Name_____________________________________________ Date_____________________ Period: _______________
Investigating Muscle Fatigue Lab
Background Information
Normally, muscles use oxygen through a process known as cellular/aerobic respiration to make
energy (or ATP) from sugar (glucose). This process is very efficient and produces 36 ATPs for each molecule
of glucose. Carbon dioxide and water are the results of the reaction. When muscles undergo rigorous
exercise they require more oxygen to make ATP than the blood can supply. At this point the muscle is forced
to produce ATP without oxygen. This is known as anaerobic respiration. Anaerobic respiration only
produces 2 ATP for each molecule of glucose.
The advantages of anaerobic respiration are that the muscle cell can make ATP without oxygen
and it can make ATP very quickly. This is a particular advantage when lifting heavy objects. The big
disadvantage to anaerobic respiration is that it produces lactic acid which gives muscles a temporary burning
sensation.
Muscle fatigue (or tiredness) results when the demand for ATP is greater than the rate at which
ATP can be produced in the muscle fibers. As a result, ATP levels are too low for muscle fibers to produce
their maximum force contraction. Under conditions of extreme fatigue, muscles become incapable of
contracting or relaxing. (They stop working.)
Today you will experience the use of anaerobic and aerobic respiration by the muscle fibers in
your fingers. You will experience the production of lactic acid and the sensation it produces in your muscles.
The lab will demonstrate how your body used the resources avail be to provide you with the energy you need
to do work.
Complete the following chart:
Aerobic Respiration
Anaerobic Respiration
Procedure
1. You will work in groups of two to complete this activity. One person will squeeze the clothespin and count
the number of times they squeeze it in the given amount of time. The other person will be the timer and
recorder (record squeezer’s data in squeezer’s data table!).
2. The person squeezing the clothespin should hold the clothespin in the thumb and index finger of the
dominant hand (right hand if person is right handed), and open and close it while the other fingers of the
hand are held out straight. The number of times the clothespin opens to its maximum distance in 20
seconds will be recorded by the second person.
3. You should try to squeeze quickly and completely, to get the maximum number of squeezes for each trial.
4. Repeat this process for nine more trials, 20 seconds each trial, and record your results. Do not rest the
fingers between trials.
5. Repeat steps 2-4 for the non-dominant hand. All data should be recorded in the table below.
6. Repeats steps 2-5 for the other person (squeezer now becomes timer and recorder).
7. Create a double line graph of the data.
Data
Trial
# of squeezes in 20 seconds
Dominant Hand
# of squeezes in 20 seconds
Non-dominant hand
1
2
3
4
5
6
7
8
9
10
Conclusion
1. What happened to your ‘strength’ as you progressed through each trial? How does your graph show this?
2. Describe how your hand and fingers felt during the end of your trials.
3. What product of anaerobic respiration caused the feeling you described in question 2?
4. Were your results different for the dominant and the non-dominant hand? Explain why they would be
different.
5. Your muscles would probably recover enough after 10 minutes to operate at the original efficiency. Explain
why.
6. Explain why anaerobic respiration causes your cells to be less efficient.