BioEd Online

Teacher Background

Every day, it seems we hear or read about the importance of exercise for heart health. Why? What is the relationship among the heart, circulation, and exercise? The Children’s Museum of Houston’s PowerPlay exhibit is designed to teach young people about heart health and reinforce healthy behaviors, as students discover new ways to be physically active. While they progress through the exhibit, students will be able to track heart rate, measure strength, and examine performance levels. This activity will enable students to learn how their hearts respond to physical activity. It should be completed before they visit the Museum.

Even when you are sleeping, reading, or watching TV, your body uses oxygen and nutrients, and produces carbon dioxide and other wastes. When you get up and start moving around, your body demands more oxygen and produces more carbon dioxide as waste. These demands increase even further if you start running or doing another strenuous activity. The circulatory system responds by raising the heart rate (how often the pump contracts) and stroke volume (the amount of blood pumped with each contraction) to increase the cardiac output (the volume of blood pumped from the left ventricle per minute). During exercise, heart rate can rise dramatically, from a resting rate of 60–80 beats per minute to a maximum rate of about 200 for a young adult.

A pumping heart makes the sound we call the “heartbeat.” The “lub-dub” of a heartbeat is actually the sound of blood being pushed against the closed, one-way valves of the heart. One set of valves (tricuspid and bicuspid) closes as the ventricles contract. This generates the “lub” of our heartbeat. A second set of valves (pulmonary and aortic) closes when pressure in the ventricles is lower than the pressure in the aorta and pulmonary artery. This produces the “dub” of our heartbeat.

As the heart beats, it forces blood from the ventricles into the muscular, elastic walls of the arteries, causing them to expand. Each artery wall then contracts to “push” the blood onward, further through the body. You can feel those “pulses” of blood, moving through the arteries in rhythm with your heartbeat. The number of pulses per minute, usually referred to as pulse rate, is measured in beats per minute (BPM). The average pulse rate for a child ranges from 60 to 120 BPM.

Objectives and Standards

Texas Essential Knowledge and Skills (TEKS) Objectives

Science

3.2.A-F; 4.2.A-F; 5.2.A-F

• Student uses scientific inquiry methods during laboratory and outdoor investigations.

3.4.A-B; 4.4.A-B; 5.4.A-B

• Students know how to use a variety of tools, materials, equipment, and models to conduct science inquiry.

3.2.E; 4.2.E; 5.2.E

• Students demonstrate that repeated investigations may increase the reliability of results.

Health

3.1.A; 4.1.F; 5.1.E

• Students will recognize and explain ways to enhance and maintain health.

4.2.B; 5.2.A

• The student recognizes the basic structures and functions of the human body and how they relate to personal health throughout their lifespan by describing the basic functions of the major body systems such as the circulatory system.

Materials and Setup

Materials per Class

• Stopwatch with second hand, watches with second hand, or classroom clock

• CD player or other music player

• One music selection without words that has a strong, up-tempo beat

• One music selection without words that is slow and relaxing

Materials per Student

• Access to a clock or watch with a second hand (or one stopwatch per team)

• Copies of “Your Pulse Rate” and “Heart Rate Observations” student sheets

• Optional: Lab notebook

Procedure and Extensions

Time

Two class periods of 45–60 minutes: one to collect data and a second to process, present and interpret measurements

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Engage

1. Ask students if they know how to measure their heart rate. Distribute copies of “Your Pulse Rate” student sheets.

2. Show students how to measure heart rate (beats per minute) by feeling for the surge of blood through an artery in the wrist (not the neck, see "Safety"). Have each student find his or her pulse by placing slight pressure on the wrist with the middle and ring fingers. Tell students not to use the thumb, because it has a pulse of its own (see illustration, PDF).

3. Allow students to practice taking their pulse rates several times while you count off 15-second intervals. Instruct students to multiply the 15-second pulse count by four to determine how many times their hearts beat in one minute.

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Explore

1. Ask students if they think heart rate can vary, or if it always is the same. Ask, What kinds of situations might cause heart rate to change? [exercise, rest, standing, walking up stairs, nervousness, excitement, etc.]

2. Distribute the “Heart Rate Observations” sheets.

3. Review the activity sheet with students, stopping periodically to ask questions and make sure they understand the content.

4. Ask students to complete the prediction section for the first activity listed (i.e., students should check whether they expect their heart rates to increase, decrease or stay the same when they “Listen to soft, slow music”). Explain that predictions should be made in order, and for only one activity at a time. (The outcome of each activity may influence students’ predictions for the next.)

5. Have students sit quietly for one minute. Then, instruct them to count their pulses while you time them for 15 seconds. To establish their resting, or beginning, pulse rates, students should multiply by four the number of pulses they counted in 15 seconds. Have them record their beginning pulse rate numbers on the appropriate lines of their “Heart Rate Observations” sheets.

6. Have the class sit quietly and listen to soft music for one minute. Then, have all students measure and record their pulse rates once again. Continue to lead students, as a class, through the first three activities on the sheet. During the deep breathing exercise, make a point of telling students when to inhale and exhale, to ensure that they maintain a very slow pulse rate. Instruct students to continue this pattern of slow breathing as they take their pulses.

7. Have students complete the remaining activities listed on the sheet, in order (see PDF). Each student may work with a partner, if desired. Remind students to record their pulse rate predictions before each step. Students should apply anything they learned from previous experiences when making each new prediction.

8. Be sure students have sufficient time to regain their resting pulse rates before beginning each new activity. You may wish to have them record how long it takes to return to their resting heart rates. (Pulse rates will recover more quickly if students are seated.) Some students’ heart rates may fall below their resting rates before returning to normal. This is common.

9. Be sensitive to students who may feel uncomfortable doing jumping jacks or sit-ups in front of the class, or those who may have health issues, such as asthma, which may be problematic.

10. Instruct students to complete the written questions below the table on the activity sheet.

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Explain

1. Have students form groups of four. Each group should combine its data, create a presentation of its collective results (graph, table, pictures, etc.), and present its findings to the class.

2. Ask, What have you learned about heart rate? Students should have observed that heart rate increases during more strenuous physical activities.

3. Ask, What happened to your breathing during activities that increased your heart rate? Students should have noticed that breathing rate and volume of air taken in increased when the physical activity became more demanding.

4. Help students to understand the relationship between the body’s need for more oxygen during exercise and the heart’s effort to deliver that oxygen (by pumping blood more quickly).

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Elaborate

1. Ask students, Why would an athlete have a slower resting heart rate than a non-athlete? Discuss the normal resting heart rate for an average adult (72 BPM), compared to the following average resting heart rates in beats per minute.

   • Weightlifter - 65 BPM

   • Football Player - 55 BPM

   • Swimmer - 40 BPM

   • Marathon Runner - 40 BPM

2. Ask, Why would a slower heartbeat during rest indicate a healthier heart? Explain that regular exercise strengthens the heart, and that a well-conditioned heart can pump the same amount of blood with fewer beats. Cardiovascular exercise (such as swimming and running) also increases the size of cardiac muscle cells and the heart chambers, which actually causes the heart to grow larger. Therefore, even with a lower number of beats per minute, a healthy, fit heart pumps more blood than a heart that is not accustomed to exercise.

3. To achieve the best health, we must make exercise a lifestyle, not a temporary fitness “kick.” Studies have found that non-activity for as little as three weeks can reduce heart muscle size and stroke volume (amount of blood pumped from the left ventricle in each contraction).

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Evaluate

To conclude the activity, have students write a journal entry describing what they learned about the connections between activity intensity and heart rate. Students should complete the following statements, and may want to draw pictures to accompany their words.

I discovered...
I learned...
I never knew...
I was surprised...
I enjoyed…

Handouts and Downloads