Aerobic Or Anaerobic: Can You Tell When the Switch Occurs?

PROBEWARE INVESTIGATION 3  A

Aerobic or Anaerobic: Can You Tell When the Switch Occurs?

NOTE: A physical education teacher should be available to the teacher and class during this investigation. No individual should be allowed to use the treadmill until he or she can demonstrate the ability to do so
correctly and safely.

In most day-to-day activities, muscles burn stored energy by using oxygen as the final acceptor of electrons. This is known as aerobic respiration. However, if muscles require more energy than can be supplied by the aerobic system, another system helps out. This anaerobic system produces energy needed by muscles during a period of high exertion and requires no oxygen. However, the byproduct of anaerobic activity is lactic acid buildup. This is the common burning sensation felt in the legs or arms when worked to exhaustion. The lactic acid is “poison” to the muscle, and with high levels muscular action stops. The heart rate at which this anaerobic system starts is generally referred to as the anaerobic threshold. This happens when the heart is beating at around 80% of its maximum. One method to estimate a person’s anaerobic threshold is to subtract the age of the subject from 220, and then multiply that value by 0.8. For example, for an 18 year old, his/her anaerobic threshold would be (220 - 18) x 0.8 = 162 beats per minute. Knowing the point at which your anaerobic system will take over is important if you are training for low intensity versus high intensity events.

In this investigation, you will calculate your personal anaerobic threshold heart rate value. Then you will attempt to estimate when you have reached this heart rate value while exercising and will compare your estimate with the actual calculated value.

Problem

How accurately can you estimate your anaerobic threshold while exercising?

Prediction

Calculate your anaerobic threshold as outlined above:

220 – your age x 0.8 = ______
beats per minute

Predict how close you will come to guessing your anaerobic threshold while exercising:

Number of beats away = ______

CAUTION

This investigation involves strenuous exercise for the subjects. Be sure that these individuals are in good health and are somewhat fit before attempting this investigation.
Ensure that all individuals are familiar with the operation of the treadmill being used in order to minimize risk of injury by improper use of the machinery.

Materials

computer system and interface
heart rate sensor
treadmill

Procedure

1.Copy the table below.

2.Set up the computer and attach the heart rate sensor to the subject. The experiment clock should be set to 15min and the computer screen should display both the latest heart rate and a graph depicting the heart rate changes over the 10min.

3.Start the treadmill at an intensity that is deemed very easy by the subject and begin collecting data. The first 3min serve as the warm-up period.

PROBEWARE INVESTIGATION 3  A

Aerobic or Anaerobic: Can You Tell When the Switch Occurs? (continued)

4.After 3min have passed, allow the subject to increase the intensity of the treadmill gradually every minute.

5.Instruct the subject to tell you when he/she feels he/she has reached 80% of his/her maximum heart rate or anaerobic threshold.

6.When the subject has given you the sign, stop recording data and slow down the treadmill gradually.

7.Compare the heart rate value showing when the data recording ceased with that of the subject’s calculated anaerobic threshold and

find the difference in the values. Input the information into the table below. Be sure to track whether the subject was over or under the calculated AT value by inserting a plus or minus sign in front of the difference value.

8.Repeat steps 2–7 for all subjects, recording the data in your table.

9.Generate a graph showing each subject in the experiment along the x-axis, and the number of beats over or under the calculated AT value along the y-axis. See if any trends exist.

Observations

Subject / Calculated AT Value (bpm) / Estimated Heart Rate Value (bpm) / Difference (bpm)
1.
2.
3.
etc.

Post-lab Questions

1.Which subject had the least difference between calculated and estimated heart rate value? What was the difference?

2.Which subject had the largest difference between calculated and estimated heart rate value? What was the difference?

3.Why was the subject given a warm-up
period of 3 min?

Conclude and Apply

4.What can you conclude about the graph you have created? Do any trends exist?

5.If given the chance to complete the study again, do you think the estimated values of the subjects would be closer to their actual calculated values? Explain.

Exploring Further

6.Using the Internet, research different methods used by athletic trainers to increase the anaerobic threshold of their trainees.