A worker bends over at the waist to pick up a load. The angle of flexion (w/vert

Question

A worker bends over at the waist to pick up a load. The angle of flexion (w/vertical) is 130 degrees and moment arm for the muscle force is 5cm. For the geometry shown: Calculate the muscle force, compression and shear on the L_4/L_5 joint Discuss the difference between the task load and the postural load and suggest way of reducing the task load. Note that the distances between ULs and COGs of the upper body and load are parallel to the body, but not the ground. Remember lo show you free body diagrams.

Explanation / Answer

solution:

1)angle of flexion is angle between two body parts,means angle between legs and chest is 130 degree,which means body inclined 130-90=40 degree to horizontal

2)forces along the body are

at cg

Fx1=F1sin40=-257.11 N

at L5

Fx2=F2sin40=-96.4181 N

this is total compression force on body

compression force at L4=Fx1+Fx2=-353.52 N

at L5 c.force=Fx2=-96.4131 N

3)forces perpendicular to body are

at cg

Fy1=F1cos40=306.41 N

at L5

Fy2=F2cos40=114.90 N

hence resultant force is shear force at L4

shear force=Fy1+Fy2=421.31 N

4)here muscle force all over the lengt is bending moment at L4

Ml4=0

Fy1*.4+Fy2*.6-muscle force*l=0

muscle force*l=191.504 Nm

5)taskload is load which we are going lift and posterul load is due to our body position,one way to reduced task load is to keep postrual load and task load opposite to each other .

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