My students had been studying the human body and its systems. We began with the circulatory system and investigated the heart and the purpose of blood. Students had also learned that blood carries certain things that are required by cells, tissue and organs, such as nutrients, hormones, white blood cells and oxygen.

For this science investigation, I integrated a data-collection activity from our Everyday Mathematics curriculum. This allowed students to apply their mathematics knowledge of data collection and data display to our science unit on the human body.

After studying the circulatory system, students understand that the blood transfers oxygen to cells for necessary functions. This investigation shows how the circulatory system is related to the respiratory system. Students are able to apply their understanding of this relationship to actually investigating their own body systems. They are also asked to display their data in two different representations.

Students work in groups of two or three. We had a brief discussion about the task to get them thinking about the topic. Recording sheets provided some directions on how they would investigate the question. Each group had a stopwatch and was assigned to either a jump rope or to the stairs. (Other possibilities might include running, doing jumping jacks or engaging in another physical activity.)

Before beginning, students recorded their pulse rates while at rest. After they recorded their pulse rates, they recorded their breathing rate for one minute. (The “timer” keeps track during the same time as the pulse is recorded.) Once students were in their groups, I asked the class to think about how well they were able to record their pulses. Could they record their breathing rate without thinking much about it? If so, then that person might want to be the “runner.” Another person, also good at recording, might want to be the "pulse keeper." The third person could be the timer.

Then students went to their designated activity. One student completes the activity while another times it. Then the “timer” keeps the time for one minute, the “pulse keeper” records the pulse and the "runner/jumper" counts breaths. While students are performing the experiment, I monitor the pulse and breathing rates that they are writing down. If the rates seem to be off (e.g., pulse rate of 25, breathing rate of 5), you might have them show you one of their recording sessions, or ask if you could see someone else’s pulse/breathing rate.

The students can then switch, so that the first student’s breathing rate returns to normal. The second and third students can then complete the activity. Although the breathing rate and pulse may not be recorded at exactly the same time, the results are similar and should not affect the graphing piece of the task.

After recording results in their tables, students should try this experiment at least one more time to ensure their results are accurate. They should then average their results. This might be a good place to break from the first class session.

During the second class, students can create graphs (with titles and keys). The most difficult part of this that I found was the scale of “beats per minute.” Have the students look at all of their information to determine the scale of the graph. By using a full piece of graph paper, divided by increments of five, we found our information could fit. You may prefer to have students do two separate graphs, although then the relationship between the two lines may not be as obvious.

Science

After completing this experiment, I found other examples of similar tasks. One variation was to use two separate graphs for pulse rate and breathing rate. Another was to time at more frequent intervals, from rest to two minutes at 30-second intervals. The experiments did not implicitly relate the two counts together but instead were done to show how one could monitor both pulse and breathing rate.

Movement/Music

Students could select different types/tempos of music and predict how moving to each would affect heart and breathing rates. Most baroque music is very relaxing to listen to. It is often included in stress management programs because it can produce a heart rate of approximately 60 beats/minute in the listener. Students could explore the effects of listening to different music tempos and compare them with or rank them related to “at rest” rates. Students could also collect heart-rate and breathing-rate data during a practice session for different sports or movement activities.

Mathematics

Students can construct line graphs of data for different physical activities for the purpose of comparing and ranking. Students could determine and discuss differences in the “average rates” for the class in terms of using the mean, median or mode.

Health

Students can compare their investigation findings to research related to regular exercise, developing cardiovascular endurance and physical fitness.

Science

Understandings About the Nature of Science (see appendix)

Have all students measure their pulses at rest (in a classroom setting). Finding the pulse rate on the wrist is a bit harder but safer than using the neck. (If students press on both sides of their neck at the same time, they could pass out.) Take some time to teach students how to find their pulses. Explain to them to press lightly with the fingertips (not with their thumbs) on the outer side of the wrist. They can try counting for a full minute and then try a count for 15 seconds, multiplying it by 4, to verify.

Write the class results on the board. Notice that most resting pulse rates can range from 75–100 beats per minute. Athletes tend to have slightly lower rates, due to conditioning. Some students will have a difficult time finding and recording their pulses but may see from the results of their peers that a pulse rate of 20, for example, is impossible! You may suggest that those students either try it again or choose to be the timer in the experiment.

Calculate and write the average pulse rate of the class on the board so that students can refer to it when recording their own data (not to use that information as their data, but to check theirs for accuracy).

While students are working on their hypotheses, elicit information about what they know about both the circulatory and the respiratory systems.

Ask:

• What does each system do for your body?
• How does that relate to exercise? to fitness training?
• What causes you to have a pulse?
• What connection does the blood have to breathing and the heart?
• How can you determine who will be the “pulse keeper” and “time keeper”?
• What titles should be on your table? (You may need to review with the class what a table should look like or refer to a previous experiment in which they made a table with the class.)
• Using your data, can you explain whether or not your hypothesis was correct?
• Look at your graph. What specific information can you find to back up your conclusion?
• What proof do you have that can help you to know answer the question, “Is my breathing rate related to my pulse?”
• What would happen if you stopped exercising? (This may help them think about a rule to connect breathing rate to pulse.) Encourage students again to think of the function of both the respiratory and circulatory systems.