#### Objective

Students will measure their pulse rate and explore how heart rate is affected by various activities.

## Pulse of Life

### Key Questions

• How does your heart rate change after exercise?
• What can change your heart rate besides exercise?

### Materials

#### For every group of four students

• clock or watch with a second hand or a digital reading

### Procedure

1. Help the students locate their pulse points either on their wrists or necks. Ask students to place their right index and middle finger on the palm side of their left wrist. On the neck, the pulse point is located beneath the ear and jawbone. How do I find my pulse?
2. Count the number of beats in 15 seconds. Multiply this by four (15x4=60, there are 60 seconds in one minute). This is how many times the heart beats in one minute. Have students enter this "at rest" heart rate on their chart. (Student pulse rate at rest will vary between 60 - 110 beats per minute. Adult rates are lower.)
3. Do some exercise such as running in place, jumping jacks, or other exercise for one minute. Stop and calculate pulse again over 15 seconds. Calculate the heart rate for each activity and show this on the graph.

### Extensions

1. Compare the heart rates of students in the class. Are the heart rates the same or different?
2. What is the average heart rate of all the students? The average heart rate can be found by adding up the column of numbers of all the heart rates listed and dividing this number by the total number of students.
3. Have the students collect pulse rates from various adults and list this on another graph. Calculate the average heart rate for adults. How does this compare with the students' average heart rate?
4. Have students keep a record of their heart rates for one week by taking their pulse a few times a day. Note time of day and activity at the time.
5. The amount of time the heart takes to return to a normal at-rest rate after exercise is called recovery time. This is a measure of the body's general fitness. The shorter the recovery time, the higher the level of fitness. Determine recovery rate by first measuring and recording the pulse rate at rest. Next, run in place for two minutes. Now measure the pulse rate every minute until the at-rest rate is reached. How long did it take the heart to return to the normal rate?

### Notes to the teacher: Pulse Rates

During each heartbeat, the muscles of the heart contract causing a wave of pressure which forces blood through the arteries. This wave of pressure is known as a pulse. There is one pulsation for each heartbeat. The pulse can be felt at various points on the body where the arteries are just under the skin, such as the temples, neck, crook of the elbow, wrist, groin, back of the knee, and the inside back of the ankle. The normal pulse rate varies with age. Below is a chart listing the range of heart rates and average heart rate for various ages.

With exercise or physical activity, the heart rate increases to supply the muscles with more oxygen to produce extra energy. The heart can beat up to 200 times per minute with extreme exercise. The brain sends nerve signals to the heart to control the rate. The body also produces chemical hormones, such as adrenaline, which can change the heart rate. When we are excited, scared, or anxious our heart gets a signal to beat faster. During a fever, the heart beats faster to bring more blood to the surface of the body to release heat and cool the body. The heart rate increases during and after a meal to send more blood to the digestive system. A trained athlete's heart can pump more blood with each beat so his or her heart rate is slower. Likewise, an athlete's recovery time is shorter.

There are two ways the heart can meet the body's need for oxygen during exercise. It can beat faster or it can beat harder, moving more blood per pump. But it can only beat harder if it has been strengthened through regular exercise.

Range of Heart Rates per Minute and Average Heart Rate for Various Ages

 Age Range Average Rate 0-1 month 100-180 2-3 months 110-180 4-12 months 80-180 1-3 years 80-160 (130) 4-5 years 80-120 (100) 6-8 years 70-115 (100) 9-11 years 60-110 (88) 12-16 years 60-110 (80) >16 years 50-90 (70)

#### Vital Signs

http://sln.fi.edu/biosci/monitor/vitals.html
The Franklin Institute's extensive website includes some brief but informative information about the pulse and blood pressure, and average rates for both.

#### BodyQuest

http://library.thinkquest.org/10348/
BodyQuest was designed in the Science and Mathematics category for ThinkQuest '97, and is aptly described by its creators as, "an exploration of anatomy designed for students aged between 11 and 16." If you're looking for a short explanation of the circulatory system and a few visual components, this is the place.

##### | heart | lungs | videos | lessons | tools | about | contact |

Visiting the Science Museum of Minnesota?
Learn about the Human Body Gallery.