Name ______
The Rule of Threes – 30 Informal Points
Introduction
With each breath, we take in oxygen that feeds our cells and fuels the production of energy. Water nourishes our tissues and helps regulate the level of chemicals in the body. The carbohydrates, proteins and fats that we ingest in food supply energy, as well as build materials the body uses for growth and maintenance. Each of these resources is vital to human survival. But how long can the body last when one of these resources reaches a critical low?
In the last activity, you learned about the incredible story of Mauro Prosperi. Somehow, he beat the odds and managed to survive under unimaginable conditions. The human body has the ability to adapt to internal and external changes and to conserve valuable resources. In this activity, you will continue your exploration of fuel and power in the body and debate the validity of a survival rule: The Rule of Threes. You will discuss how factors unique to the person or the environment may help that person survive in the absence of vital resources or, sadly, push him/her closer to the edge.
Procedure
Many survival guidebooks reference the Rule of Threes, rough estimates for how long a person can last without key resources. This rule states that a human can live:
o 3 minutes without air
o 3 days without water
o 3 weeks without food
1. Discuss why these rules may not apply to every person in every environmental situation in the space below.
In general, a human can live 3 minutes without air (oxygen), 3 days without water, and 3 weeks without food. However, this is simply a generalization. Age, health, physical fitness, and environment all contribute to these numbers. For example an elderly person with failing health would have smaller numbers, whereas a professional athlete would most likely have larger numbers.
2. Use the Internet to research factors in the environment that may speed up or slow down this “time to empty.” Fill in the table below to organize your thoughts.
Rule of Three / Factors that will Speed Up / Factors that will Slow Down3 Minutes without Air / High elevation / Freezing cold water
There have been instances of people “downing” and being underwater for 30-45 minutes, but surviving
3 Days without Water / Heat and humidity will cause one to become dehydrated faster / Stable room temperature
Access to food
3 Weeks without Food / Intense physical activity
Being in an extreme environment, such as frigid cold / Low physical activity
Access to water
Being in a room temperature environment
3. Use the Internet to research factors unique to the individual that may speed up or slow down this “time to empty.” Fill in the table below to organize your thoughts.
Rule of Three / Factors that will Speed Up / Factors that will Slow Down3 Minutes without Air / Low physical fitness
Old Age
Large body mass / Physical fitness
Young age
Playing a wind instrument
Low weight/body size
3 Days without Water / Low physical fitness
Old Age
Large body mass / Physical fitness
Young age
Low weight/body size
3 Weeks without Food / Low physical fitness
Old Age
Small body mass / Physical fitness
Young age
Large weight/body size
4. Think back to the story of Mauro Prosperi. Did the high temperature of the desert impact his body’s key resources? Describe in the space below.
Yes, the hot temperature / dry heat caused him to become dehydrated more easily.
5. Mauro was 39 years old. Do you think he would have lasted as long as he did if he were in his 60s? Why or why not? Explain in the space below.
No, as the body ages the systems slowly deteriorate and a harsh environment is more devastating.
6. Visit the Discovery Channel – Human Body: Pushing the Limits website at https://www.youtube.com/watch?v=7Wbs6DJkwEU .
Conclusion Questions
1. How did the swimmer in the video prepare for the energy demands he was about to place on his body?
He purposely gained weight both as fat and muscle to have a “store” of energy to draw upon and be used as fuel. He gained enough fat so that fat would be burned and not muscle.
2. How did his body manage his fuel reserves? What macromolecules did his body look to first for energy? What did his body do when this resource ran out?
Carbohydrates are burned first, then fat, then muscle. It’s not good to burn muscle because not only do muscles get smaller and weaker, but organ damage, such as the heart, occurs.
3. List the body systems that were affected during Mauro Prosperi’s journey across the desert. Describe how you think he was able to last as long as he did. Think about how his body would deal with his environment and how Mauro could work to conserve his energy resources.
His nervous system sent out signals to the other body systems to reduce the amount of energy they used and to conserve water to essential body systems like the urinary system. The urinary system's hormones, ADH and aldosterone would be limited, thus conserving the amount of water his body stored. Lastly, the endocrine system would send out signals to the hormones ADH and aldosterone to regulate the urinary system itself.
4. What type of meal would a long distance runner or swimmer want to eat the night before a grueling race? Explain your choices.
They would want to have a meal rich in sugars, such as glucose, for fast energy. Also, it would be beneficial to eat polysaccharides like starches (pasta) which would then be stored in the muscles and liver in the form of glycogen and the body would immediately be able to use that energy during the race.