Muscles At Work
An activity from the Burroughs Wellcome Student Research Program The Science of Sports

Problem:

From experience you know that exercising causes your heart rate to go up and your body temperature to rise. What is the realtionship between heart rate and muscle temperature during exercise?

Introduction:

When you exercise, your muscles use oxygen and stored chemical energy to contract and expand. The oxygen is supplied by blood which is circulated by the heart. The chemical energy is stored directly in the muscle cells, but 60% of that energy is converted to heat. Therefore, exercising causes a change in heart rate and muscle temperature.

Materials

ULI and Data Logger software
OR
LabPro and LoggerPro software

Heart Rate Monitor
Temperature Probe
3 -5 pound weights

Procedure:

ULI: For this activity you must work with a partner. Plug the temperature probe and heart monitor into the ULI and open the Data Logger program on your computer. Under the File menu choose Open. Choose the file Standard Temperature Probe in the Temperature Probe file under Experiment Files. Load the calibration. Both temperature and heart rate will be displayed on the same graph. Under Axes in the Display menu change the x-axis maximum to 180 seconds.

LabPro: For this activity you must work with a partner. Plug the temperature probe and heart monitor into the LabPro and open the LoggerPro program on your computer. Under the Experiment menu choose Show Sensors. Choose sensors you have plugged in the appropriate channels. There should be 2 graphs, one for each probe. Change the x-axis maximum to 180 seconds for both graphs.

Exploring:

Place the tip of the temperature probe against the muscle that is to be exercised (biceps, triceps, quadraceps etc.) for at least one minute to allow the probe to stabalize at the muscle's temperature. Once the temperature has stabalized, clip the heart rate monitor to the ear lobe or to the fleshy part of the hand between the thumb and forefinger. This monitor will record the heart rate during the activity.

Be completely still (no talking!). Another student should click Start. At the end of thirty seconds begin exercising. Exercise steadily with the weight for two minutes.

Select the graph, then select the Display menu ( DataLogger) or Analyze menu (LoggerPro) and choose Auto Scale. To determine the minimum and maximum temperatures, select Analyze and choose Statistics. Record the minimum and maximum temperatures.

Look at the heart rate data and select the first 6 second interval to enlarge for counting. Place the pointer at 180 on the x-axis and click. When the box is highlighted, type in 6, then click on the graph. The beats should now be spread out to be counted easily. Count the beats in the interval and multiply by 10 for beats per minute. Record the initial and final hear rates. If you have difficulty counting the first 6 seconds, try the next series.

Repeat the activity with a second student using the same muscles. Then have each partner perform the activity again using a different set of muscles.

Data Table

Trial	Muscle	Minimum Muscle Temperature	Maximum Muscle Temperature	Change in Temperature	Initial Heart Rate	Final Heart Rate	Change in Heart Rate
1	.	.	.	.	.	.	.
2	.	.	.	.	.	.	.
3	.	.	.	.	.	.	.
4	.	.	.	.	.	.	.

Discussion:

• Why is the change in muscle temperature an expected event? What is occuring to cause this change?
  
  
• Why is the change in heart rate an expected event? What is occuring to cause this change?
  
  
• What other body processes are also changed by exercise?
  
  
• Did all the students in the group or class record similar results? What do you think accounts for differences among student data?
  

Conclusion

What is the relationship between heart rate and muscle temperature? Use your data to make a graph to show this relationship.