Effects of Exercise on Heart Rate...

Lesson Overview
In this lesson, students work in small, collaborative groups to measure their heart rate (pulse) at rest, during exercise, and after exercise. Groups then carry out their own investigations of how different activities affect heart rate and breathing rate.


Two 45-minute periods:
        5 minutes for introducing the activity
        30 minutes for Part A (exercise and heart rate)
        10 minutes for discussion
        30 minutes for Part B (exercise and breathing rate)
        15 minutes for discussion

Objectives
  • Measure pulse rate and breathing rate.

  • Recognize that pulse rate is heart rate.

  • Investigate the effects of different types of activities on heart rate and breathing rate.

  • Graph and interpret data from investigations.

Process Skills
Comparing/Contrasting
Controlling Variables
Designing Experiments
Graphing
Interpreting Data
Investigating
Measuring
Observing
Predicting
Questioning

Lesson Background
The circulatory system is a transport system. The heart pumps, and the blood delivers oxygen and nutrients to body cells and carries wastes away through a network of blood vessels.

The heart pumps blood out to the body through the aorta, the largest artery in the body. Like a branching tree, the aorta divides again and again into smaller and smaller arteries, eventually forming tiny blood vessels called capillaries, which carry blood to all the cells in the body. The capillaries connect to larger and larger vessels called veins, which carry blood back to the heart.

Every time the heart beats it sends a surge of blood through the arteries. You can feel this surge, or pulse, along large arteries near the surface of the skin, especially along the neck and the inside of the wrist.

Heart rate can thus be determined by counting pulse rate. An average adult heart beats about 60 to 80 times a minute. During exercise heart rate increases because the heart must beat faster to supply working muscles with more food and oxygen.

Vocabulary (optional)
It's a Fact!
Without blood, your cells would die. Brain cells die after just a few minutes without blood flow.
aerobic activity: activity that increases your muscles' need for oxygen and thus speeds up breathing and heart rate. Aerobic exercise involves using large muscle groups in repetitive activity over an extended period. To supply the muscles with oxygen, the heart beats faster and breathing rate increases. Aerobic activity helps make the heart stronger and increases cardiovascular fitness. Common aerobic activities include running, cycling, swimming, dancing, skating, and walking.
anaerobic activity: activity that does not increase the muscles need for oxygen. Anaerobic exercise, such as weight lifting, can build strength, but does not increase cardiovascular fitness.
arteries: blood vessels that carry blood away from the heart.
capillaries: microscopic blood vessels that carry blood to individual cells.
heart: organ that pumps blood through the body.
heart rate: the rate at which the heart pumps blood.
pulse: the surge of blood felt along certain arteries each time the heart's ventricles contract.
veins: blood vessels that carry blood back to the heart.

Materials
Introducing the Activity
  • two plastic wash basins

  • one plastic cup (about 150-mL capacity)

  • stopwatch or watch with second hand


Activity (per group)
  • none

Advance Preparation
  • Gather and prepare the necessary materials.

Safety
  • Caution students to stop any activity if they feel dizzy or out of breath.

Introducing the Activity
Ask students how fast they think their heart beats when they are sitting still. To demonstrate how hard the heart works every minute, have student volunteers try the following activity:
  • Set two wash basins next to each other on a table. (Be sure to protect the surface from spills.) Fill one wash basin two-thirds of the way with water.

  • Have one student use a stopwatch or clock with a second hand to time one minute.

  • Give the other student a plastic cup that holds about 150 mL (about the amount of blood an adult heart pumps with each beat).

  • Challenge the student to use the cup to try to move the water from one basin to the other as fast as the heart pumps. To pump as fast as an average adult heart, the student would have to move 70 cupfuls in one minute.


Activity
Procedure
Part A
1 Demonstrate for students how to take a pulse at the wrist (radial artery) and at the neck (carotid artery). To find a pulse rate: Place the index and middle fingers on your wrist or your neck. (Don't use your thumb. It has it's own strong pulse.) Hold your fingers there until you feel the steady beat of your pulse. (You may have to move your fingers around a little until you find the strongest pulse. Don't press too hard.)

2 Help students find their own pulses at these two places. Ask students what the pulse rate measures. Explain that with each heartbeat, the heart sends a wave of blood surging through the blood vessels known as arteries. You can feel this surge of blood most easily at places where arteries are near the surface of the skin, such as at the inside of the wrist or the side of the neck. By measuring pulse rate we are actually measuring heart rate.

3 Have all students measure their pulse rate while seated quietly at their desks. Explain that this is a resting pulse rate. Students can determine their pulse rate by counting the pulses in 15 seconds and multiplying that number by 4 (to get heartbeats per minute). Have students find their pulses, then give a signal and have students count the pulses, while you time 15 seconds.

4 Ask students: What do you think happens to your heart rate when you run? Why? Record students' hypotheses on the board.

5 Then have students jog in place for 1 minute. At the end of that time, have them determine their heart rates as they did before.

6 Have students compare their resting and active heart rates. Collect class data in a chart on the board. Plot the data on a bar graph. Have students look for patterns in the data.

7 Let students work in small groups to investigate the effect of an activity on heart rate. Students might choose an activity such as stair climbing, lap running, raising and lowering an arm, doing a headstand, or playing a board game. Each activity should be carried out for the same amount of time, so that groups can compare data.

8 Have the class discuss options and agree on the amount of time and general procedures for collecting data. For example, students might decide to take the participant's pulse before the activity, during the activity, at the end of the activity, and 5 minutes later.

9 Help students determine the specific procedures for their investigations. You may want to discuss how to control variables and how to test just one variable at a time. You may also want to give students a sample data table.

10 Have students graph their data and share the results of their investigations. Have students look for patterns in the data reported. You might want to introduce the terms aerobic and anaerobic and have students draw conclusions about the effect of each type of activity on heart rate and the importance of aerobic activity in strengthening the heart.



Part B
1 Ask students: How do you think exercise affects your breathing rate? Why?

2 Help students design investigations into the effects of different types of activities on breathing rate.

3 Let students share the results of their investigations and look for connections with the data they collected earlier on exercise and heart rate.


Extensions
  • Have students find out the average heart rates for different animals and graph them on a bar graph to compare with students' average heart rates.

  • Have students design an investigation and collect data on how long it takes their heart rate to return to its normal, resting rate after exercise. (In general, the fitter you are, the faster your heart rate returns to normal because a fitter heart is more efficient at pumping blood.)

  • Have students calculate how many times their heart beats (or their lungs inhale and exhale) in one hour, one day, and one year.
Assessment
Have students summarize the results of class investigations in a news article.

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