Observations and results
Could you hear the volunteer's heartbeat using the homemade stethoscope? Did you find that when they exercised their heart rate increased compared with what their heart rate was when they were resting?
When people exercise, their bodies need more oxygen, and consequently their hearts beat faster and their heart rates increase. This is why you most likely found that when your volunteer exercised, their heart rate increased compared with their resting rate. In addition, genetics, gender, age and health all affect people's heart rates. The rates in people who exercise regularly usually will not increase as much during exercise and will return to a resting rate more quickly after exercise is stopped. Regular exercise strengthens the heart so that it does not need to work as hard.
Although you can determine someone's resting heart rate by counting the number of beats in 15 seconds and multiplying by four to get the bpm, to calculate a heart rate immediately after exercise, it is better to count the number of beats for 10 seconds and multiply that value by six (to get the bmp). Because the heart will quickly slow down after exercise ceases, its rate should be measured immediately after a person has stopped exercising (or while they exercise, if possible).
More to explore
Stethoscope , from KidsHealth
What is a stethoscope and how does a stethoscope work? , from Acoustic Heart
The evolution of an essential tool , from 3M Littmann Stethoscopes
Make Your Own Stethoscope , from Science Buddies
This activity brought to you in partnership with Science Buddies