Lab– Analyzing Muscle Fatigue
Background: Skeletal muscles play an integral role in exercise physiology and the overall concept of "fitness." They play a major, and obvious, role in the area of strength. Strength is largely a function of muscle size. However, skeletal muscles play an equally important, but less obvious, role in the area of endurance (or aerobic fitness). Skeletal muscles perform their function by moving by "burning" the chemical energy in glucose in the presence of oxygen. Endurance is largely a measure of the body's ability to effectively utilize the oxygen necessary for this chemical reaction. The skeletal muscles primarily accomplish the work of athletic competition and training. Consequently, those muscles use a large proportion of the body's total oxygen supply to breakdown glucose with the help of oxygen. This process is called aerobic metabolism or aerobic respiration. The skeletal muscles can also utilize glucose without oxygen, in a process called anaerobic metabolism or anaerobic respiration. Anaerobic respiration can produce energy more quickly than aerobic respiration but, overall, the results are much less satisfactory. Skeletal muscles that are well supplied with oxygen exhibit different physiological responses than muscles that are not as well supplied. This produces a condition, called muscle fatigue, which is familiar to all of us as a qualitative phenomenon. In this activity we will investigate it quantitatively.
Objectives: Students will be able to determine their level of muscle fatigue by performing the “tennis ball exercise” using both hands and evaluating their data to determine any change in muscle performance during sustained exercise. They will also compare performance between right and left hand muscles.
Hypothesis: Predict what you think will happen to your ability o squeeze the tennis ball over time. Use an if…then…because statement.
Materials: Tennis ball, stopwatch or second hand on wall clock, paper, colored pencils, ruler
Procedure:
1. Count the number of times you can squeeze a tennis ball in 10 second intervals over 100 seconds. Try to do so as many as you can in each interval. A legal squeeze causes a dent in the ball made by using the heel of the hand. Your partner should record the data as you squeeze the tennis ball in a table similar to the one below. Also be sure to use the same technique throughout the exercise.
2. DO NOT STOP TO REST between 10 second intervals. Your goal is to build up lactic acid in the muscles that you are using.
CAUTION: To prevent injury the procedure should stop when the activity can no longer be completed. (i.e. when the hand cannot dent the ball).
3. Now repeat the procedure for your other hand and record your data.
4. Record visual observations of the test subject. Note any changes that occur during or after the exercise. i.e. Color changes, body positional changes, noticeable blood vessels, etc…
5. By interview determine the point where the test subject(s) started to feel fatigue (signs of fatigue may not be noticeable in the data.)
6. Note the time it took for signs of fatigue to disappear.
7. Construct a line graph of your results. This is continuous data as you are comparing what happens over time.
Data: Copy this table on your lab write up.
Left hand trial #(10 second intervals) / Number of contractions / Right hand
trial #
(10 second intervals) / Number of contractions / Visual observations
1 / 1
2 / 2
3 / 3
4 / 4
5 / 5
6 / 6
7 / 7
8 / 8
9 / 9
10 / 10
Total: / Total:
Average: / Average:
Questions:
1. Look at the graph for your dominant hand. Compare the number of contractions in trial #1 to the number in trial #10. Explain any differences that you observe.
2. Again look at the graph for your dominant hand. Compare the number of contractions between all ten trials. Explain any differences that you observe.
3. What do the lines on the graph tell you about the functioning of the muscle during intense, repeated exercise?
4. Add up the number of contractions over the ten trials for each hand and record the total in the data table. Then calculate the average number of contractions for each hand and record the average in the data table. Compare the total and average numbers between your two hands. Account for the differences that you observed between your right and left hand.
5. Explain why the body must use anaerobic respiration (lactic acid fermentation) instead of cellular respiration during intense physical activity.
6. What is muscle fatigue and what causes it?
7. Explain why the body requires a period of rest after intense or prolonged physical activity.
Conclusion: Summarize your findings and re-visit your hypothesis.