Metadata: Teachers’ guidelines, English, energy, heat, temperature, work, human
physiology
1. Excersise and heat (Teachers’ guidelines)
Introduction
Only a minor part of the energy released in the respiration process is used to do actual musclework. A lot of
the released energy is actually converted into heat. To avoid the body from overheating, the blood
circulation to the skin is increased. In this way the heated blood will dissipate heat to the cooler
surroundings, eg. the cool air around the skin. It is possible to measure changes in skin temperature in a
closed and insulated environment (a mitten) where a hand is placed.
Theoretical basis
Glucose and oxygen is transported to the muscles by the blood.
Here it will function as fuel for the muscles, where it in accordance
to the following chemical reaction (respiration) produces energy:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP)
The energy is then used for muscle work as well as other functions.
The more the muscles have to work the more energy will be released according to the respiration process
in the muscle cells. In addition the levels of carbondioxide and water will rise as well as a waste or
biproduct. But only part of the released energy is used for actual work. A lot of the released energy is
actually converted into heat. To avoid the body from overheating, the blood circulation to the skin is
increased. In this way the heated blood will dissipate heat to the cooler surroundings, eg. the cool air
around the skin.
The body has four ways of dissipating heat: Evaporation of sweat, thermal radiation, convection (heating of
the surrounding airflow) and by heatconduction (eg. when the body is in physical contact with a colder
object). In science it will be important to specify that heat is energy transferring between two objects of
different temperature. Heat is always conducted from a place of higher temperature, to a place of lower
temperature. For example, from a heated person and to the cooler surroundings. According to this, heat
can also be transferred from the surroundings and to a person eg. in a sauna. The heated air will have a far
higher temperature than any person inside. This will result in a transport of heat energy from the hot air
and into the body of the visiting person.
T1
Q, varme
T2
Temperatur T1 > T2
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Metadata: Teachers’ guidelines, English, energy, heat, temperature, work, human
physiology
More than two centuries ago, Sir Isaac Newton created “The law of cooling”. This law states that ”the rate
of heat loss of a body is proportional to the difference in temperaturesbetween the body and its
surroundings” (this explains that the bodys’ heat dissipation increases whenever the temperaturedifference
between body and surroundings increases). When en equilibrium between the temperature of the body
and its surroundings is achieved (when T1 equals T2), the heat transfer will stop.
Practical information
For this experiment all which is needed is a sensor which can meassure the skin temperature and a few
pieces of bandaids to fasten the sensor to the palm of the testsubject. It is vital that the sensor is
connectable to either a PC or any kind of datalogging device.
Normally it is not required to calibrate the temperature censors. As well it is not required for this
experiment since we will be focusing on the differences in temperature and not an accurate measurement
of an objects’ actual temperature. The changes in temperature will often be very small and therefore it
migh be usefull to autoscale the y-axis of the co-ordinate system (see the manual for further instructions).
In this way it will be easier to notice small changes in temperature on the produced graph.
Equipment
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Mitten
Bandaids
Sensor, for meassuring the skin temperature
Datalogging device or computer.
Set-up
Connect the sensor to the datalogging device. The mitten and bandaid is prepared for use.
Procedure
The sensor is fastened in the palm of a test subject using the bandaids. If sufficient space within the mitten
allow the person to hold the sensor between two fingers (eg. thumb and indexfinger), he may chose to do
so instead.
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Metadata: Teachers’ guidelines, English, energy, heat, temperature, work, human
physiology
When a stable skin temperature is meassured, the test subject may put on the mitten and the recording of
data can begin. The stabilization of skin temperature will usually occur after a time of 20-30 seconds.
The datarecording (datalogging) will continue for 360 seconds. In this time another stable temperature
should have been reached. The datalogging stops and the test subject may remove the mitten and censor.
Now the test subject will start any kind of physical work, preferably hard work like running up the stairs. He
will continue to do so for four or five minutes until his rate of heartbeats has increased significantly and his
body turns warm or he feels heated.
Whenever our volunteer test subject is done exerciseing and has attained a warm feeling, the above
mentioned measuring technique can be repeated.
Questions
What happens with the temperaturemeassurment when the glove is inserted into the mitten?
What is the explanation for the rise in temperature?
Compare the two meassurements from the datalogging.
How great is the rise in temperature concerning the two different measurements?
Where is the greatest rise in temperature meassured?
Where is the rise in temperature happening faster?
What can be an explanation to the differences in meassurements, which we can observe through the two
graphs produced by the datalogging.
An example of results
The idea of this experiment is to realize how the body transfers heatenergy to the surroundings, and how
an increase in muscle work will increase the heatproduction inside the body. This can be realized by
observing the rise in skin temperature. The figure below tells that the temperature will rise after physical
activity of the test subject. Allow the pupils to state theoretical and factual ideas on to why the rise in
temperature is observed.
This work is licensed under a Creative Commons Attribution 3.0 Unported License. Read about the project: www.dlis.eu/.
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Metadata: Teachers’ guidelines, English, energy, heat, temperature, work, human
physiology
This work is licensed under a Creative Commons Attribution 3.0 Unported License. Read about the project: www.dlis.eu/.
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