Understand the Difficulty of Torque Situps: Expert Response

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Performing sit-ups with hands behind the head is more challenging than with arms extended forward due to the shift in center of mass and moment of inertia. When arms are positioned behind the head, the mass is further from the body's center, requiring more energy to lift the torso. This increased distance from the axis of rotation, which is at the hips, makes the movement more difficult. The change in body mechanics significantly impacts the effectiveness and effort needed for the exercise. Understanding these principles can help in optimizing workout techniques for better results.
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Can anyone help me with this question?

Why is it more difficult to do a sit-up with your hands behind your head than with your arms stretched out in front of you?
 
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hshphyss said:
Can anyone help me with this question?
Why is it more difficult to do a sit-up with your hands behind your head than with your arms stretched out in front of you?

I would guess it is because with your arms over your head, they are further from your bodies center of mass, meaning it would take more energy to sit up.
 
As Jordan_ indicated, with the arms extended forward, the moment of intertia is changed (decreased) as compared to putting hands behind one's head. Putting the hands behind the head moves the mass away from the axis of rotation, the hips.
 

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