Muscle Fatigue Lab
- The Biology Buzz Place
- 2 days ago
- 6 min read
In this lab students will observe how muscle fatigue affects the amount of work muscles can do. Students will make predictions on how intense exercise affects how much work their muscles can handle without a break. When skeletal muscles contract and relax (shorten and lengthen), they cause bones to move. This is work, and all work the body does requires ATP, which is the energy currency in our bodies. ATP is produced through the process of cellular respiration. Muscles use up their oxygen and ATP supply during activities that are continuous, for example, like sprinting and lifting a 5lb barbell.
When oxygen and ATP stores are depleted, muscles can no longer contract, and lactic acid waste accumulates in muscles. This is what causes the fatigue and pain you feel after say 15 repetitions of leg squats, and why muscles stop being able to contract and relax. Muscles need ATP to power them, and to make ATP they need oxygen. Some exercises are intense and do not supply the body with oxygen fast enough to meet the demands placed on the body. This results in the buildup of lactic acid. The way to remove the lactic acid from muscles is by resting and breathing in oxygen for cellular respiration to occur.
*Students will work in pairs to complete 4 exercises (tasks). Each student must participate in each exercise. While one student is doing the exercise, the other student will be timing the other and writing down the numbers for each trial. They should write the 4 data tables in their science notebook before they begin the exercise lab. Tell students to make a prediction before each task on how long they can go before their muscles tire out.
Materials:
Stopwatch
Science journal/notebook
Stress ball, tennis ball, or grip strength trainer
Chair
Task #1- Bicep Curl Exercise
Stretch out your arm with your palms facing upward. Make sure to use your non-dominant hand, so if you are left-handed, you will use your right arm. Do a bicep curl, by bending your arm at your elbow to raise your hand. Then lower your hand by straightening your arm. While you perform this task, keep firm and steady muscle movements.
Continue to do this exercise for a minute. Raise and lower your arm quickly, but carefully so as not to hurt yourself. Your partner will record the time using a stopwatch and will count how many times you do this task in a minute. After each minute, this person will record the number of repetitions in your data table.
Repeat step 2 for 7 more times. Do not stop between trials (Each minute is one trial and you will do a total of 8 trials).
When 8 trials have been completed and the numbers for each trial has been documented, you will switch roles with your partner and repeat steps 1-3. Remember to work hard, this should not be a “stroll in the park” :). Do not stop between trials.
Student #1Data
1 min ____ 2 min ____ 3 min ____ 4 min ____ 5 min ____ 6 min ____ 7 min ____ 8 min ___
Student #2 Data
1 min ____ 2 min ____ 3 min ____ 4 min ____ 5 min ____ 6 min ____ 7 min ____ 8 min ___
1. Find a sturdy chair. You will sit on it and then stand up by using your hands to push
up. Then sit back down. This one repetition.
2. Do this for 3 minutes (3 trials). It should be a steady sit to stand motion, pretty
continuous. You do not have to go fast, just a steady pace.
3. While one of you is doing the exercise, the other one is timing and recording the
numbers of repetitions in the data table for EACH minute or trial. Remember not to
stop between trials or during each repetition. After each minute or trial, the student
doing the exercise keeps going until all trials are completed.
4. Switch roles with your partner.
Student #1Data
1- minute ________ 2- minutes ________ 3- minutes ________
Student #2 Data
1- minute ________ 2- minutes ________ 3- minutes ________
Task #3- Finger Flex and Extend Exercise
1. Using your non-dominant hand, grab a tennis all or a stress ball (one that is more firm
than squishy). Give the ball a good squeeze. Keep squeezing for ten seconds.
2. Your partner will record the number of squeezes you did in your data table for ten
seconds. Continue squeezing. Do not stop between trials. Each ten seconds that
passes the timer student will record how many times you squeezed the ball in those
ten seconds. Keep doing this exercise until 100 seconds have passed (10 trials).
3. When you are done, switch roles with the other person.
Student #1Data
10 sec __ 20 sec __ 30 sec _ 40 sec _ 50 sec _ 60 sec _ 70 sec _ 80 sec _ 90 sec _ 100 sec _
Student #2 Data
10 sec __ 20 sec __ 30 sec _ 40 sec _ 50 sec _ 60 sec _ 70 sec _ 80 sec _ 90 sec _ 100 sec _
*For the squeeze task, you could use a grip strength trainer too if you prefer this over a
tennis ball or firm stress ball.
Task # 4- Calf Raises Exercise
1. Stand with legs about 2 feet apart. Raise both heels and stand on your toes. Then
return your heels back to the ground.
2. One student will perform the exercise while the other one times and records the
number of calves raises done each 10 seconds (one trial). Write this number in the
data table every 10 seconds. Like the other exercises, do not stop between trials.
Keep going. The timer will watch the clock and record while the other focuses on
doing the task.
3. Keep this going for 10 trials (100 seconds).
4. Switch roles.
Student #1 Data
10 sec _20 sec _30 sec _ 40 sec_ 50 sec__ 60sec __ 70 sec__ 80 sec __ 90 sec _ 100 sec _
Student #2 Data
10 sec _20 sec _30 sec _ 40 sec_ 50 sec__ 60sec __ 70 sec__ 80 sec __ 90 sec _ 100 sec _
Post-Lab Questions:
1. In task #1, how long did it take for your arm muscles became very fatigued? Did you
complete all the trials for each task? If not, why? Describe how you felt at the end of
your task.
2. In task #2, how did your leg muscles feel at the end of the trials? How long did you go
before your legs became very fatigued? Did you have to stop at any point due to any
pain? If so, at what trial? How did you feel at the end of the task?
3. In task # 3, how long did it take before your hand muscles became very fatigued?
Were you able to squeeze non-stop for all 10 trials? If not, at which trial did you stop
and why?
4. Which type of muscle in the human body contracts and relaxes continuously in a
repeating rhythm and never tires? Is this a voluntary or involuntary muscle? Are you
more appreciative of this muscle after doing this lab?
5. In task #4, how long did it take for your calf muscles to be overly fatigued?
Was there a point you had to quit before completing all the trials? If so, which trial
and why? Describe how your muscles felt at the end of the task.
6. __________ __________ accumulates and builds up in muscles during intense
physical activity because the body breaks down glucose for energy faster than it can
supply the cells with_____________. This is what causes you to feel _____________ and
_____________ after many repetitions of exercise in a short time.
7. If you could do these tasks over being able to rest 5 minutes between trials, do you
think you would have had different results? How so, and why?
8. For each task, how long did it take for the burning feeling and pain to disappear?
9. Do you exercise regularly? How about your lab partner? Looking at your data table,
which one of you experienced muscle fatigued more easily? Give three reasons a fit
person can do more repetitions before tiring and feeling pain that a non-fit person.
10. What is oxygen debt and what role did it play in this lab?
If you would like a student worksheet to add to your muscular system unit, I have a FREE graphic organizer on the 3 types of muscles you can download. The muscles targeted in this lab are the skeletal muscles, so you can include this lab in your muscular system lessons or in your cellular respiration lessons. You might just want to change up some of the post lab questions in this lesson if you choose to do it for the muscular system unit because some of the questions relate to cellular respiration (in case your students have not learned this yet).
