Before you begin, you should practice doing a proper jumping jack with your class. Tell children to start with their hands by their sides. To perform a jumping jack, their legs will go out and their arms will go over their heads and clap. Perform one jumping jack together to make sure children are able to coordinate their movements. Repeat as many times as necessary until children are able to perform a jumping jack properly without adult help.
In order to plan a science activity with jumping jacks, you will need to discuss what the heart does with your class. Tell them that their hearts pump blood and oxygen, or air, to all of the other parts of their bodies. Exercise makes the heart beat faster, which makes the heart pump even more blood and oxygen to the rest of the body. Once children understand this concept, split the class into groups of two. Give each child in the pair a chance to wear the stethoscope and listen to their partner's heartbeat. Ask children to count the beats they hear while you set a stop watch for thirty seconds. At the end of thirty seconds, help children write down the number of heartbeats they heard on a piece of paper. Explain that this will be their resting heart rate, when the heart is not beating fast.
Have children do 10 to 15 jumping jacks together and try one more time to listen to their partner's heart beat. Explain that since jumping jacks are an aerobic exercise, it will make their hearts work harder and pump more blood and oxygen to other parts of the body. Help children count and record the number of beats they hear after the jumping jacks and explain that this is their exercise heart rate.
Once all the numbers have been recorded, make a list of all the children's resting heart rates as well as the exercise heart rates. Display the results on a large poster board and point out the differences in heart rates with the children. Ask the children simple questions that can be answered by looking at the chart, such as who had the fastest resting heart rate or who had the fastest exercise heart rate. Leave the results displayed in your classroom for children to investigate further on their own. Allow children to conduct the jumping jacks experiment again and compare their results to the first time they participated.