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Marathon Challenge

Classroom Activity

Learning Objective | Materials | Background | Procedure | Activity Answer | Links & Books | Standards  Print this Teacher's Guide (PDF, 9 pages)

Activity Summary
Students take each other's pulses at rest and after exercise to determine recovery times.

Learning Objectives
Students will be able to:

• measure pulse rate and investigate the affect of exercise on pulse rate.

• construct and interpret a graph displaying recovery time.

• same-sized slips of paper, one for each student

• copy of the "Matters of the Heart" student handout
  (PDF or HTML)
• copy of the "Data Sheet" student handout
  (PDF or HTML)
• copy of the "Plotting Your Results" student handout
  (PDF or HTML)
• clock or timer with seconds

Background
Physical fitness can be determined by tests, including those designed to measure heart rate during exercise, the volume of oxygen consumed while exercising at maximum capacity (known as VO₂ max), body fat percentage, muscle fitness, flexibility, and heart recovery rate.

Heart recovery rate is the time it takes for the heart to return to its normal resting beat. A healthy heart will return quickly to its normal beat after exercising. Heart recovery rates can be improved by making lifestyle changes, such as eating a healthy diet, not smoking, and exercising regularly.

Normal resting heart rate values for different ages are:

• newborn infants: 100 to 160 beats per minute

• children 1 to 10 years: 70 to 120 beats per minute

• children over 10 and adults (including seniors): 60 to 100 beats per minute

Athletes can have much lower resting heart rates, as low as 40 to 60 beats per minute.

In this activity, students take each other's pulses at rest and after exercise to determine recovery times.

1. Begin by asking students the question: "What does heart rate have to do with fitness?" (Students may suggest that a slower heart rate would indicate that the heart is more efficient and has to work less to pump blood.)

2. Organize students into pairs and distribute the student handouts to each student. Review the activity with students.

3. Have students take their resting pulse rates. It is very important that students master the technique of taking their pulse and obtain consistent values before doing the exercises. A slight variation is expected in pulse rate but readings should be within three to five beats per minute during the resting rate calculation. (If taking the pulse for 15 seconds is not generating consistent results, have students take 30-second readings and multiply their values by two.) If students still have problems, you may want to show them how to measure the pulse at the carotid artery in the neck. Whatever method students choose, they should use that method for the entire experiment.

4. Have students average the three resting rate trials and multiply the average by four to determine resting heart rate per minute. Pass out small slips of paper. Have students write their average resting heart rate per minute on their slip and hand it back in. Write the heart rates on the board (without identifying the students) and ask students what might cause any variability in resting heart rates. (Resting heart rates vary with age, sex, physical shape, and cardiovascular condition. Resting rates can also vary due to emotional changes, caffeine intake, and medication side effects. Athletes generally have lower resting pulse rates than non-athletes.) As a class, analyze the data set for high, low, average, and median values. (You may want to have students collect data from a similar number of adults for comparison.)

5. Before each team does its jumping jacks, emphasize to students that when they collect heart-rate data it is important that they collect their data at exactly one-minute intervals after the initial pulse measurement (0) is taken at the moment the jumping jacks are done. Explain to students that each minute includes the time that they are counting the heartbeats.

6. Instruct each team to conduct the exercise and pulse-measuring portion of the activity. If students are having difficulty measuring a pulse rate, suggest that they find the pulse a few seconds before they have to start counting.

7. As a class, determine the range for the y-axis of the "Recovery Time" graph. The range should include the highest heart rate per minute among students as well as the lowest heart rate per minute (including resting heart rates, which will also be plotted). All students should use the same range when plotting their results.

8. Have students do the exercise and plot their results. Collect the graphing sheets and choose a few of the slopes from the "Recovery Time" graph (including the highest and lowest) to plot on the board to show the range of results among class members. Discuss with students what the different slopes mean and how recovery rate is connected to fitness. To conclude, discuss what ways recovery rates could be improved.

9. To illustrate other ways to evaluate fitness, show students the portion of the program at right (3:55) that presents how doctors measure body composition and maximum oxygen consumption (VO₂ max) and animates how the body consumes oxygen.

   After students have viewed the video, ask them to explain how someone with an ideal body weight can still be considered unfit. (Weight is only one measure of fitness. A person with an ideal body weight may still have a poor lean-to-fat ratio. While fat is necessary for body metabolism, more than 25 percent fat in men and more than 30 percent in women is considered unhealthful.)

10. As an extension, have students test for muscle fatigue. Have students open and close a clothespin for 20 seconds. Then have them rest for a few seconds and do another 20-second-long set. How long does it take before muscle fatigue sets in? Have students research and write a one-page report on what causes muscle fatigue.

Safety Note
Students with heart or respiratory conditions should not do the exercises.

During the recovery period, the heart is pumping blood to the muscles. Oxygen and carbon dioxide are being exchanged in the lungs and the muscles. Immediately after exercise, a high demand is placed on the cardiovascular system to provide oxygen and remove carbon dioxide from the muscles being exercised. The pulse rate should be highest right after exercise. As time progresses, more and more blood will be pumped to the muscles exchanging oxygen and carbon dioxide. Over time, the levels of oxygen in the muscle will return to normal and the CO₂ formed during exercise will be removed. At this point, a normal resting pulse rate will return.

A rough estimation of the physical fitness of an individual can be made based on the amount of time required to return to a resting pulse rate. An athlete with an efficient cardiovascular system will return to resting rate in a shorter period of time that someone whose heart muscle and pumping volume are inefficient.

Student Handout Questions

1. What are some of the factors that influence resting pulse rate? Why might an athlete have a lower pulse rate than a person who does not exercise regularly? A variety of factors can influence pulse rate, including physical condition, age, weight, heart disease, medications, smoking, and emotional state such as stress. In general, pulse rates will be lower in those who exercise and are in good physical condition. (Exercise increases the strength of the heart muscle. A stronger heart muscle pumps more efficiently, i.e., more blood pumped per pulse beat. As a result, the number of beats [pulses] required to move the same amount of blood through the body is decreased. In addition, exercise increases the number of capillaries in muscle. This provides more channels to transport oxygen and carbon dioxide during exercise. The result is that gas exchange in both the lungs and the muscles is faster. This, in turn, reduces demand on the heart to pump faster.) Weight also influences pulse rate. The heart must pump harder to move the blood through more body tissue, in this case mostly fatty tissue. This extra tissue places a demand on the circulatory system for oxygen and nutrients. To compensate the heart must pump faster increasing the pulse rate. Additionally, the amount of blood in the arteries increases, often leading to higher blood pressure.

2. In the "Recovery Time" graph, describe the changes that occurred to your heartbeat in minutes 1–7. Use specific numbers from the data table in your response. Answers will vary.

3. If you compared the graph of an extremely fit athlete with the graph of a sedentary 50-year-old individual, would you expect them to be alike or different? Explain your reasoning. You would expect the extremely fit athlete to return to resting heart rate more quickly, as indicated by a steep slope on the graph. This would likely be due to the athlete having a stronger cardiovascular system.

4. What effect could a longer pulse recovery period have on a person's ability to perform certain activities? What effect could a shorter pulse recovery period have? A longer pulse recovery time would limit the type of endurance activity a person could undertake. Endurance events, such as a marathon, provide a continual demand on the cardiovascular system. If oxygen levels are not replaced and carbon dioxide is not removed in muscles, the muscle cells will move into anaerobic respiration, an inefficient state that eventually leads to cramping and muscle fatigue. A shorter pulse recovery time indicates an efficient cardiovascular system. Gas exchange between lungs and muscles is efficient and therefore muscles can function for an extended period of time without moving into anaerobic respiration. This person likely will not become cramped or fatigued as quickly and will be able endure more prolonged exercise.

5. What might a person do to improve his or her recovery period? A person could exercise, which would strengthen the heart muscle, increase its efficiency, increase elasticity in blood vessels, and increase capillary supply to muscles.

Web Sites

NOVA—Marathon Challenge
www.pbs.org/nova/marathon/
Features profiles of Team NOVA members, four of the runners' diaries, a training calendar, information about how exercise affects the body, tips for rookie runners, and more.

Amazing Heart Facts
www.pbs.org/nova/heart/heartfacts.html
Gives facts on heart rate and the structure of the heart.

Map of the Human Heart
www.pbs.org/nova/heart/heartmap.html
Shows blood flow through the heart and diagrams heart structures.

Researchers Find Heart Rate Worth a Thousand Words
www.webmd.com/news/20000919/researchers-find-heart-rate-worth-thousand-words
Explains heart rate recovery and how it can be improved.

Books

Essentials of Human Anatomy and Physiology
by Elaine Nicpon Marieb. Redwood City, Calif.: Benjamin Cummings Publishing Inc., 1994.
Provides basic chemistry of the human body and an overview of all its systems.

The Human Body: An Illustrated Guide to Its Structure, Function, and Disorders
by Charles B. Clayman, MD. London, New York: DK Publishing, 1995.
Uses medical drawings and images from diagnostic technologies to help explain the body's anatomy, function, and common disorders.

The "Matters of the Heart" activity aligns with the following National Science Education Standards (see books.nap.edu/html/nses).

Grades 5-8
Science in Personal and Social Perspectives
Personal health

Grades 9-12
Science in Personal and Social Perspectives
Understanding personal and community health

Classroom Activity Author

Fred Sculco taught science for 35 years, including courses in biology, environmental science, genetic engineering, and alternative energy resources. In addition to his middle- and high-school teaching experience, Sculco has worked as a consultant for the National Institutes of Health, the U.S. Department of Energy, and the Massachusetts Audubon Society.