Examine your heart rate
I find that exploring science as you learn about yourself is fun. With this activity, you will examine the rate the heart pumps blood through your body by measuring your pulse.
Your heart rate, or pulse, is the number of times your heart beats per minute. 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, back of the knee, and the inside back of the ankle. I find it is easiest to find a pulse on my wrist or neck.
Heart rate varies with age, air temperature, body position, body size, emotions, and physical activity. When you exercise, your heart rate increases to supply the muscles with more oxygen to produce extra energy. The brain sends nerve signals to the heart to control the rate. The body also produces chemical hormones, 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. 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.
Let’s explore heart rate and how it changes during different activities!
What you will need:
Stopwatch or clock/app that counts seconds
A place to sit and a place to do physical activity
Paper and something to write with
Optional: graph paper for extensions on this activity
Find your pulse or heart rate by placing two fingers between the bone and the tendon over your artery — which is located on the thumb side of your wrist. Or, place two fingers on the side of your neck under your jawbone. Move your fingers around slowly until you feel your pulse.
Sit quietly and count the number of beats or pulses in 15 seconds. Record the number on your sheet of paper. This is your heart per 15 seconds. To calculate beats per minute, multiply this number by 4.
beats/15 seconds resting X 4 = beats/minute resting heart rate
This is your resting heart rate.
Now, do something active to see how this changes your heart rate. Try doing jumping jacks, push-ups, or sit-ups for 1 minute. Then sit down, find your pulse again, and count the number of beats or pulses in 15 seconds. Record the number on your sheet and calculate active beats per minute by multiplying the number by 4.
beats/15 seconds active X 4 = beats/minute active heart rate
Compare the two numbers.
Are they different? If so, did your heart rate go up or down after activity? If not, why not?
What does this make you curious about? If your family members did the same activity, what do you think their heart rates would be? How do different activities affect your heart rate?
Do you need some background information or resources? Here are a few I like to use:
Normal heart rates from Mayo Clinic
All about heart rate from the American Heart Association
An interactive tool for your target heart rate from HealthPartners
There are many things you can explore related to heart rates. Here are some suggestions to get you started:
Compare the heart rates of people in your family, both resting and active. Are the heart rates the same or different? Make a bar graph to show your results.
Scientists often repeat experiments to ensure accuracy. You could repeat the measurements 3 times and average your results. Does this change your outcome?
Keep a record of your heart rates for one week by taking your pulse a few times a day. Note the time of day and activity at the time. Graph the results to see if you notice a trend.
What other variables can you study that changes your heart rate? Graph the changes.
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 the 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?
Look at different activities and the relationship to heart rate by following this activity created by the American Heart Association.
Run your own experiments to answer the questions you have about heart rate. Record and track the data.
Whatever you learn in the process, please share your results with other Science Museum of Minnesota fans using the hashtag: #ShareYourDiscovery