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Name: _____________________________ Date: _____________ Group: ________________________
Muscular System
Clothespin Lab / Muscle Fatigue
Purpose:
What are the effects of anaerobic respiration on your muscles?
Background:
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 38 ATPs for each
molecule of glucose. Carbon dioxide and water are the results of this 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 produces only 2 ATPs for each molecule of glucose. The
result of this reaction is lactic acid.
The advantages of anaerobic respiration are that the muscle cell can make ATP without oxygen
and it can make ATP very quickly. This 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 condition of extreme fatigue, muscles become
incapable of contracting or relaxing. (They stop working)
Today you will experience the use of aerobic respiration and anaerobic respiration by the
muscle fibers in your fingers. You will experience the production of lactic acid and the sensation it
produces in you muscles. The lab will demonstrate how your body used the resources available to
provide you with the energy you need to do work.
Vocabulary:
Aerobic Respiration- A form of cellular respiration that requires oxygen in order to generate energy.
(38 ATP/1 glucose)
Glucose- Sugar energy source.
ATP- Energy
Anaerobic Respiration- The production of energy without oxygen. (2 ATP/1 glucose)
Muscle Fatigue- The temporary failure of muscle strength, power, and endurance. The muscles cannot
contract or work properly.
Lactic Acid- Produced from anaerobic respiration, gives the muscles a burning sensation.
Name: _____________________________ Date: _____________ Group: ________________________
Hypothesis:
If __________________________________________________________________________________
Then _______________________________________________________________________________
Because_____________________________________________________________________________
____________________________________________________________________________________
Materials: 1 clothespin, 1 timer, 1 pencil, 1 data table, 1 sheet of graph paper
Procedure 1) Hold the clothespin straight out and in between the thumb and forefinger of your non-writing
hand. The rest of your fingers should be closed like a fist.
2) We will be doing five (40 second) trials with a 5 second break between trials.
3) When the teacher says “Go”, start squeezing the clothespin as many times as possible within the
thirty second interval.
4) Keep a count of the number of times you have closed the clothespin and write the number down
in the data table.
5) Graph the data that was just collected. Label the x-axis with the trial number, and the y-axis with
the number of squeezes.
Data Table:
Trial
# of Squeezes
1
2
3
4
5
Results and Analysis:
Using graph paper draw a graph showing how your # of squeezes changed over time.
Use a line graph when graphing change over time.
Name: _____________________________ Date: _____________ Group: ________________________
Conclusion: Answer the following questions.
1. Fill in the following chart:
Aerobic
Anaerobic
Require Oxygen?
# ATP per glucose
Byproducts
2. What happened to the number of squeezes as you conducted this experiment? _______________
______________________________________________________________________________
3. Did your muscles experience any muscle fatigue? ____________________________________
4. How did your breathing rate change? ______________________________________________
5. Did you feel your muscles start to “burn” at any point during the experiment? If so, when?
____________________________________________________________________
6. What material causes this burning sensation in muscles? _______________________________
7. Did your muscles have to work without oxygen at all during the trials? ______________________
8. How do you know? _______________________________________________________________
_______________________________________________________________________________
9. What is it called if muscles have to make energy (ATP) without oxygen? _____________________
10. Which trial had the most aerobic respiration? ________________________________________
11. How do you know? ____________________________________________________________
_____________________________________________________________________________
12. Which trial had the most anaerobic respiration? ______________________________________
13. How do you know? ____________________________________________________________
_____________________________________________________________________________
14. True or false: ATP is our body’s energy. _____________
15. True or false: ATP is made from glucose. _____________
16. True or false: Muscles can’t work without oxygen. _____________
17. True or false: ATP use causes a burning sensation in muscles. _____________
18. True or false: A lack of ATP causes muscle fatigue. _____________
19. True or false: Anaerobic respiration is more efficient then aerobic respiration. _____________
20. True or false: Aerobic respiration results in the formation of oxygen and water. _____________
Name: _____________________________ Date: _____________ Group: ________________________