Lung capacity — the total air your lungs can hold in one deep breath — varies between people with different habits, and between boys and girls. You recruit 20 participants of the same age: half are choir members with at least one year of experience, the other half are non-singers and non-athletes. Each person puts on a nose clip, takes one deep breath, and blows as much air as possible into a balloon. You then measure the balloon diameter with a ruler. Choir members inflate their balloons to a larger size than non-singers, and the results also show that boys tend to have greater lung capacity than girls.

Regular vocal practice may strengthen the organs that bring air in and push it back out. To test this, you recruit 20 participants who are all the same age — half are choir members with at least one year of experience, the other half are non-singers and non-athletes. Each person takes one deep breath with a nose clip on, then blows as much air as possible into a balloon. You measure the balloon diameter with a ruler. Choir members inflate their balloons to a larger size than non-singers, suggesting that sustained breathing tasks like singing build lung capacity over time.