# Student Activity - Finger marathon

## Activity idea

By the end of this activity, students should understand:

• how muscles use energy doing exercise
• what happens to the muscle during recovery after exercise

## Instructions

The aim of this activity is to demonstrate muscle fatigue.

### What you will need

• spring operated clothes peg (plastic)
• stopwatch or cell phone (for timing)
• paper and pen for recording data.

### Instructions:

Work in pairs.

1. Hold the clothes peg comfortably with the thumb and forefinger of the hand you write with as shown.

2. Practise quickly opening and closing the clothes peg for a few seconds. (Make sure you open it all the way each time you do it).
3. Your partner will be the timekeeper and will count the number of times you can close the clothes peg in 30 second (s) intervals. Before you start, draw up a table for your data: Number of squeezes for each student.

Number of squeezes for each student.

Person number

30s

60s

90s

1

2

4. When your timekeeper says go, open and close the peg as fast as you can. Count out loud each time you repeat the movement.
5. The timekeeper will write down the numbers at 30 s, 60 s and 90 s.
6. Repeat the experiment switching timekeeper and clothes peg squeezer roles with your partner. Record their number of squeezes.
7. Draw and plot a graph of the two sets of results. (X axis = 30 s, 60 s, 90 s. Y axis = number of squeezes per 30 s interval).
8. Discuss the results with your partner and be prepared to talk about the following ideas in a class discussion.
9. Was there any difference in the number of squeezes you were able to do?
10. Describe the feeling in your finger muscles during different stages of the experiment.
11. Use the graph to predict the interval (in blocks of 30 seconds) when you would no longer be able to squeeze the clothes peg.
12. Carry out an experiment to test this prediction.
13. Record the class results. Average the results at each 30 s interval and add the average class results to your individual graph. Compare these with your individual results.

### What’s happening?

At the early stage of this activity your cells are using energy that has been generated from aerobic respiration (using oxygen and releasing carbon dioxide). The muscle fibres that carry out this oxygen-involving respiration are called slow twitch muscle fibres.

After a while, oxygen can’t be delivered fast enough to these muscle fibres and fast-twitch muscle fibres are recruited, which are able to release energy through anaerobic respiration (respiration that doesn’t need oxygen). The downside of this reaction is that less energy is produced and the waste product is lactic acid. When lactic acid accumulates in the muscle it interferes with muscle contraction and you are aware of a 'burn' with lactic acid build up.

In the recovery stage (when you are having a rest), oxygen is restored to the muscles and the lactic acid is removed from the muscles cells by the blood.

Most people don’t exhaust their supply of energy because muscular fatigue and pain usually cause them to stop their activity. Marathon runners may push beyond pain and sometimes they collapse because there is no more energy to keep their muscles moving.