Laboratory Experiments: Measurement and Interpretation of Muscle Force Vectors, Moments, and Power...

Laboratory Experiments: Measurement and Interpretation of

Muscle Force Vectors, Moments, and Power for Knee Flexion

Experiments 2 and 3

• Biomechanics of Maximum Isometric

Knee Flexion Torque for Various Knee Joint Angles

•Biomechanics of Maximum Isokinetic

Knee Flexion Torque for Various Knee Joint Angles and Angular Velocities

Experiments 2 and 3 – Measured and Calculated Isometric Parameters

Knee Joint Angle

(Thata 2) (deg)

Angle of Attachment of Muscle to Shank (Theta 1)

(deg)

Muscle Length (OI)

(m)

Muscle Moment

Arm (m)

Torque Applied to Cybex Arm

(Nm)

Joint Turning

Force (Fx) (N)

Force Applied to Cybex Arm

(Fc) (N)

Joint Compres-sion Force

(Fy) (N)

Force of Muscle

Contrac-tion (F1)

(N)Power

(Nm/sec)180 3.41 0.4207 0.00297 165 13.64 0.4185 0.01179 103.14 2062.8 343.8 6996.21031 7199.31852 0150 30 0.4133 0.025 102.86 2057.2 342.866667 3563.16485 4114.39127 0135 43.5 0.4057 0.0344 101.69 2033.8 338.966667 2143.25624 2954.63869 0120 57.4 0.3953 0.04212 76.06 1521.2 253.533333 976.751287 1807.78663 0105 71.5 0.3836 0.0474 69.71 1394.2 232.366667 466.508941 1470.1783 090 86.2 0.3708 0.0499 64.63 1292.6 215.433333 85.8204016 1295.44583 0

Maximum Isometric (0 deg/sec)

2a. Neatly plot on one sheet of graph paper Fx versus 2, Fy versus 2, and

F1 versus 2 for maximum isometric contractions for the knee

joint angles of165, 150, 135, 120, 105,

and 90. Distinguish between the three lines.

What interpretation did you make of this data?

Force vs Knee Angle - Isometric

0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N

)

Fx

Fy

F1

• A relatively small proportion of muscle contraction goes into turning the joint.

• Most of the force of muscle contraction goes into compressing the joint, especially when its mechanical advantage is poor.


0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N

)

Fx

Fy

F1

• When the muscle is at its greatest length (largest knee joint angle), it exerted substantially greater contractile force.

• The combination of muscle length and mechanical advantage resulted in a relatively constant turning component (Fx) over the range of knee joint positions.


0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N

)

Fx

Fy

F1

Experiments 2 and 3 – Measured and Calculated Isokinetic Parameters

Knee Joint Angle

(Thata 2) (deg)

Angle of Attachme

nt of Muscle to

Shank (Theta 1)

(deg)

Muscle Length

(OI) (m)

Muscle Moment

Arm (m)

Torque Applied to

Cybex Arm (Nm)

Joint Turning

Force (Fx) (N)

Force Applied to

Cybex Arm (Fc)

(N)

Joint Compres-sion Force

(Fy) (N)

Force of Muscle

Contrac-tion (F1)

(N)Power

(Nm/sec)180 3.41 0.4207 0.00297165 13.64 0.4185 0.01179 90.17 1803.4 300.56667 6116.427 6293.9941 23.606506150 30 0.4133 0.025 86.72 1734.4 289.06667 3004.0604 3468.7926 22.703296135 43.5 0.4057 0.0344 80.65 1613 268.83333 1699.8094 2343.3141 21.11417120 57.4 0.3953 0.04212 74.33 1486.6 247.76667 954.53488 1766.6682 19.459594105 71.5 0.3836 0.0474 66.54 1330.8 221.8 445.29486 1403.3233 17.42017290 86.2 0.3708 0.0499 65.5 1310 218.33333 86.975651 1312.8841 17.1479

Maximum Isokinetic (15 deg/sec = 0.2618 rad/sec)


(continued)

Knee Joint Angle

(Thata 2) (deg)

Angle of Attachm

ent of Muscle

to Shank (Theta

1) (deg)

Muscle Length

(OI) (m)

Muscle Moment

Arm (m)

Torque Applie

d to Cybex Arm (Nm)

Joint Turning Force (Fx) (N)

Force Applied

to Cybex Arm (Fc)

(N)

Joint Compres-

sion Force (Fy) (N)

Force of Muscle

Contrac-tion (F1)

(N)Power

(Nm/sec)180 3.41 0.4207 0.00297165 13.64 0.4185 0.01179 75.19 1503.8 250.6333 5100.301 5248.37 78.739150 30 0.4133 0.025 79.8 1596 266 2764.345 3191.99 83.5666135 43.5 0.4057 0.0344 87.25 1745 290.8333 1838.913 2535.08 91.3682120 57.4 0.3953 0.04212 74.33 1486.6 247.7667 954.5349 1766.67 77.8384105 71.5 0.3836 0.0474 70 1400 233.3333 468.4497 1476.29 73.30490 86.2 0.3708 0.0499 64.05 1281 213.5 85.05024 1283.82 67.0732


Experiments 2 and 3 – Measured and Calculated Isometric Parameters

(continued)

Knee Joint Angle

(Theta 2) (deg)

Angle of Attachme

nt of Muscle to

Shank (Theta 1)

(deg)

Muscle Length

(OI) (m)

Muscle Moment Arm (m)

Torque

Applied to

Cybex Arm (Nm)


Force Applied

to Cybex Arm (Fc)

(N)

Joint Compres-

sion Force (Fy) (N)

Force of Muscle

Contrac-tion (F1)

(N)Power

(Nm/sec)180 3.41 0.4207 0.00297165 13.64 0.4185 0.01179 36.59 731.8 121.9667 2481.979 2554.034 57.47557150 30 0.4133 0.025 65.98 1319.6 219.9333 2285.608 2639.194 103.6414135 43.5 0.4057 0.0344 72.02 1440.4 240.0667 1517.92 2092.566 113.129120 57.4 0.3953 0.04212 76.35 1527 254.5 980.4754 1814.679 119.9306105 71.5 0.3836 0.0474 69.14 1382.8 230.4667 462.6944 1458.157 108.605190 86.2 0.3708 0.0499 58.58 1171.6 195.2667 77.78677 1174.179 92.01746



(continued)

Knee Joint Angle

(Thata 2) (deg)

Angle of Attachme

nt of Muscle to

Shank (Theta 1)

(deg)

Muscle Length

(OI) (m)


Torque Applie

d to Cybex Arm (Nm)


Force Applied

to Cybex Arm (Fc)

(N)

Joint Compres-

sion Force (Fy) (N)

Force of Muscle

Contrac-tion (F1)

(N)

Power (Nm/sec

)180 3.41 0.4207 0.00297165 13.64 0.4185 0.01179 53 1060 176.6667 3595.105 3699.48 111.003150 30 0.4133 0.025 63.96 1279.2 213.2 2215.633 2558.39 133.958135 43.5 0.4057 0.0344 67.4 1348 224.6667 1420.547 1958.33 141.163120 57.4 0.3953 0.04212 63.09 1261.8 210.3 810.1925 1499.52 132.136105 71.5 0.3836 0.0474 65.1 1302 217 435.6582 1372.95 136.34590 86.2 0.3708 0.0499 30.35 607 101.1667 40.30093 608.336 63.565



(continued)

Knee Joint Angle

(Thata 2) (deg)

Angle of Attachm

ent of Muscle

to Shank (Theta 1)

(deg)

Muscle Length

(OI) (m)


Torque Applie

d to Cybex Arm (Nm)


Force Applied to

Cybex Arm (Fc)

(N)

Joint Compres-

sion Force (Fy) (N)

Force of Muscle

Contrac-tion (F1)

(N)

Power (Nm/sec

)180 3.41 0.4207 0.00297165 13.64 0.4185 0.01179 63.38 1267.6 211.26667 4299.203 4424.01 165.929150 30 0.4133 0.025 66.84 1336.8 222.8 2315.399 2673.59 174.987135 43.5 0.4057 0.0344 68.56 1371.2 228.53333 1444.996 1992.03 179.49120 57.4 0.3953 0.04212 65.68 1313.6 218.93333 843.4529 1561.08 171.95105 71.5 0.3836 0.0474 63.08 1261.6 210.26667 422.1401 1330.35 165.14390 86.2 0.3708 0.0499 54.26 1085.2 180.86667 72.05036 1087.59 142.053

Maximum Isokinetic (150 deg/sec = 2.6180)


(continued)

Knee Joint Angle

(Thata 2) (deg)

Angle of Attachm

ent of Muscle

to Shank (Theta

1) (deg)

Muscle Length

(OI) (m)


Torque Applie

d to Cybex Arm (Nm)


Force Applied

to Cybex Arm (Fc)

(N)

Joint Compres-

sion Force (Fy) (N)

Force of Muscle

Contrac-tion (F1)

(N)Power

(Nm/sec)180 3.41 0.4207 0.00297165 13.64 0.4185 0.01179 37.16 743.2 123.8667 2520.644 2593.82 116.742150 30 0.4133 0.025 54.16 1083.2 180.5333 1876.152 2166.4 170.149135 43.5 0.4057 0.0344 60.2 1204 200.6667 1268.798 1749.13 189.124120 57.4 0.3953 0.04212 62.52 1250.4 208.4 802.8726 1485.97 196.413105 71.5 0.3836 0.0474 60.2 1204 200.6667 402.8667 1269.61 189.12490 86.2 0.3708 0.0499 49.36 987.2 164.5333 65.54379 989.373 155.069


2b. Neatly plot on one sheet of graph paper Fx versus 2, Fy versus 2, and F1 versus 2 for maximum isokinetic contractions for

the knee joint angles of 165, 150, 135, 120, 105, and 90 for the three angular

velocities. Use the same scale for this plot as was used in 2a. For the nine lines,

distinguish between the three parameters and three angular velocities.

For 2a. and 2b., explain the relationships that exist between knee joint angle (2) and the force

of muscle contraction (F1), joint turning component (Fx) of muscular contraction, and joint compressive component (Fy) of muscular

contraction. Are these relationships similar between the isometric and isokinetic

contractions? Explain. Is there a pattern, going from the isometric contractions to faster and

faster isokinetic contractions? In other words, is there a relationship between

angular velocity and the three force vectors? Explain.


Force vs Knee Angle - Isokinetic

0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N)

Fx - 15 deg/sec

Fy - 15 deg/sec

F1 - 15 deg/sec

Fx - 90 deg/sec

Fy - 90 deg/sec

F1 - 90 deg/sec

Fx - 180 deg/sec

Fy - 180 deg/sec

F1 - 180 deg/sec

• The same pattern existed in the isokinetic contractions as was evident in the isometric contractions (see isometric graph).

• A similar pattern is evident among these angular velocities.


0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N)

Fx - 15 deg/sec

Fy - 15 deg/sec

F1 - 15 deg/sec

Fx - 90 deg/sec

Fy - 90 deg/sec

F1 - 90 deg/sec

Fx - 180 deg/sec

Fy - 180 deg/sec

F1 - 180 deg/sec

• An inverse relationship between force of isokinetic contraction and angular velocity was expected.


0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N)

Fx - 15 deg/sec

Fy - 15 deg/sec

F1 - 15 deg/sec

Fx - 90 deg/sec

Fy - 90 deg/sec

F1 - 90 deg/sec

Fx - 180 deg/sec

Fy - 180 deg/sec

F1 - 180 deg/sec


Force vs Knee Angle

0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N)

Fx - 60 deg/sed

Fy - 60 deg/sec

F1 - 60 deg/sec

Fx - 120 deg/sec

Fy - 120 deg/sec

F1 - 120 deg/sec

Fx - 150 deg/sec

Fy - 150 deg/sec

F1 - 150 deg/sec

• The same pattern existed in the isokinetic contractions as was evident in the isometric contractions (see isometric graph).

• A similar pattern is evident among these angular velocities.

Force vs Knee Angle

0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N)

Fx - 60 deg/sed

Fy - 60 deg/sec

F1 - 60 deg/sec

Fx - 120 deg/sec

Fy - 120 deg/sec

F1 - 120 deg/sec

Fx - 150 deg/sec

Fy - 150 deg/sec

F1 - 150 deg/sec

• An inverse relationship between force of isokinetic contraction and angular velocity was expected. This was evident for these angular velocities.

Force vs Knee Angle

0

1000

2000

3000

4000

5000

6000

7000

8000

180 165 150 135 120 105 90

Knee Angle (deg)

Fo

rce

(N)

Fx - 60 deg/sed

Fy - 60 deg/sec

F1 - 60 deg/sec

Fx - 120 deg/sec

Fy - 120 deg/sec

F1 - 120 deg/sec

Fx - 150 deg/sec

Fy - 150 deg/sec

F1 - 150 deg/sec

3. Neatly plot on one sheet of graph paper the force of muscle

contraction (F1) versus muscle length (OI) for the isometric and

three isokinetic contractions. Distinguish between the four lines.

Can muscle force-velocity and length-tension relationships

justify these results? Explain.


Maximum Force of Hamstrings vs Muscle Length

0

1000

2000

3000

4000

5000

6000

7000

8000

0.37 0.375 0.38 0.385 0.39 0.395 0.4 0.405 0.41 0.415 0.42

Muscle Length (m)

Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

• A dynamic relationship existed between muscle length and its ability to exert maximum contractile force for all angular velocities tested.


0

1000

2000

3000

4000

5000

6000

7000

8000

0.37 0.375 0.38 0.385 0.39 0.395 0.4 0.405 0.41 0.415 0.42

Muscle Length (m)

Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

• As muscle length increased, there was an increase in its ability to exert force for all angular velocities. This relationship was relatively constant between 0.37 and 0.4 meters, but appeared curvilinear and increased substantially after achieving a muscle length of 0.4 meters.


0

1000

2000

3000

4000

5000

6000

7000

8000

0.37 0.375 0.38 0.385 0.39 0.395 0.4 0.405 0.41 0.415 0.42

Muscle Length (m)

Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

• The dynamic relationship between muscle length and its ability to exert maximum force of contraction is likely to be related to the a) overlap of actin and myosin myofilaments in the sarcomeres and b) series elastic component of skeletal muscle when length is greater than “resting” length.


0

1000

2000

3000

4000

5000

6000

7000

8000

0.37 0.375 0.38 0.385 0.39 0.395 0.4 0.405 0.41 0.415 0.42

Muscle Length (m)

Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

• Even though the isokinetic dynamometer maintained a constant angular velocity (as opposed to what typically is the case in an isotonic contraction) the following relationships were evident:

1. Force-velocity: With increased velocity there was a general trend for the knee joint flexors to be able to exert a decreased maximum force of contraction. This is also typical of what is seen in maximum isotonic contractions.


0

1000

2000

3000

4000

5000

6000

7000

8000

0.37 0.375 0.38 0.385 0.39 0.395 0.4 0.405 0.41 0.415 0.42

Muscle Length (m)

Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

• Even though the isokinetic dynamometer maintained a constant angular velocity (as opposed to what typically is the case in an isotonic contraction) the following relationships were evident:

2. Length-tension: A curvilinear relationship between maximum force of contraction and muscle length was evident. This is somewhat similar to what is typical at the muscle fiber level in which maximum force of contraction is dependent on the interaction between the overlap of the actin and myosin myofilaments and the tension associated with theseries and parallel elastic components


0

1000

2000

3000

4000

5000

6000

7000

8000

0.37 0.375 0.38 0.385 0.39 0.395 0.4 0.405 0.41 0.415 0.42

Muscle Length (m)

Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

4. Neatly plot on one sheet of graph paper the mechanical advantage (moment arm) of

the hamstrings to the knee joint center versus F1 for the isometric and isokinetic contractions for the knee joint angles of

165, 150, 135, 120, 105, and 90. Distinguish between the four lines.

Is there an inverse relationship between mechanical advantage and F1?

Explain.


Maximum Force of Hamstring Contraction vs Muscle Moment Arm

0

1000

2000

3000

4000

5000

6000

7000

8000

0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055


Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

• For all angular velocities (including the isometric condition), there was an inverse relationship between muscle moment arm and the muscle’s ability to exert maximum force of contraction.

Maximum Force of Hamstring Contraction vs Muscle Moment Arm

0

1000

2000

3000

4000

5000

6000

7000

8000

0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055


Fo

rce

(N)

F1 - Isometric

F1 - 15 deg/sec

F1 - 60 deg/sec

F1 - 90 deg/sec

F1 - 120 deg/sec

F1 - 150 deg/sec

F1 - 180 deg/sec

5. Neatly plot on one sheet of graph paper the mechanical advantage

(moment arm) of the hamstrings to the knee joint center versus and the muscle length (OI) of the hamstring muscles.

What is the relationship between mechanical advantage and

hamstring length? Explain.


Hamstring Moment Arm vs Muscle Length

0.37

0.38

0.39

0.4

0.41

0.42

0.43

0 0.01 0.02 0.03 0.04 0.05 0.06


Mu

scle

Len

gth

(m

)

• A curvilinear relationship existed between muscle length and muscle moment arm.

• As the muscle moment arm increased, the muscle length decreased.


0.37

0.38

0.39

0.4

0.41

0.42

0.43

0 0.01 0.02 0.03 0.04 0.05 0.06


Mu

scle

Len

gth

(m

)

• There appears to a compensatory mechanism in place. The mechanical advantage associated with a longer muscle moment arms is detracted by the loss in ability of the muscle to exert force due to decreases in its length. The opposite is also evident.


0.37

0.38

0.39

0.4

0.41

0.42

0.43

0 0.01 0.02 0.03 0.04 0.05 0.06


Mu

scle

Len

gth

(m

)

6. Neatly plot on one sheet of graph paper [(Fx)(AI)] versus 2 and [(Fc)(AC)] versus 2 for

the isokinetic contractions of 30/second [(/6) (radians/second)] for the knee joint angles of 165, 150, 135, 120, 105, and 90. Note that clockwise

moments about the knee joint center (A) are negative and counterclockwise moments are positive.

Distinguish between the two lines. An isokinetic dynamometer is said to provide “accommodating resistance.” Explain this relationship in regard to

constant angular velocity.


Isokinetic Torque vs Knee Angle

-100

-80

-60

-40

-20

0

20

40

60

80

100

180 165 150 135 120 105 90

Knee Angle (deg)

To

rqu

e (N

m)

(Fx)(AI) -15 deg/sec

(Fc)(AC) -15 deg/sec

(Fx)(AI) - 60 deg/sec

(Fc)(AC) - 60 deg/sec


(Fc)(AC) = 90 deg/sec







• For all angular velocities, the torque experienced by the arm of the isokinetic dynamometer was equal and opposite to the torque experienced by the subject’s shank. This is to be expected since the angular velocity of the isokinetic dynamometer is constant for all settings.

Isokinetic Torque vs Knee Angle

-100

-80

-60

-40

-20

0

20

40

60

80

100

180 165 150 135 120 105 90

Knee Angle (deg)

To

rqu

e (N

m)

(Fx)(AI) -15 deg/sec

(Fc)(AC) -15 deg/sec




(Fc)(AC) = 90 deg/sec







7. Neatly plot on one sheet of graph paper power versus angular velocity for the three isokinetic

contraction conditions for the knee joint angles of 165, 150, 135, 120, 105, and 90.

What relationship exists between power and angular velocity? Explain. What relationship exists between maximum power in each of the three isokinetic contraction conditions and the

joint angle at which it occurred? What are plausible explanations for this relationship?


Power vs Angular Velocity for Selected Knee Angles

0

30

60

90

120

150

180

210

180 165 150 135 120 105 90

Knee Angle (deg)

Po

wer

(N

m/s

ec)

15 deg/sec

60 deg/sec

90 deg/sec

120 deg/sec

150 deg/sec

180 deg/sec

• Power is the product of torque and angular velocity.

• It was previously interpreted that there was a general inverse relationship between angular velocity and the ability of muscle to generate maximum torque.


0

30

60

90

120

150

180

210

180 165 150 135 120 105 90

Knee Angle (deg)

Po

wer

(N

m/s

ec)

15 deg/sec

60 deg/sec

90 deg/sec

120 deg/sec

150 deg/sec

180 deg/sec

• A direct relationship between the muscle’s ability to generate power and angular velocity is evident.

• Of the two factors in determining power (torque and angular velocity), angular velocity appears to dominate.


0

30

60

90

120

150

180

210

180 165 150 135 120 105 90

Knee Angle (deg)

Po

wer

(N

m/s

ec)

15 deg/sec

60 deg/sec

90 deg/sec

120 deg/sec

150 deg/sec

180 deg/sec

8. What effects could internal anatomical differences in the locations of muscle

origins and insertions and bone (lever) lengths have on internally measured forces and torques? In other words,

what effects would changes in AI, AB, and OB have on internally measured forces and torques? How would these effects manifest themselves in external

measures of forces and torques?(See next slide for model figure.)

Definition of VariablesF1 – maximum force of hamstring contraction

Fc – maximum force applied at pad on mechanical arm

Fx –vector component of F1 perpendicular to rigid shaft of

shank; turning component of F1 at collective insertion (I)

of hamstringsFy – vector component of F1 parallel to rigid shaft of shank;

joint compressive component of F1 at collective

insertion (I) of hamstrings1 – angle between shaft of shank and F1 at I

2 – angle at knee joint center (A) formed by shafts

of the thigh and shankAI – distance between collective insertion of hamstrings (I)

and knee joint center (A); AI = _______ metersAC – distance from center of cuff to knee joint center (A);

AC = _______ metersAB – horizontal distance from knee joint center (A) to

a point B located directly above the collective origin(O) of the hamstrings; AB = _______ meters

OI – hamstring muscle lengthOB – distance from O to B; OB = _______ metersOP – distance from O to point P on shaft of shank, OP is

parallel to ABAS – perpendicular line from A to OAM – a line from point A that intersects OI, forming a right angle; moment arm of F1 (not drawn on figure)

Influence of

Changes in AI,

AB, and OB?

Other

Changes?

9. Several assumptions have been provided about this Hypothetical Model. List at least five additional assumptions

which cause this model to be hypothetical as opposed to an actual

model. For each of these assumptions, conjecture as to its potential influence on the results of the experiment (i.e.,

major or minor) and why you think this way.

Additional Assumptions

1. Two-dimensional versus three-dimensional model

2. Use of cadaver data

3. Other?

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Laboratory Experiments: Measurement and Interpretation of Muscle Force Vectors, Moments, and Power...

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