This was the fifth and final regular Investigation of the LabLearner CELL Examining Exercise.

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

1. Students should first take and record their resting heart rates in the appropriate column of their Physical Fitness Log before beginning their exercises.

2. Each student should perform their exercise, either the leg lift for 1.5 minutes for each leg, or jumping rope for four minutes.

3. After students have completed their exercises, they should immediately take and record their heart rates in their Physical Fitness Log.

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B. Begin analysis of the experiments from this Investigation by reminding students that in Trials 1 and 2 they tested the effects of practice on performance.

1. Ask students:  Can you summarize what was done in Trials 1 and 2? Students performed two different tasks, one with beans and one with bears.  In both Trials, they had to complete the tasks with both their left and right hands and compare whether they were better at the tasks with one hand or another.

2. Ask students:  What were your results from Trials 1 and 2:  Were you better at the tasks with one hand as compared to the other?  Students should indicate that they were better at both tasks when using their dominant as compared to their non-dominant hand.  That is, they were able to transfer more beans with fewer spilled on the table and slide more bears into the liter pitcher with their dominant hand.  However, some students may have noticed a similar proficiency with both hands.

3. Ask students:  Why do you think you achieved more success with one hand?  Can you describe your answer in terms of practice?  Students should suggest that they have a dominant and non-dominant hand.  They have a hand that they use more often than the other for everyday tasks such as eating and writing.  They should associate the number of times they use their dominant hand as compared to their non-dominant hand with a difference in practice.  The practice comes in the form of practicing reaching, grabbing, and writing.  Because the muscles of one hand receive more practice, they can perform tasks more easily.  If students were to practice the actions with the non-dominant hand, the tasks would become easier to perform with that hand.  However, it is possible that some students display similar efficiency with both hands as a result of practice related to sports or music.  Students should be able to discuss any similarities between hand performance by relating it to these examples of additional types of practice.

4. Ask students: Based on the results of Trials 1 and 2, what are the benefits of practice? Student answers may vary but should include the following:  muscles become less fatigued, a skill takes less thought to perform (becomes automatic), individual skills can be performed automatically in a series (an example would be catching a ball then throwing it to a teammate), muscles perform a skill more efficiently, practicing basic skills makes it easier to learn more complicated skills.

5. Tell students that Olympic athletes often spend hours practicing a single skill over and over until the motion is automatic to them.

6. Ask students:  What are some skills that Olympic athletes might want to be automatic? Students’ answers will vary but may include such things as catching a ball, hitting a hockey puck, blocking a shot on goal, jumping a hurdle, executing a dive, etc.

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C. Remind students that the experiments in Trials 3-5 focused on applying the principles of physics to performance.

1. Tell students to recall the rubber band demonstration.

a.   If necessary repeat the demonstration:

b. Remind students that the rubber band was a model for a muscle.

c. Ask students:  What happened to the kinetic energy of the rubber band when we stretched it completely, compared to stretching it only halfway? The kinetic energy increased when the rubber band was stretched completely.   The rubber band moved a greater distance after it was stretched more completely than when stretched halfway.

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2. Encourage students to review the results of Trial 3.  Remind students of the questions about kinetic energy and performance.  

Ask students:  Did you observe kinetic energy in this experiment? When? Yes.  Kinetic energy was present as students jumped.

3. Ask students:  Did you observe a difference in kinetic energy between the two jumps?  Can you relate the differences in kinetic energy and the way you jumped to the demonstration with the rubber band?  Greater kinetic energy results in greater motion.  Therefore, the longer jump was the result of more kinetic energy. The longer jump was also that performed with bent knees. Thus, bending the knees when jumping produces more kinetic energy.  As the knees bend, the quadriceps or thigh muscles stretch further as compared to the muscles when standing straight.  Similar to the rubber band, the greater stretch translates into greater kinetic energy during muscle contraction.

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4. Discuss the question of torque and performance.  Direct students to review the results of Trial 4.  

Ask students:  Did you observe a change in kinetic energy between the arms-only swing and the full swing?  How do you know?  Yes.  The movement of the plastic dropper was greater with the full swing, indicating that it had greater kinetic energy than when the arms-only swing was performed.

5. Remind students that the force of rotation is called torque.  

Ask students:  Did you observe torque being used in Trial 4?  Where did you observe torque?  Was there a difference in torque between the two swings?  Yes.  Torque was easily observed in the twisting of the legs, hips, and body during the full swing and to a slight degree, the twisting of the upper body in the arms-only swing. There was more torque produced during the full swing.

6. Ask students:  How did torque affect kinetic energy in the baseball swing?  Why was there more torque in the full swing? When the arms-only swing was performed, students did not move their legs or hips and therefore the upper part of their body moved minimally in its position.  However, when students performed the full swing, they involved their hip joint which allows for circular motion around the joint and the production of a larger amount of torque.  As the hips and legs became involved, the rotation or torque also rotated the upper body.  The result was almost 180^o of motion and a much larger amount of kinetic energy produced during the final swing.

7. Ask students: Which swing would make a ball travel farther when hit? Why? The full swing would make the ball travel farther because the torque from the twisting of the batter’s body adds more kinetic energy to the swing and thus a hit ball.

8. Direct students to answer Problems 8-9 in the Student Data Record.

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D. Remind students of the experiment they performed in Trial 5.  They tried starting a race from a standing and a crouched position.

1. Encourage students to review the results of Trial 5.

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2. Explain to students that physics laws state that an object’s path follows the direction of its center of mass or the location of most of the object’s mass.  Use the following demonstration to illustrate this principle of physics:

a. Tell students to stand beside their desks and stand on tip-toe.  Allow students to remain in this position until they start to lose their balance.  

Ask students:  What happens when you start to lose your balance? Student answers will vary depending on the direction their bodies moved when they lost their balance, but should indicate that students fell forward or sideways.

b. Next direct students to stand with their feet flat on the floor.  Tell students to rock back on their heels by lifting the front of their feet off the floor.  

Ask students:  Which direction did your body move when you took the weight off the front of your feet? Students should indicate that they fell backward.

c. Explain to students that their bodies leaned forward or backward based on the direction their mass moved.  When they were on tiptoes, most of their mass or center of mass was in the forward direction.  When they were on their heels, most of the mass was directed backward.  

Ask students:  Was it easier to follow your body or try to regain your balance? Students should indicate it was easier to follow their bodies.

3.  Explain to students that it is easier to follow your body mass than try to change its direction.  

Ask students:  Describe how the experiment you just performed is related to the crouching and standing positions you performed in Trial 5.  Why do you think crouching would help you win the race? The crouched position puts most of the body weight or center of its mass forward, so it is heading in a forward direction. When the body is standing, most of the body weight or center of mass is behind the legs, positioned in a direction away from the direction the runner wants to go.  This forces him or her to change the direction of his or her body weight before moving forward.  This direction change costs the runner valuable time. Students observed this as the crouched runner’s shoulders extending farther in front of the starting line than the standing runner’s shoulders.

4. Instruct students to use what they learned in the balancing exercise to answer Problem 10 in the Scientist Data Record.

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E. Explain to students that Olympic athletes use the principles of physics to adjust their technique to improve their ability to perform basic skills more effectively, which in turn improves their performance. Ask the following questions to promote students’ understanding of the importance of kinetic energy and torque in physical activity:

a. Ask students: How can we change technique to increase kinetic energy? We can change technique by finding ways to increase muscle stretch, which increases kinetic energy when the muscle contracts.

b. Ask students: How can increasing kinetic energy improve performance? Increasing kinetic energy can help increase speed and distance.

c. Ask students: How can adding torque to technique improve performance? Adding torque can increase the amount of kinetic energy produced when performing a sport.

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F. Conclude the CELLe by explaining to students that they are going to complete their analysis of the exercises they have been performing during the five Investigations.

1. Direct students to turn to their Cardiovascular and Muscular Training Graph in the Student Data Record and complete the graphs they started during Investigation 3. Provide 15-20 minutes for completion of the graphs (see sample charts on this and the next slide).

2. Once students have completed their graphs, help them analyze and draw conclusions from them.

3. Focus students’ attention on the duration of time they performed the exercises.  

Ask students:  How long did you jump rope or do leg lifts in the Lab of Investigation 1 and the Post-Lab of Investigation 5? Leg lifts were performed for two minutes and jumping rope was performed for five minutes.

4. Ask students:  After the Lab of Investigation 1, what happened to the duration of exercise? Students should indicate the duration decreased in the Post-Lab of Investigation 1 and then slowly increased over the Investigations, ending at the highest duration in Investigation 5.

5. Ask students:  Why do you think the experiment was designed this way? Students may have difficulty answering this question.  Help students understand that the experiment was designed to show the effect of cardiovascular and muscular training on heart rate, cardiovascular endurance, and muscular endurance.  The gradual increase in duration represented the training component.  However, in order for students to compare their fitness levels from the start to the end of the experiment, they had to try to do the exercises for the maximum amount of time at the beginning and end.

[CONTINUED ON NEXT SLIDE]

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6. Ask for a show of hands:  Ask students: How many students were able to do their leg lifts or jump rope activity for the full amount of time the first week?  How many were able to do their leg lifts or jump rope activity for the full time this week? Most students should indicate it was more difficult to complete the tasks during the first week.

7. Ask students:  How did you feel at the end of your exercises the first week? Student answers may vary, but should include comments indicating muscle fatigue and/or soreness, increased heart rate, and increased breathing rate.  Some students may also indicate feeling hot or sweating.

8. Ask students:  What was different about how you felt after your exercises this week compared to the first week?  Why do you think you felt different? Student answers may vary but should indicate that students felt less muscle fatigue, and had an easier time breathing and completing the exercises.  The reasons given should indicate the students’ understanding that these changes occurred because cardiovascular, respiratory, and muscle endurance increased as a result of training or regularly performing the exercises.  Students should refer to the concepts learned in Investigations Two, Three, and Five in order to support their answers.  As activities are performed regularly or practiced, they become easier to perform and more automatic.  In this sense, the students should have found greater ease with the technical and balance aspects of the exercises.  Students performing the jump rope activity would have increased their cardiovascular endurance, their hearts and lungs would be able to deliver oxygen and nutrients faster and more efficiently because of this training, and their muscles would not be as fatigued because of increased muscle endurance.  For students performing leg lifts, their muscles would not cramp as readily because of increased muscle endurance and the ability of oxygen to get to the muscle.

9. Direct students to study their heart rate graphs, and ask students what conclusions they can draw from their graphs:

Ask students:  Did the leg lifts and jump rope have the same effect on heart rate?  No.  Jumping rope produced a greater increase in heart rate than leg lifts.  The value for heart rate during jumping was greater each week than that for leg lifts. Jumping rope involves more muscles than leg lifts.  The body would require more oxygen during this exercise than the leg lifts and the heart would need to beat faster to provide the body with oxygen during the jump rope activity than the leg lift activity.

Ask students: Compare the heart rate over the course of the Core Experience for both the leg lifts the jumping rope activity.  What happened to the heart rate?  As the duration of exercise increased, the heart rate increased because the body needed to provide the muscles with increased amounts of oxygen and nutrients.

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Conclude the analysis by posing the following questions:

Ask students: Are there any other indications that cardiovascular fitness improved over the course of this experiment?  Cardiovascular training also produces an increase in the volume of the left ventricle, enabling a greater volume of blood to be pumped with each heartbeat. This results in a lower resting heart rate.  Depending on their initial level of fitness, students may observe a decrease in their resting heart rate over the course of their experiment.  If students do not, discuss possible reasons such as:

• The training period was not long enough to see an effect
• Students’ level of physical fitness may already have been such that they already possessed low resting heart rates.

However, point out that even if their resting heart rate did not change, students likely noticed other benefits such as increased cardiovascular and muscular endurance. 

Ask students: Which partner do you think showed greater improvement in their cardiovascular fitness over the course of this experiment?  Why do you think so? Student answers will vary, but students who did the jump rope activity should have shown greater improvement in cardiovascular fitness.  Indications of this would include either a greater difference in beginning and ending resting heart rate or an initial increase of post-exercise heart rate followed by a gradual decrease at the end of the five weeks.  The students jumping rope were using more muscles for a longer period of time each week, and therefore their cardiovascular systems would have been working harder during the exercise period than their partners’ cardiovascular systems.