR light from artificial sources:

̶Lamp boxes – radiation heat in enclosed space. Skin receptors are stimulated, whole-body heating
occurs.
̶IR lamps: Solux, Sirius -  high-power lamps with blue or red filters, radiators of IR light. The
radiation is absorbed mainly in body surface. Used mainly in dermatology, ORL and dentistry.  Skin
receptors are stimulated, suggestive feeling of heat, reflex vasodilatation and muscular relaxation
takes place.

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Lowering light intensity to 35 % of original value
newsf17
Penetration of IR radiation
http://www.depilazione.net/news4.htm

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Thermal Erythema
Thermal erythema – erythema because of excessive use of electric pad -
BACK: erythema ab igne
http://dermatlas.med.jhmi.edu/derm/Display.cfm?ImageName=EAB

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Summary – effects of light
fig13a

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Author:
Vojtěch Mornstein
Content collaboration and language revision:
Ivo Hrazdira, Carmel J. Caruana
Last revision September 2024