When the body has excess heat and is passing the set point, the body releases heat in various ways, one of which is sweat. Heat is lost to the air from the exposed surfaces of the body by conduction, convection and radiation. In man, any change in the temperature balance is regulated mainly by changes in the skin. Sweat causes evaporation from the skin, and this is an effective way of losing heat. The cooled surface of the skin helps release heat together with vasodilation, that is, the widening of blood vessels near the skin, so heat from the blood is radiated out of the body.
Thus, with increased exercise, the internal body temperature will rise, and the body will lose this heat by sweating (decreasing the external temperature) and vasodilation.
Aim: to investigate the change in body temperature (both internal and external) with exercise.
Hypothesis: That with rigorous exercise for 3 minutes (skipping), the core temperature of the human body will increase in temperature, while the external temperature will fall. However fluctuations in the temperature will not be significant, only perhaps 1-1.5°C.
The internal temperature will increase because with exercise, cell respiration increases, additional glucose and oxygen is being transported to muscles (thus increased heart rate), and heat is generated. The internal temperature of the human body can be measured using a digital thermometer placed under the arm.
On the other hand, the external temperature will drop because the body loses heat through sweating – the skin is wet, evaporated, and thus the skin is cooled. The external skin temperature can be measured using a strip thermometer wrapped around the forehead.
After exercise though, the body will restore itself to the original temperatures, as part of maintaining the balance.
Variables
Independent: exercise
Dependent: changes in the internal and external body temperatures
Controlled: type of exercise, duration of exercise, same thermometer used, same exercise ‘environment’ (in the corridor outside the laboratory), same temperature taking environment (in the lab).
Planning B
Apparatus:
- Stopwatch
- Skipping rope
- Strip thermometer
- Digital thermometer
- Antibacterial wash
Method:
- We measured the initial external and internal temperatures of the subject before exercise. The internal temperature was measured by placing the digital thermometer under the arm of the subject. The external temperature was measured by fixing the strip thermometer around the forehead of the subject. The readings were taken.
- The subject then skipped for as much as she could, for 3 minutes. This was considered to be rigorous exercise.
- After 3 minutes, the temperatures were taken again, and results recorded. The temperatures were taken using the same thermometers, measuring from the same place (i.e. if the initial temperature was taken from the left armpit, then the temperature after was also taken from the left armpit). The initial temperatures were taken in the lab, so to keep this factor constant, the temperatures after exercise were also taken in the lab.
- This was repeated, so that each subject exercised twice, with a break in between. Whilst the first person was resting, the partner did rigorous exercise, and the person resting kept time on the stopwatch. Thus, there was a break of approximately 4 minutes between exercise periods (to allow time for reading and recording of results). All skipping took place in the corridor outside the laboratory, a controlled environment. There were no cold winds or heaters interfering (there are no heaters in the corridors), and because of that the corridor should have maintained a constant temperature. Even though the person exercising would radiate heat, the heat would be dissipated through the corridor so it would not affect the temperature of the environment. Also, the experiments were conducted within the span of 15-20 minutes, so the temperature of a room or environment should be relatively stable.
- Between subjects, the thermometers were cleaned using antibacterial wash.
- The difference between the initial temperatures and temperatures after rigorous exercise was calculated.
- To prove the point that the body restores the body to the original temperature (i.e. negative feedback), we also measured the temperatures after 4 minutes of rest following exercise.
Results:
The line graphs below show these tabulated results graphically, which allow for easier interpretation.
It was hypothesized that the internal temperature would increase after exercise. While most of these results support the hypothesis, there is one anomaly in the results which does not support it. In trial 2, the internal temperature of both subjects increased after exercise by at least 0.5°C, mine increased by 0.57°C (from 36.32°C to 36.89°C), and Steph’s increased by 0.56°C (from 34.89°C to 35.45). However in the first trial, temperature measurements indicated that my internal temperature had in fact dropped by 0.86°C. When we took the temperature again, it gave a similar reading. It is uncertain as to why the core temperature would drop, thus, perhaps it can be assumed that it was a problem in the method. Steph’s internal temperature increased, though only marginally, by 0.11°C. If we exclude the anomaly from the data, the average rise in internal temperature is 0.413°C.
It was also hypothesized that the external temperature would fall with exercise. All results gathered with regard to this supported the hypothesis. Indeed, in all trials, the external temperature as measured from the forehead dropped on average 2.5°C. Sweat was evident at the time of the measurement.
The part of my hypothesis that stated the temperature would fluctuate approximately 1-1.5°C is not supported by any of these results. It can be seen that the internal temperatures do not rise or fall more than 1°C, and that the external temperatures fell by much more than 1.5°C.
We can see that indeed, in both these trials, for both subjects, the temperatures ‘after 4 minutes’ (i.e. taken after 4 minutes rest following exercise) are almost always equal to the initial temperatures, ‘before exercise’, despite varying starting temperatures. This supports the hypothesis that the original temperatures would be restored.
Conclusion
Results from this experiment on the whole support my hypothesis, with the exception of one anomaly in the data. It can be seen that the internal temperature rises after rigorous exercise (on average, the internal body temperatures rose by 0.413°C), and the external temperature falls after rigorous exercise (on average, the external body temperature fell by 2.5°C).
My estimates as to how much the temperatures would fluctuate were erroneous; any temperature rise was never more than 1°C, and the fall in external temperature was much more than 1.5°C. In this respect, part of my hypothesis was not supported.
Evaluation
We should have measured the temperature of the environment in which we were exercising and taking temperatures to make sure that the environment was not affecting the readings or changing significantly (we would have hardly noticed because of changes in our internal temperature – it would have just been seen as generally ‘cold’ and so we cannot feel slight changes).
Each reading should have been taken twice to make sure that each temperature taken was accurate. However, taking extra readings would not be as useful because the body temperature may change between the readings. But this would still ensure greater accuracy in the data collected. Perhaps the average of two consecutive readings can be used.
