I purchased a bag of marshmallows (yes, we're going to eat them) and a box of toothpicks. That's it! We washed hands and put down a clean tissue/napkin/paper towel on each desk. I passed out the marshmallows and toothpicks. I firmly cautioned students about using the toothpicks carefully and appropriately.
Students pushed the toothpick about halfway into the marshmallow and placed this "apparatus" on the inside of their wrist. This took some serious calming down and getting quiet to keep the apparatus in place! The point is to see the toothpick "jiggle" or "bump" with each heart beat.
Results were mixed. Some students had to hunt around for a good spot on their wrist. Once we got going, I timed 15 seconds while students counted their heart beats. We multiplied by four to approximate our heart rate per minute.
As you can see from the pictures, I used large marshmallows. We wondered whether smaller marshmallows might yield different results - would it be easier to see the jiggles? My students would really like to try it out!
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