This was the third Investigation of the LabLearner CELL Examining Exercise.

______________________________________________

A. Begin this part of the Investigation by directing students to locate their Physical Fitness Log at the end of their Student Data Record.  Ask students to organize into their exercise pairs.

1. Direct students to follow the same procedure to complete their exercises as during the PreLab.

2. Students should first take and record their resting heart rates in the appropriate column before beginning their exercises.

3. Each student should perform their exercise, either the leg lift for each leg for one minute or the jump rope activity for three minutes.

4. After students have completed their exercise, they should immediately take and record their heart rates in the appropriate column of the Physical Fitness Log.

______________________________________________

B. Begin the analysis of the Lab by asking students to summarize the experiments they conducted and their purpose.

1. Ask students: What were the main questions we investigated in the Lab? How do muscles work in pairs to move parts of the body?  How does muscle fatigue affect your ability to exercise?  How does your muscular flexibility affect your muscular fitness?

2. Ask students: How would you summarize the experiments you performed in the Lab to answer those questions? Students analyzed three different muscle pairs to determine how their interaction provides the body with the ability to move.  They performed an exercise that illustrated what muscle fatigue feels like and analyzed how muscles can become locked in a contraction.  Students also used a balloon as a flexibility model and compared it to the stretching of a muscle.

______________________________________________

C. Continue to review the Lab experiments.  Students may wish to refer to their Student Data Record during the review.  Ask students the following questions to prompt discussion:

1. Ask students: You investigated how several muscle pairs produced movements of the body.  Can you describe which pairs you used and which part of the body each muscle moved? Within each pair of muscles, each muscle moved the body in an opposite direction from the movement of the other muscle.  The biceps and triceps muscle pair both moved the lower arm.  The biceps moved the lower arm up toward the shoulder.  From this position, the triceps moved the lower arm downward.  Both the abdominal muscles and erector spinae moved the chest in relation to the legs.  The abdominal muscle pulled the chest closer to the front of the legs.  The erector spinae pulled the chest away from the front of the legs.  The hamstrings and quadriceps both moved the lower leg.  The quadriceps straightened the lower leg.  The hamstrings helped the lower leg bend toward the upper leg.

2. Ask students: Which joints do you think were involved in each movement?

     Triceps and biceps: elbow joint

     Hamstring and quadriceps: knee joint

     Abdominal and erector spinae: vertebrae and hips

3. Ask students: Why do you think the triceps and biceps, hams and quadriceps, abdominals and erector spinae are called muscle pairs? Each set of muscles is referred to as a muscle pair because the muscles work to move the same joint, but in opposing directions.  They are paired together in terms of the joint they move.

4. Ask students: Can you describe how muscle pairs, such as the hamstrings and quadriceps, work together to move your leg? The quadriceps and hamstring muscles are located on opposite sides of a bone.  When sitting in a chair, the leg can be lifted off the floor when the quadriceps contract, or becomes shorter, and the hamstrings relax and become longer, or stretched.  The reverse occurs as the leg is lowered, the hamstrings contract as the quadriceps relax.

______________________________________________

5. Ask students: How do muscles work in pairs to move parts of the body? How is the function of the muscle pairs related to their location? Direct students to record the answer in Problem 6a of their Student Data Record. After students have had time to complete this task, discuss the answer.

The muscles investigated in the Lab were attached to opposite sides of a bone. When one of the muscles of the pair contracted and became shorter, the opposite muscle relaxed and became longer, or stretched.

6. Ask Students: Can both muscles in a muscle pair be in a state of contraction simultaneously? Yes. Students may have difficulty understanding that rarely does a muscle pair function in an all or none situation. In other words, while they observe one muscle of the pair contracting, they may assume the other has completely relaxed. While this is true to some extent, it is really a case of which muscle in the pair is contracting to a greater degree. Imagine the lower leg pulled up so the foot is almost touching the rear end and then slowly lowered. The lowering of the leg occurs primarily through contraction of quadriceps. Yet as this movement occurs, the hamstrings must also contract to a lesser degree to prevent the leg from suddenly hitting the floor. However, if both muscles contract with equal force, no movement will occur.

7. Ask students: Which question have we been able to answer? Students should recognize that they have answered the question about muscle pairs working together to move the body.

______________________________________________

D. Direct students to think about the second and third questions from their Investigation.

1. Explain that you would like students to think about the second question, which was about muscle fatigue.

2. Ask students: Which experiment caused you to experience muscle fatigue? The experiment in which students squeezed their partner’s index and middle fingers for 30 seconds produced muscle fatigue.

3. Ask students: How did your hand feel afterward? Students should indicate that it felt frozen in place and that the fingers felt stiff when they tried to open their hands.

4. Ask students: Why do you think you had difficulty opening your hand after squeezing for 30 seconds? How does muscle fatigue affect your ability to exercise? Direct students to record the answer in Problem 6b of their Student Data Record. After students have had time to complete this task, discuss the answer.

The muscles locked in a contracted position because they required more energy to move. As the hand continued to squeeze, the muscles were contracting and using oxygen and nutrients, the two components necessary to provide the muscles with energy. In addition to requiring energy to contract, muscles required energy to relax. Because all of the nutrients and oxygen were used by the muscles to contract, no energy was available for relaxation of the muscles. When the hand was allowed to rest after the 30 seconds, more oxygen and nutrients became available to the muscles and the hand was able to move from its locked position. 

The same phenomena produce rigor mortis, or the stiffness of muscles after death. As no additional energy is available to the body’s muscles, they become locked in their final contracted state. Later, the stiffness subsides. This does not occur because more oxygen and nutrients have reached the muscles, as in the lab experiment, but rather because the muscle tissue is slowly broken down.

5. Ask students: Was the muscle fatigue you experienced a long-term or short-term effect? It was a short-term effect because it did not have a lasting effect over a long time period.

6. Ask students: Have you answered the second question: How does fatigue affect your ability to exercise? Students should indicate they were able to answer the question.

______________________________________________

Encourage students to apply what they have learned to their own experiences with physical fitness. Use the following questions to help initiate the conversation.

1. Ask students: What do you think could be done to reduce muscle fatigue when exercising? Muscle fatigue can be reduced by slowly increasing the amount of time an exercise is performed. This will increase the ability of muscle to use oxygen more efficiently and will increase muscular endurance. That is, the muscle will be able to contract for longer periods without feeling fatigued.

2. Let’s turn to our final question. Ask students: How does your muscular flexibility affect your muscular fitness? Improving muscular flexibility by stretching muscles before and after exercise will allow the muscles to work at their maximum capacity. Activity to which the body is not accustomed can increase the chances of muscle tears and cramping.

3. Ask students: Why do you think Olympic athletes perform stretching exercises before and after their performances? Direct students to reflect on Trials 5 through 7 from the Lab, then record the answer in Problem 6c of their Student Data Record. After students have had time to complete this task, discuss the answer

Gradually stretching muscles to their maximum before exercise, or warming up, prepares the muscles for strenuous exercise. This helps prevent muscles from tearing and prevents the shock of immediate participation in intense levels of physical activity to the body. Stretching after intense physical activity, or cooling down, allows the muscles to slowly return to a normal state. This prevents cramping or blood from settling in the muscles, which can result in a feeling of muscle soreness.

4. Ask students: Have you answered the third question about muscle flexibility? Students should indicate they were able to answer the question.

5. Ask students: Does muscular fitness and muscular endurance also apply to your heart? Yes. The heart is a muscle and its muscular fitness can change through cardiovascular exercise.

6. Ask students: What can you do to improve your muscular fitness? Regular physical activity will improve muscular endurance and flexibility, which can improve overall muscular fitness.

______________________________________________

Provide for some additional time for students to continue to develop their bar graphs. 

Students should locate the Cardiovascular and Muscular Training page in their Student Data Record. Students may wish to refer to the Creation and Completion of a Bar Graph from their Procedural Toolbox as they work on their graphs.

1. Ask students to organize into the same groups they were in previously for this activity.

2. Inform students they will next insert the data from their Physical Fitness Log that they have collected thus far.

3. Remind students that they will need a legend to distinguish between the columns that represent their resting heart rate and their heart rate after their exercise (leg lifts or jumping rope).

4. After students have finished inserting their data, explain that they will continue to add to their bar graphs throughout the CELL.

NOTE: Analysis of students’ bar graphs is performed during Investigation Five.

______________________________________________

To complete this Investigation, tell students they will explore the importance of a healthy lifestyle and how that relates to physical fitness in the next lesson. Questions they will explore include:

Can what you eat affect your physical fitness?

How does what you eat affect your energy balance?