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# Lung Capacity During Exercise: Balloons and Vital Capacity (page 2)

By John Wiley & Sons, Inc.
Updated on Dec 14, 2010

The volume of air you breathe out after taking a deep breath is much greater than the quantity you exhale after taking in a normal breath. This maximum volume of expelled air is called the lungs' vital capacity. In this activity you will use a balloon and some math skills to determine your vital capacity.

### Materials

Large round balloon

Metric tape measure

Calculator (optional)

### Activity

1. Blow up the balloon a few times to stretch it. Take several deep breaths. When you are ready, take the deepest breath possible, then exhale forcefully into the balloon. Pinch the neck of the balloon so no air escapes, then tie it off with string.
2. Wrap the tape measure around the balloon and measure the circumference in centimeters. Calculate the radius by dividing the circumference by 6.28 (which is pi × 2).
3. Calculate your vital capacity using the formula V = (4/3)3.14 (radius)3.
4. The answer you calculate will be in cubic centimeters (and one cm3 is equal to 1 milliliter.)

### Follow-Up Questions

1. What is your vital capacity?
2. If you had to explain vital capacity to a classmate, what would you say?

2. Vital capacity is the amount of air you breathe out after taking a deep breath.

### Extension

Compare your vital capacity to that of your classmates. Compare your value to other students of different heights, weights, and fitness levels.