4. Breathe deeply and forcefully at a rate of about 1 breath/3 second, 20 times (hyperventilate). Time how long you can hold your breath. ______sec

5. Run down the hall and back again or go down to the first floor and come back up quickly. Then immediately hold your breath for as long as possible. Record the time.____________sec.

6. During which procedure could you hold your breath the longest? Why is this so?