Can Your Body Temperature Tell the Time of Day? Find Out with Human Circadian Cycles.

Project Summary

Difficulty	6
Time required	Long (a couple of weeks)
Prerequisites	None
Material Availability	Readily available
Cost	Low ($20 - $50)
Safety	No issues

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Abstract

Have you ever had to adjust to a new time zone and noticed that it takes a while before you start to feel normal again? By shifting your sleep and activity schedule, you have altered the pattern of your body’s circadian rhythms. Human beings, like many other living things, have a number of internal processes that show a distinct circadian rhythm. The most obvious is our sleep cycle, with activity during the day, followed by sleep during the night. Circadian rhythms have also been demonstrated in humans for changes in body temperature, heart rate, alertness, and physical performance in sports. In this human biology science fair project, you will investigate human circadian rhythms by measuring body temperature and reaction time at different times of day.

Objective

In this human biology science fair project, you will measure how body temperature and reaction time vary throughout the course of a day.

Introduction

In order to stay healthy and to function efficiently, living things must coordinate their internal processes with the external world. The most obvious feature of our environment that most creatures have to respond to is the daily cycle of light and dark. Biological processes that follow this 24-hour cycle, such as our sleep-wake cycle, are said to follow a circadian rhythm. One of the best-known circadian rhythms in humans is the daily change in body temperature. We tend to be at our coolest in the early morning and at our warmest in the late afternoon and early evening. Other circadian rhythms include hormone levels, alertness, muscle strength, and heart rate. The controlling regulator for these cyclic processes within the body is thought to be the hypothalamus, which is in the brain.

Overview of biological circadian clock in humans.
Figure 1. Overview of circadian cycles in humans. This diagram depicts some of the circadian patterns that occur in humans. Note that the clock is on a 24-hour cycle, so that 3:30 p.m., for example, is noted as 15:30. The hormone melatonin, which is a key regulator of the internal circadian clock, peaks in concentration at 21:00 (9:00 p.m.). (Wikipedia, 2008.)

Any change in the circadian cycle (such as jet lag and other conditions associated with travel) requires a certain period for readjustment. Jet lag can cause excessive sleepiness and a lack of daytime alertness in people who travel across time zones. Another factor that can affect circadian rhythm is work schedule. For instance, people who work at night are more prone to on-the-job injuries because their circadian rhythm is off-balance with the light and dark times of day.

According to William Garret (see Bibliography), "Reaction time peaks in the early evening at the same time as the maximum body temperature. This is partially because the nerve conduction velocity increases 2.4 meters per second (m/s) for every 1°C increase in body temperature."

Do you think Garret is correct that your reaction time is fastest in the early evening? When do you think it lowest? And how much difference is there? Find out in this human biology science fair project by measuring body temperature and reaction time at various times during the day. Reaction time will be measured using online tests that are based on how fast you respond with your mouse to visual cues on the computer screen. You will then chart your results to graphically show how your temperature and reaction times vary during the course of the day.

Terms, Concepts and Questions to Start Background Research

Circadian rhythm
Core body temperature
Hypothalamus
Nerve conduction velocity
Reaction time

Questions

What physiological processes have circadian rhythms in humans?
Can you think of professions where a slight change in reaction time at different times of the day could be critical?
Research how the time of day affects performance in sports.

Bibliography

Garret, William E. Exercise and Sport Science. New York: Lippincott Williams & Wilkins, 1999, p. 354.
Chudler, E, University of Washington. (2008) Biological Rhythms—Experiment 1: The ups and downs of body temperature. Retrieved August 1, 2008, from http://faculty.washington.edu/chudler/clock.html

To learn more about the biology of circadian rhythms, visit this website at the University of Utah:

Siegel, L. (2008). The Time of Our Lives, Retrieved July 8, 2008, from http://learn.genetics.utah.edu/features/clockgenes/

This test from the British Broadcasting Corporation (the BBC) tests your reaction time by measuring how fast you are able to shoot escaping sheep with a tranquilizer:

British Broadcasting Company. (2008). Sheep Dash! Retrieved August 1, 2008, from http://www.bbc.co.uk/science/humanbody/sleep/sheep/

This website from the Exploratorium Museum, in San Francisco, California, tests your ability to react to a 90-mile-per-hour fastball:

Exploratorium. (2008). Fastball Reaction Time. Retrieved August 1, 2008, from http://www.exploratorium.edu/baseball/reactiontime.html

Materials and Equipment

Thermometer to measure body temperature (digital is best)
A computer with Internet access (so you can use websites that have tests for reaction time)
Lab notebook
Graph paper

Experimental Procedure

In these experiments, you will need to make sure you get the best possible data so that the variation in temperature and reaction time can be measured accurately. Your body temperature may vary from 1 to 2 degrees Celsius. Perform each trial three times and average the results.

Set up a schedule for the times you will measure your body temperature and reaction time. Obviously you will need to work this into your normal schedule for sleeping and school. Be sure to get data early in the morning, say 5:00 a.m., since this is a critical point in your body's temperature cycle.
Taking a reading every three hours is probably sufficient. You might make your measurements at these times: 5 a.m., 8 a.m., 11 a.m., 2 p.m., 5 p.m., and 8 p.m.
Design a data table in your lab notebook to record your observations. It should include the following information: date, time of day, reaction time (three trials), body temperature (three readings), average reaction time, and average body temperature. Keep notes on your methods and observations, such as precisely how you measured your reaction time and body temperature.
Try to control any variables that might affect your readings and give you poor results. For example, avoid drinking hot or cold beverages before you take your temperature.
Lighting and noise levels should be the same or similar during all reaction tests.
Try various thermometers to see which works best. The thermometer should be able to read the temperature at 0.1-degree intervals (or better). It is vital that you take your temperature accurately to be able to document the daily variation. Take your temperature three times each time and calculate the average for each time segment.
To measure your reaction time, use a website with an online test. Here are two examples:

This test from the British Broadcasting Corporation (the BBC) tests your reaction time by measuring how fast you are able to shoot escaping sheep with a tranquilizer: Sheep Tranquilizer Game.
This website from the Exploratorium Museum, in San Francisco, California, tests your ability to react to a 90-mile-per-hour fastball: Hit the Baseball Test.

Record the individual times and the average time for the reaction time trials. Set up the trials any way you like, but once you have a procedure you like, use it consistently. For example, each time you measure reaction time, do one practice test, then record the next three trials for your data.
Repeat steps 2-8 on at least three different days.
Graph your average temperature and reaction times.
Did you observe a change in body temperature or reaction time during the course of each day? If so, how big was the change?
Write a report on your observations. Some things you might include are: How accurately could you measure your temperature? What test of reaction time did you find worked the best? At what time of day was your body temperature highest? At what time of day was your body temperature lowest? Did you see a correlation between body temperature and reaction time?

Variations

Test your friends and family, too (you could send your data table and instructions to them if they don't live nearby). Do you see any differences in circadian rhythms, based on age or gender?
Make more frequent observations, say every hour. Do you observe a small decrease in body temperature in the middle of the afternoon? Some people claim this dip in body temperature can explain cultural behaviors, such as afternoon siestas in Latin countries and the drinking of tea in the United Kingdom.
Research other types of physiological processes that are governed by circadian rhythms and devise ways to test them. Combine this data with the body temperature and reaction time data.
If you are not able to observe a circadian cycle in a physiological process, can you estimate how large the change would have to be for you to observe it (Hint: Look at the standard deviation of your data)? Include the standard deviation data as error bars in your graph.

For more science project ideas in this area of science, see Human Biology & Health Project Ideas.

Credits

David Whyte, PhD, Science Buddies

Last edit date: 2008-11-04 11:40:00

Career Focus

If you like this project, you might enjoy exploring careers in Human Biology & Health.

Medical & Clinical Laboratory Technician
Doctor's need information to decide if a person is healthy or sick, if a baby's earache is bacterial or viral, or if the man next door needs medication to lower his cholesterol and prevent a heart attack. The information often comes in the form of results from lab tests. Medical and clinical laboratory technicians are the people who perform these routine medical laboratory tests, giving the doctors the information needed to diagnose, treat, and prevent disease. Physician
Physicians work to ease physical and mental suffering due to injury and disease. They diagnose medical conditions and then prescribe or administer appropriate treatments. Physicians also seek to prevent medical problems in their patients by advising preventative care. Ultimately, physicians try to help people live and feel better at every age.

Health Educator
Have you ever heard the expression "Prevention is the best medicine"? Prevention is the fundamental work of all health educators. They attempt to prevent illnesses or diseases in individuals or entire communities through education about nutrition, exercise, or other habits and behaviors. Health educators present scientific information in ways that their audience can relate to, and are sensitive to cultural differences. They are the cornerstone of the public health system, improving health and saving thousands of lives by motivating changes in behavior. Registered Nurse
Registered nurses have been called the backbone of our health-care system. Working on the front lines of medical care, they treat patients, monitor and record their condition, help establish a plan of care, educate patients or the public about a medical condition, and provide advice and emotional support to patients’ family members. Registered nurses are highly observant and detail-oriented, and are often the first to catch important and changing signs and symptoms. Many nurses specialize in one or more types of medicine, such as emergency care, hospice, labor and delivery, psychiatry, surgery, or wound care.

Physical Therapist
If you are injured in an accident, suffer a stroke, heart attack, or loss of a limb, or are born with conditions that make it difficult to move your body, then you will often be cared for by a physical therapist. Physical therapists review a patient's medical history, test and measure his or her physical condition (things like range of motion, strength, flexibility, balance, coordination, muscle function), and then develop a treatment plan to meet some physical goals. They coach, motivate, and educate the patient to follow the plan and work on therapies that will restore, maintain, or promote physical fitness and health. Physical therapists also act as advocates, bringing a patient's health needs to the attention of other workers on a patient's healthcare team, such as physicians, speech therapists, or respiratory therapists. Audiologist
On each side of your head is the auditory system, one of the most beautifully designed organs in the human body. The auditory system not only detects sound, but is closely tied to the vestibular system, which helps a person with balance, and knowing how his or her body is moving through space. Audiologists detect, diagnose, and develop treatment plans for people of all ages who have problems with hearing, balance, or spatial positioning. This important work impacts how well a person is able to communicate and function at home, school, and work.

Emergency Medical Technicians and Paramedic
Emergency medical technicians and paramedics belong to a group of healthcare workers known as first responders. They are among the first people to respond to an accident or emergency, providing pre-hospital care for conditions such as heart attacks, strokes, gunshot wounds, childbirth, or falls. Although this work is physically and emotionally demanding, many emergency medical technicians and paramedics enjoy the challenges and the satisfaction of knowing their work is critical in saving lives. Respiratory Therapist
In any medical emergency, health care workers first check a patient's airway and breathing, since oxygen is the first thing needed to survive. Respiratory therapists specialize in treating airway and breathing problems. They help, for example, premature infants whose lungs are poorly developed, or children and adults with asthma or pneumonia. They also treat people who have had heart attacks or who have been in swimming or other accidents. Their critical work helps to provide the breath of life.

Pharmacist
Pharmacists are the medication experts. They advise doctors, nurses, and patients on the correct drug dosage for a patient's weight, age, health, and gender; on interactions between drugs; on side effects; on drug alternatives; on costs; and on ways to give drugs. They also dispense drugs at pharmacies, according to prescriptions, checking for dangerous drug interactions, and educating patients on how to take drugs, what reactions to watch out for, and how long it should take for drugs to work.

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	Medical & Clinical Laboratory Technician Doctor's need information to decide if a person is healthy or sick, if a baby's earache is bacterial or viral, or if the man next door needs medication to lower his cholesterol and prevent a heart attack. The information often comes in the form of results from lab tests. Medical and clinical laboratory technicians are the people who perform these routine medical laboratory tests, giving the doctors the information needed to diagnose, treat, and prevent disease.			Physician Physicians work to ease physical and mental suffering due to injury and disease. They diagnose medical conditions and then prescribe or administer appropriate treatments. Physicians also seek to prevent medical problems in their patients by advising preventative care. Ultimately, physicians try to help people live and feel better at every age.

	Health Educator Have you ever heard the expression "Prevention is the best medicine"? Prevention is the fundamental work of all health educators. They attempt to prevent illnesses or diseases in individuals or entire communities through education about nutrition, exercise, or other habits and behaviors. Health educators present scientific information in ways that their audience can relate to, and are sensitive to cultural differences. They are the cornerstone of the public health system, improving health and saving thousands of lives by motivating changes in behavior.			Registered Nurse Registered nurses have been called the backbone of our health-care system. Working on the front lines of medical care, they treat patients, monitor and record their condition, help establish a plan of care, educate patients or the public about a medical condition, and provide advice and emotional support to patients’ family members. Registered nurses are highly observant and detail-oriented, and are often the first to catch important and changing signs and symptoms. Many nurses specialize in one or more types of medicine, such as emergency care, hospice, labor and delivery, psychiatry, surgery, or wound care.

	Physical Therapist If you are injured in an accident, suffer a stroke, heart attack, or loss of a limb, or are born with conditions that make it difficult to move your body, then you will often be cared for by a physical therapist. Physical therapists review a patient's medical history, test and measure his or her physical condition (things like range of motion, strength, flexibility, balance, coordination, muscle function), and then develop a treatment plan to meet some physical goals. They coach, motivate, and educate the patient to follow the plan and work on therapies that will restore, maintain, or promote physical fitness and health. Physical therapists also act as advocates, bringing a patient's health needs to the attention of other workers on a patient's healthcare team, such as physicians, speech therapists, or respiratory therapists.			Audiologist On each side of your head is the auditory system, one of the most beautifully designed organs in the human body. The auditory system not only detects sound, but is closely tied to the vestibular system, which helps a person with balance, and knowing how his or her body is moving through space. Audiologists detect, diagnose, and develop treatment plans for people of all ages who have problems with hearing, balance, or spatial positioning. This important work impacts how well a person is able to communicate and function at home, school, and work.

	Emergency Medical Technicians and Paramedic Emergency medical technicians and paramedics belong to a group of healthcare workers known as first responders. They are among the first people to respond to an accident or emergency, providing pre-hospital care for conditions such as heart attacks, strokes, gunshot wounds, childbirth, or falls. Although this work is physically and emotionally demanding, many emergency medical technicians and paramedics enjoy the challenges and the satisfaction of knowing their work is critical in saving lives.			Respiratory Therapist In any medical emergency, health care workers first check a patient's airway and breathing, since oxygen is the first thing needed to survive. Respiratory therapists specialize in treating airway and breathing problems. They help, for example, premature infants whose lungs are poorly developed, or children and adults with asthma or pneumonia. They also treat people who have had heart attacks or who have been in swimming or other accidents. Their critical work helps to provide the breath of life.

	Pharmacist Pharmacists are the medication experts. They advise doctors, nurses, and patients on the correct drug dosage for a patient's weight, age, health, and gender; on interactions between drugs; on side effects; on drug alternatives; on costs; and on ways to give drugs. They also dispense drugs at pharmacies, according to prescriptions, checking for dangerous drug interactions, and educating patients on how to take drugs, what reactions to watch out for, and how long it should take for drugs to work.