Which biomechanical principle explains why bending at the waist to lift a load significantly increases lumbar disc compression compared to bending at the knees?
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A
The moment arm of the load is longer when the spine is flexed forward
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B
The load weighs more when held away from the body's center of gravity
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C
Knee flexion reduces gravitational force on the load
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D
Hip extensors are weaker than lumbar extensors