MPrF-01CP H Y S I O E X 8 . 0 : M U S C L E P H Y S I O L O G Y – S I N G L E A N D M U L T I P L E S T I M U L U S

OBJECTIVES

1. To define these terms used in describing muscle physiology: multiple motor unit summation, maximal stimulus, treppe, wave summation, and tetanus.

2. To identify two ways that the mode of stimulation can affect muscle force production.3. To plot a graph relating stimulus strength and twitch force to illustrate graded muscle

response.4. To explain how slow, smooth, sustained contraction is possible in a skeletal muscle.

INSTRUMENTS

1. Laptop (brought by the students, min. 1 laptop/group)2. Internet access

PROCEDURES

I. ACCESSING THE PHYSIO EX 8.0 WEBSITE

1. Connect your laptop to the wireless internet access in the physiology laboratory.2. Open your browser, go to www.myaandp.com3. Click the Log In button in the lower left area of the page.4. Choose the Human Anatomy & Physiology, 8e book by Elaine Marieb &

Katja Hoehn 5. Type “faalui” in the Login Name.6. Ask your tutor to fill in the Password.7. Choose PhysioEx 8.0 at the lower left area of the page.

II. SINGLE STIMULUS

Choose Chapter 9: Skeletal Muscle Physiology from the menu, then click Single Stimulus. The opening screen will appear in a few seconds.

D E T E R M I N I N G T H E L A T E N T P E R I O D

1. Set the voltage to 5.0 volts and the muscle length at 75 mm.2. Drag the 200 msec button to the right edge of the oscilloscope.3. Click the Stimulate button once, and allow the tracing to complete.4. When you measure the length of the latent period from a printed graph, you measure the

time between the application of the stimulus and the beginning of the first observable re-sponse (increase in force). The computer can’t “look ahead,” anticipating the change in active force. To measure the length of the latent period using the computer, click the Measure button. Then click the right arrow button next to the Time window repeatedly until you notice the first increase in the Active Force window. This takes you beyond the actual length of the latent period. Now click the left arrow button next to the Time window until the Active Force window again reads zero. At this point the computer is

MPrF-01Cmeasuring the time between the application of the stimulus and the last point where the active force is zero (just prior to contraction).

How long is the latent period? ________ msec

What occurs in the muscle during this apparent lack of activity?

I N V E S T I G A T I N G G R A D E D M U S C L E R E S P O N S E T O I N C R E A S E D S T I M U L U S I N T E N S I T Y

1. Click Clear Tracings if there are tracings on your screen.2. Set the voltage to 0.0 and the muscle length at 75 mm, and click Stimulate.3. Click Record Data. 4. Repeat steps 2 and 3, increasing the voltage by 0.5 each time until you reach the

maximum voltage of 10.0. Be sure to select Record Data each time.5. Observe the twitch tracings. Click on the Tools menu and then choose Plot Data.6. Use the slider bars to display Active Force on the Y-axis and Voltage on the X-axis.7. Use your graph to answer the following questions:

What is the minimal, or threshold, stimulus? ________ V

What is the maximal stimulus? ________ V

How can you explain the increase in force that you observe?

8. Click Print Plot at the top left corner of the Plot Data window and choose Adobe PDF as the printer to save the graph in PDF format (attach the graph in your lab report). When finished, click the X at the top right of the plot window.

9 . Click Tools Print Data and choose Adobe PDF as the printer to save the graph in PDF format (attach the data in your lab report).

I N V E S T I G A T I N G T H E E F F E C T O F M U S C L E L E N G T H O N T H E S T R E N G T H O F M U S C L E C O N T R A C T I O N

1. Click Clear Tracings if there are tracings on your screen.2. Click Clear Table to erase your previous data.3. Set the voltage to 5.0 volts and the muscle length at 50 mm, and click Stimulate.4. Click Record Data. 5. Repeat steps 2 and 3, increasing the muscle length by 5 mm each time until you reach

the maximum muscle length of 100 mm. Be sure to select Record Data each time.6. Observe the twitch tracings. Click on the Tools menu and then choose Plot Data.7. Use the slider bars to display Active Force on the Y-axis and Muscle Length on the X-

axis.8. Use your graph to answer the following questions:

What is the optimum muscle length for active force? ________ mm

How can you explain the increase and decrease in active force that you observe?

9. Click Print Plot at the top left corner of the Plot Data window and choose Adobe PDF as the printer to save the graph in PDF format (attach the graph in your lab report). When finished, click the X at the top right of the plot window.

MPrF-01C10. Click Tools Print Data and choose Adobe PDF as the printer to save the graph in

PDF format (attach the data in your lab report).

III. MULTIPLE STIMULUS

Choose Multiple Stimulus from the Experiment menu. The opening screen will appear in a few seconds.

I N V E S T I G A T I N G T R E P P E

1. The voltage should be set to 8.2 volts, and the muscle length should be 75 mm.2. Drag the 200 msec button to the center of the X-axis time range. 3. Be sure that you fully understand the following three steps before you proceed:

i. Click Single Stimulus. Watch the twitch tracing carefully.ii. After the tracing shows that the muscle has completely relaxed, immediately click

Single Stimulus again.iii. When the second twitch completes, click Single Stimulus once more and allow the

tracing to complete.4. Click Tools Print Graph and choose Adobe PDF as the printer to save the graph in

PDF format (attach the graph in your lab report).

What happens to force production with each subsequent stimulus?

I N V E S T I G A T I N G W A V E S U M M A T I O N

1. Click Clear Tracings to erase the oscilloscope display.2. Set and keep the voltage at the maximal stimulus (8.2 volts) and the muscle length at 75

mm.3. Drag the 200 msec button to the right edge of the oscilloscope display unless you are

using a slow computer.4. Click Single Stimulus, and then click Single Stimulus again when the muscle has

relaxed about halfway. Unlike the previous experiment, we will not allow the muscle to completely relax.

Is the peak force produced in the second contraction greaterthan that produced by the first stimulus?

5. Try stimulating again at greater frequencies by clicking the Single Stimulus button several times in rapid succession.

6. Click Tools Print Graph and choose Adobe PDF as the printer to save the graph in PDF format (attach the graph in your lab report).

Is the total force production even greater?

MPrF-01C How does the frequency of stimulation affect the amount of force generated by the

muscle? Hint: Compare the force generated from a single click and from rapidly clicking Single Stimulus several times.

I N V E S T I G A T I N G F U S I O N F R E Q U E N C Y / T E T A N U S

1. Click Clear Tracings to erase the oscilloscope display.2. The voltage should be set to 8.2 volts, and the muscle length should be 75 mm.3. Adjust the stimulus rate to 30 stimuli/sec.4. The following steps constitute a single “run.” Become familiar with the procedure for

completing a run before continuing.i. Click Multiple Stimulus.ii. When the tracing is close to the right side of the screen, click Stop Stimulus to turn

off the stimulator.iii. Click Record Data to retain your data in the grid at the bottom of the screen and in

the computer’s memory. 5. Repeat steps 3 and 4, increasing the stimulation rate by 10 stimuli/sec each time up to

150 stimuli/sec.

How do the tracings change as the stimulus rate is increased?

6. When you have finished observing the twitch tracings, click the Tools menu, and then choose Plot Data.

7. Set the Y-axis slider to display Active Force and the X-axis slider to display Stimuli/sec.From your graph, estimate the stimulus rate above which there appears to be no significant increase in force: ________ stimuli/secThis rate is the fusion frequency, also called tetanus.

8. Click Print Plot at the top left corner of the Plot Data window and choose Adobe PDF as the printer to save the graph in PDF format (attach the plot in your lab report). When finished, click the X at the top right of the plot window.

I N V E S T I G A T I N G M U S C L E F A T I G U E

1. Click Clear Tracings to erase the oscilloscope display.2. The voltage should be set to 8.2 volts, and the muscle length should be 75 mm.3. Adjust the stimulus rate to 120 stimuli/sec.4. Click Multiple Stimulus, allow the tracing to sweep through three screens, and then click

Stop Stimulus to stop the stimulator.5. Click Tools Print Graph and choose Adobe PDF as the printer to save the graph in

PDF format (attach the graph in your lab report).

Why does the force begin to decrease with time? Note that a decrease in force indicates muscle fatigue.

6. Click Clear Tracings to erase the oscilloscope display. Keep the same settings as before.

7. You will be clicking Multiple Stimulus on and off three times to demonstrate fatigue with recovery. Read the steps below before proceeding.i. Click Multiple Stimulus.ii. When the tracing reaches the middle of the screen, briefly turn off the stimulator by

clicking Stop Stimulus, then immediately click Multiple Stimulus again.

MPrF-01Ciii. You will see a dip in the force tracing where you turned the stimulator off and then on

again. The force tracing will continue to drop as the muscle fatigues.iv. Before the muscle fatigues completely, repeat the on/off cycle twice more without

clearing the screen.8. Click Tools Print Graph and choose Adobe PDF as the printer to save the graph in

PDF format (attach the graph in your lab report).

Turning the stimulator off allows a small measure of recovery. The muscle will produce force for a longer period if the stimulator is briefly turned off than if the stimulations were allowed to continue without interruption. Explain why.

9. To see the difference between continuous multiple stimulation and multiple stimulation with recovery, click Multiple Stimulus and let the tracing fall without interruption to zero force. This tracing will follow the original myogram exactly until the first “dip” is encountered, after which you will notice a difference in the amount of force produced between the two runs.

10. Click Tools Print Graph and choose Adobe PDF as the printer to save the graph in PDF format (attach the graph in your lab report).

Describe the difference between the current tracing and the myogram generated in step 7.

MPrF-02CP H Y S I O E X 8 . 0 : M U S C L E P H Y S I O L O G Y – I S O M E T R I C A N D I S O T O N I C C O N T R A C T I O N

OBJECTIVES

1. To graphically understand the relationships between passive, active, and total forces.2. To identify the conditions under which muscle contraction is isometric or isotonic.3. To describe in terms of length and force the transitions between isometric and isotonic

conditions during a single muscle twitch.4. To describe the effects of resistance and starting length on the initial velocity of shortening.5. To explain why muscle force remains constant during isotonic shortening.

INSTRUMENTS

1. Laptop (brought by the students, min. 1 laptop/group)2. Internet access

PROCEDURES

I. ACCESSING THE PHYSIO EX 8.0 WEBSITE

1. Connect your laptop to the wireless internet access in the physiology laboratory.2. Open your browser, go to www.myaandp.com3. Click the Log In button in the lower left area of the page.4. Choose the Human Anatomy & Physiology, 8e book by Elaine Marieb &

Katja Hoehn 5. Type “faalui” in the Login Name.6. Ask your tutor to fill in the Password.7. Choose PhysioEx 8.0 at the lower left area of the page.

II. ISOMETRIC CONTRACTION

1. Choose Chapter 9: Skeletal Muscle Physiology from the menu, then choose Isometric Contraction from the Experiment menu. The opening screen will appear in a few seconds.

2. The voltage should be set to the maximal stimulus (8.2 volts), and the muscle length should be 75 mm.

3. To see how the equipment works, stimulate once by clicking Stimulate. You should see a single muscle twitch tracing on the left oscilloscope display and three data points representing active, passive, and total force on the right display. The yellow box represents the total force and the red dot it contains symbolizes the superimposed active force. The green square represents the passive force data point.

4. Click Clear Tracings to erase the oscilloscope display.5. Shorten the muscle to a length of 50 mm by clicking the (-) button next to the Muscle

Length window.6. Click Stimulate and, when the tracing is complete, click Record Data.

MPrF-02C7. Repeat the Stimulate and Record Data sequence, increasing the muscle length by 2

mm each time until you reach the maximum muscle length of 100 mm.8. Carefully examine the active, passive, and total force plots in the right oscilloscope

display.9. Click Tools Print Data and choose Adobe PDF as the printer to save the graph in

PDF format (attach the data in your lab report).

What happens to the passive and active forces as the muscle length is increased from 50 mm to 100 mm?

Explain the dip in the total force curve. Hint: Keep in mind you are measuring the sum of active and passive forces.

III. ISOTONIC CONTRACTION

1. Choose Isotonic Contraction from the Experiment menu. The opening screen will appear in a few seconds.

2. Set the voltage to the maximal stimulus (8.2 volts).3. Drag-and-drop the 0.5-g weight onto the muscle’s lower tendon.4. Platform height should be 75 mm.5. Click Stimulate and simultaneously watch the muscle action and the oscilloscope

tracing.6. Click the Record Data button to retain and display the data in the grid.

What do you see happening to the muscle during the flat part of the tracing? Click Stimulate to repeat if you wish to see the muscle action again.

Does the force the muscle produces change during the flat part of the tracing (increase, decrease, or stay the same)?

7. Return the 0.5-g weight to the cabinet. Drag the 1.5-gweight to the muscle. Click Stimulate, and then clickRecord Data.

Which of the two weights used so far results in the highest initial velocity of shortening?Weight : ________ gVelocity : ________ mm/sec

8. Repeat step 7 for the remaining two weights.

Weight : ________ gVelocity : ________ mm/sec

Weight : ________ gVelocity : ________ mm/sec

9. Choose Plot Data from the Tools menu.10. Set Weight as the X-axis and Total Force as the Y-axis by dragging the slider bars. Click

Print Plot at the top left corner of the Plot Data window and choose Adobe PDF as the

MPrF-02Cprinter to save the graph in PDF format (attach the plot in your lab report). When finished, click the X at the top right of the plot window.

What does the plot reveal about the relationship between resistance and the initial velocity of shortening?

11. Click Tools Print Data and choose Adobe PDF as the printer to save the graph in PDF format (attach the data in your lab report).

12. Click Clear Table in the data control unit at the bottom of the screen. Click Yes when you are asked if you want to erase all data in the table.

13. Return the current weight to the weight cabinet.14. Attach the 1.5-g weight to the muscle and run through the range of starting lengths from

60-90 mm in 5-mm increments. Be sure to click Record Data after each stimulus.15. After all runs have been completed, choose Plot Data from the Tools menu.16. Set Length as the X-axis and Velocity as the Y-axis by dragging the slider bars. Click

Print Plot at the top left corner of the Plot Data window and choose Adobe PDF as the printer to save the graph in PDF format (attach the plot in your lab report). When finished, click the X at the top right of the plot window.

Describe the relationship between starting length and initial velocity of shortening.

MPrF-02CM U S C L E P E R F O R M A N C E T E S T

If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health.

Hippocrates

In 1994, Bouchard and Shepard proposed a model describing the relationships among physical activity, fitness, and health. They defined fitness as "matching of the individual to his or her physical and social environment" and pointed out that the two goals of fitness were performance and health. Performance-related fitness was proposed to include motor skills; cardiorespiratory power and capacity; muscular power, strength, and endurance; body size; body composition; motivation; nutritional status; and genetics. Health-related fitness was defined as having "an ability to perform daily activities with vigor" and a low risk of developing degenerative diseases. The components of health-related fitness include body composition, strength and endurance, cardiovascular and respiratory function, and intracellular metabolism. Clearly, these two goals of fitness lie on a continuum.1

As clearly stated above, a musculoskeletal assessment is essential to determine a person’s overall fitness level. It can also identify specific areas of strength and weakness so a person will be able to plan his/her exercise accordingly.

In this lab work, you will try some of the available online muscle performance assessment re-written from ExRx.net (Exercise Prescription on the Net - http://www.exrx.net/index.html). Try these exercises on your group members. Try these exercises, and then write a group report as stated by the Guidelines of the Lab Report on Muscle Physiology (see attachment). The in-depth analysis will require you to explore various subject related to musculoskeletal work, sometimes from outside of the physiological standpoint.

PURPOSE

1. To evaluate muscle performance using a set of muscle performance tests.2. To analyze the individual and group result of muscle performance tests.

PREPARATION AND REQUIREMENTS

1. Read the following Lab Manual before the physiology lab session in order to understand the assessment techniques.

1. Every group member has to be the subject of each experiment.2. The subjects have to meet the following conditions:

a. healthyb. have no cardiovascular and musculoskeletal conditionsc. prepare themselves to perform the test on physiology lab session; therefore they are

required to:i. get enough sleep prior to the time of the test

1 Committee on Body, Composition, Nutrition, and Health of Military Women, Institute of Medicine: Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health (1998)

MPrF-02Cii. have lunch at least two hours before the time of the testiii. wear comfortable clothing suitable for doing exercise

LABORATORY WORK PROTOCOL

1. Do the sit up, push up, and vertical jump test on each group member.2. Calculate the result using a personal computer connected to the internet.3. Record the result and write a group report (see attachment: Guidelines for Muscle

Performance Test Report).4. The report is due 1 week after the laboratory work, and has to be submitted to the

Department of Physiology administration office (Tata Usaha Departemen Fisiologi).

MPrF-02CMUSCULAR ENDURANCE ASSESSMENT

Muscular endurance is the ability to sustain muscle contraction over a period of times without undue fatigue. No single endurance test measures the endurance of all muscles; however, the Sit Up Test serves as a measure of abdominal and hip flexor endurance while the Push Up Test indicate upper body strength and endurance.

Exrx.Net: Sit Up Testhttp://www.exrx.net/calculators/situps.html

Test Procedures

Subject performs as many bent knee sit-ups as possible within 60 seconds. Subject can rest between repetitions if unable to sit-up continuously. Subject should be encouraged to perform one or two trial repetitions before test. See online animation.

feet anchored by partner or apparatus knees bent 90° hands clasped behind neck elbows travel beyond or make contact with knees back of shoulders must return to floor

Result interpretation

Go to the indicated website. Enter information (sex, age and accurate repetitions) in left column; Click "Calculate". Record the result.

Sex

Age

Repetitions

Population Average

Score

Rating

REFERENCE NORM: Pollock ML, Wilmore JH, Fox SM: Health and Fitness through Physical Activity. New York John Wiley & Sons, 1978.

MPrF-02CExrx.Net: Push Up Testhttp://www.exrx.net/calculators/pushups.html

Test Procedures

The push ups must be completed using the following technique: hands are positioned directly under shoulders, elbows bend out on a 45º angle. The head must be tucked under, back straight and push ups lowered “nose fist distance from floor”. Women are allowed to use the “Ladies Push Ups” on their knees.

Subject performs as many repetitions as possible without pausing. Subject should be encouraged to perform one or two trial repetitions before test.

Elbows fully extended Male subject (See animation) forefoot or toes on floor legs, hips, and back straight tester places upright fist below chest of male subject contact with testers fist

Female subject (See animations: feet down, feet up) knees on floor or mat hips and back straight tester gives verbal feed back to female subject on depth of

push-up shoulders the same height of elbow

Result interpretation

Go to the indicated website. Enter information (sex, age and accurate repetitions) in left column; Click "Calculate". Record the result.

MPrF-02C

Sex

Age

Repetitions

Population Average

Score

Rating

REFERENCE NORM: Pollock ML, Wilmore JH, Fox SM: Health and Fitness through Physical Activity. New York John Wiley & Sons, 1978.

MPrF-02Cexrx.net: vertical jump testhttp://www.exrx.net/calculators/verticaljump.html

The Vertical Jump Test is a universal assessment of power. The subject is allowed three attempts at performing a depth jump and marking their progress in centimeters relative to their standing height. A measure of power is given relative to the height of the jump

Test Procedures

Put chalk on finger tips. Stand with side toward vertical jump apparatus and reach up as high as possible keeping the feet flat on the ground. Mark and record standing reach.

Stand slightly away from the apparatus. Jump up as high as possible using both arms and legs to assist in projecting the body upwards. Touch the measurement board at the highest point of the jump.

Calculate the "net height" by subtracting the standing reach height from the jump height. The best of three attempts is recorded.

Result interpretation

Go to the indicated website. Enter information (sex, population category, body weight and the peak vertical jump) in left column; Click "Calculate". Record the result.

MPrF-02C

Net Height

Sex

Population

Body Weight

Population Average

Score

Rating

Mean Power (kgm/sec)

The vertical jump height are categorized for various populations including children (ages 10-17), adults (ages 18-29), and world class athletes.

REFERENCE NORM: Adult norms based on data from the Fitness Institute of Texas, University of Texas at

Austin. Children's norms based on data from Texas Test 1973.

MPrF-02CGUIDELINES FOR MUSCLE PERFORMANCE TEST REPORT

The lab report is a full narration group report. Each member of the group must participate in writing the report and must be pointed out explicitly in the report.

The guidelines of the lab report:1. Text should typewritten, formatted as 12 point Times New Roman font size, and 1.15-

spaced. The page limit for the report is 20 pages (excluding cover and references). Please write clearly and concisely.

2. The report consists ofa. Introduction (max. 1 page):

i. What did you do?ii. Why did you do it?

[In this section, clearly state the test objectives. Describe in general the mechanism of muscle contraction and the importance of assessing muscle performance]

b. Literature Review (max. 6 pages): [Write down the supporting theories to the experiment, what results were expected from the experiment]

c. Materials and Methods (max. 3 pages):i. A brief outline or schematic of your experimental setup, and a reference to your

laboratory manual.ii. Specify any deviations from the protocol in the Laboratory Manual.

[Do not restate the protocol from the laboratory manual. Use this section to briefly summarize the methodology and to highlight any specific procedural changes.]

d. Results (max. 4 pages):i. Calculate descriptive statistics (mean and standard deviation) for the pooled class

data.ii. Present the calculated values (descriptive statistics) in an appropriate and

informative way (tables, figures and/or graphs), and in anticipation of the points that you will address in the discussion section of the report.

[Do not duplicate your reporting of data - that is, present the data in either tabular or graphical form, but not both.]

e. Discussion (max. 6 pages):i. Compare the findings with the expected results based on theory (that is, explain

the results in accordance with factors affecting muscle performance). ii. Note and discuss, as appropriate, any agreements and/or disagreements between

expected and observed findings.iii. In making comparisons, consideration should be given to the identification of

appropriate control groups (if any).iv. What is the conclusion(s)?

f. Reference:[Write down list of reference according to the Vancouver method (see Medical Journal of Indonesia)]