Use a static analysis to compare a leg-lifting technique with a back-lifting tec
ID: 1502834 • Letter: U
Question
Use a static analysis to compare a leg-lifting technique with a back-lifting technique when lifting a force platform from the floor. In both cases, the upper body weight is 460 N, and the force platform is 270 N. The upper body moment arm from the L5/S1 disc is 0.100 m for the leg-lift and 0.170 m for the back-lift. The force platform moment arm from the L5/S1 disc is 0.250 m for the leg-lift and 0.430 m for the back-lift. The surface of the sacrum is tilted 30° from the horizontal during the leg-lift and 40° during the back-lift. The erector spinae moment arm is 0.060 m.
1) What is the force that is developed in the erector spinae muscles for each lifting technique?
A. 730 N leg-lift, 730 N back-lift
B. 1125 N leg-lift, 1935 N back-lift
C. 1892 N leg-lift, 3238 N back-lift
D. 2367 N leg-lift, 4062 N back-lift
2) What is the compressive reaction force due to the weight above the L5/S1 disc for each lifting technique?
A. 234 N leg-lift, 207 N back-lift
B. 365 N leg-lift, 469 N back-lift
C. 632 N leg-lift, 559 N back-lift
D. 730 N leg-lift, 730 N back-lift
3) What is the total compressive force on the L5/S1 disc for each lifting technique?
A. 1359 N leg-lift, 2142 N back-lift
B. 1460 N leg-lift, 1460 N back-lift
C. 2524 N leg-lift, 3797 N back-lift
D. 2732 N leg-lift, 4531 N back-lift
4) What is the shear reaction force on the L5/S1 disc for each lifting technique?
A. 135 N leg-lift, 174 N back-lift
B. 365 N leg-lift, 469 N back-lift
C. 632 N leg-lift, 559 N back-lift
D. 730 N leg-lift, 730 N back-lift
5) Which loading situation contributes most to the external torque about the L5/S1?
A. Body weight during the back-lifting technique
B. Body weight during the leg-lifting technique
C. Force platform during the back-lifting technique
D. Force platform during the leg-lifting technique
Explanation / Answer
1) What is the force that is developed in the erector spinae muscles for each lifting technique?
C. 1892 N leg-lift, 3238 N back-lift
2) What is the compressive reaction force due to the weight above the L5/S1 disc for each lifting technique?
D. 730 N leg-lift, 730 N back-lift
3) What is the total compressive force on the L5/S1 disc for each lifting technique?
A. 1359 N leg-lift, 2142 N back-lift
4) What is the shear reaction force on the L5/S1 disc for each lifting technique?
A. 135 N leg-lift, 174 N back-lift
5) Which loading situation contributes most to the external torque about the L5/S1?
C. Force platform during the back-lifting technique
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