How Does the Strength of Muscles Affect Fatigue Over Time?
Purpose/Hypothesis
In this experiment you will examine if a muscle can increase the number of contractions with muscle use, thereby reducing muscle fatigue. You will measure your muscle contractions through squats. The quadriceps muscles in the front of the upper legs are one of the main muscles used in a squat. A squat also uses the gluteus, hamstrings, and calf muscles.
A friend or family member will time the length of time you conduct the activity before you are fatigued. This partner will also count the number of squats you carry out and note them in a chart that you should not look at until you have completed the entire experiment. Not allowing you to know the number of muscle contractions you have completed will make the experiment more objective by not giving you a number to "beat." Try to think of something else during the experiment so you do not count the squats for yourself.
A hypothesis should be brief, specific, and measurable. It must be something you can test through further investigation. Your experiment will prove or disprove whether your hypothesis is correct. Here is one possible hypothesis for this experiment: "The stronger muscles will become less fatigued and will gain strength over time."
In this case, the variable you will change is the strength of the muscles. The variable you will measure is the number of times your muscles can contract. To equate all the other variables, conduct the experiment at roughly the same time of day. At the end of the experiment you will examine how your muscles have changed over time.
What Are the Variables?
Variables are anything that might affect the results of an experiment. Here are the main variables in this experiment:
- The time of day
- Your nutritional level before you conduct the trial
Level of Difficulty
- Easy
Materials Needed
- partner
- watch with second hand
Approximate Budget
- $0
Timetable
- Approximately 5 minutes per trial for a period of ten trials.
How to Experiment Safely
Working a muscle too hard can cause soreness and damage to your muscle. Stop the activity if you feel dizzy or experience physical discomfort. Keep your feet firmly on the floor at all times and breathe regularly. If you have knee problems, do not do this experiment. Check with a parent or physical education teacher for a replacement activity.
Step-by-Step Instructions
- Have your partner begin timing when you start your first squat. Your partner will count the number of squats you do at each trial. Try to think of something else during the experiment so you do not count the squats for yourself.
- To conduct the squat, get into a comfortable upright stance, with your feet shoulder-width apart and your toes pointed straight ahead. Don't point your toes inward, because this will put a lot of strain on your knees.
- Extend your arms. Squat down until your knees are over your toes. Pretend you are sitting in a chair.
- Make sure to keep your heels planted firmly on the floor.
- Return in an upright position and repeat at a regular pace.
- When your muscles become fatigued then stop. Have your partner note the number of squats and the amount of time. Do not look at the chart.
- Repeat this process every other day for a period of ten trials.
Summary of Results
Graph the results of your data from your first trial to the last trial, making the x-axis the number of squats and the y-axis the trial number. Does the number of muscles' contractions change over time? Construct a second graph that marks the length of time of each trial on the x-axis with the trial number on the y-axis. How does the length of time you were able to contract your muscles change over time? Write a brief summary of the experiment that relates your results to muscle strength and movement.
Troubleshooter's Guide
Problem: There is no change in muscle fatigue over the trials.
Possible cause: You may be squatting further down over the trials, which uses more muscle. Repeat the experiment making sure to stop your squat each time when your knees are over your toes.