The Mammalian Diving Reflex

• 3 pans big enough to fit your face into
  • One with cold water between 10 and 15 Celcius
  • One with room temperature water
  • One with warm water
• A willing participant
• A stopwatch

1. Take the pulse of the person you have selected. Use the stopwatch to take their pulses for 1 minute. Now divide the number of beats by 60 to get the number of beats per second.
2. Repeat this 5 times. Average the beats per second to one number.
3. Now have the person stick their face in the room temperature pan of water while counting the number of times their heart beats by fealing their wrist. Use the stopwatch to see how long they are able to stay under water.
4. Divide the number of beats by the number of seconds they were under water to get the number of beats per second.
5. Repeat steps 3 and 4 five times and average the beats per second you get.
6. Repeat steps 3, 4, and 5 with the cold water and the warm water.

What happened to your pulse rate?

Why do you think it happened?