Muscle Contraction Lab - PC\|MAC



Muscle Contraction Lab

Objectives:

Demonstrate muscle tone. Demonstrate muscle fatigue.

Process Skills:

Measuring changes in muscle size and organizing data in tables

Materials:

tape measure tennis ball

5-7lb. weight stopwatch or second hand

Background:

1. What are the 2 protein filaments that are abundant in muscle cells and allow them to contract?

________________ and _______________

2. Explain how these 2 filaments work together to allow a muscle to contract.

______________________________________________________________________________________________________________________________________________________

3. How do smooth and cardiac muscle tissue differ from skeletal muscle?

___________________________________________________________________________

Technique:

Part A: Muscle Tone

1. Select one member of your group to perform the following tasks. In each case, note the degree of biceps brachii contraction by measuring the circumference of the upper arm with a measuring tape.

a. Sit comfortably with your forearms on the table, palms down. _______ inches

b. Sit comfortably in the same position, but this time with palms up. Note differences, if any.

_______ inches.

c. Sit comfortably, grasp the weight and lift it with your palms facing up. This is called a weight curl. _______ inches.

Under which of the above conditions did you see the greatest degree of muscle tone?

_________________________________________________________________________

2. Select one member of your group to perform the following tasks (choose an individual wearing shorts or wearing pants that are more form fitting). In each case, note the degree of contraction of the gastrocnemius muscle by measuring the circumference of the lower leg (at its widest point) with a measuring tape.

a. Sit on the edge of a chair with both feet on the floor. _______ inches

b. Sit on the edge of a table with feet dangling. _______ inches

c. Stand up straight and lock knees for 5 seconds. _______ inches

d. Stand up straight with legs relaxed. _______ inches

e. Stand on toes, extend arms overhead, and reach for the ceiling. _______ inches

Under which of the above conditions did you see the greatest degree of muscle tone?

___________________________________________________________________________

Part B: Muscle Fatigue

1. Select one member of your group to perform this exercise.

2. Hold the tennis ball in you right hand and squeeze the ball repeatedly as quickly as your can. Count the number of complete contractions during each 10-second interval for a total period of 3 minutes (180 sec). Record the number of contractions during each 10-second interval in the table labeled Right hand: Trial 1.

3. Relax for 1 minute and repeat step 2 using your right hand again. Record the number of contractions during each 10 second interval for a total period of 3 minutes (180 sec) or until fatigue occurs. Record the number of contractions during each 10 second interval in the table labeled Right hand: Trial 2.

4. Wait for 5 minutes, repeat step 2 again, and record your data in the table labeled Right hand:

Trial 3.

5. Now repeat steps 2-4 with your left hand. Record all data in the tables labeled Left hand: Trial 1, Trial 2 (after 1 minute rest), and Trial 3 (after 5 minute rest).

Result and Analysis:

1. What is muscle fatigue? __________________________________________________________

2. Were differences in muscle fatigue found between the right and left hands?

___________________________________________________________________________

3. What factor(s) might account for the differences between the left and right hand?

___________________________________________________________________________

4. What role does regular exercise play with regard to muscle fatigue? _______________________

______________________________________________________________________________________________________________________________________________________

Clean up your lab space and return all lab materials to the front of the room.

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