Why lift a heavy weight from the floor by flexing and then extending the knees rather than flexing at the hips and then lifting the trunk?

Question

Quizplus · Accepted Answer

Flexing and extending the knees creates a shorter resistance arm, which allows for a more efficient and effective transfer of force to lift the weight. Flexing at the hips and then lifting the trunk creates a longer lever, which requires more force to be applied to lift the same weight.

Why Lift a Heavy Weight from the Floor by Flexing