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Chapter 12: Problem 3

The best way to lift a heavy weight is to squat with your back vertical, rather than to lean over. Why?

Short Answer

Expert verified
Squatting with a vertical back while lifting a heavy weight is recommended as it reduces the torque that needs to be counteracted by the lower back muscles, thus minimizing the strain.

Step by step solution

01

Understand the problem

Considering a person lifting a heavy weight in two different postures - one where they are leaning over and one where they maintain a vertical back posture. The task is to explain why the latter is recommended.
02

Analyzing the forces with a leaning posture

When leaning over to pick up a weight, there is a larger torque that needs to be counteracted by the muscles in the lower back. This is because torque, or turning force, is the product of the force (weight) and the distance (height difference when leaning over) between the force and the pivot point (usually the lower back or the waist). When leaning over, this distance and therefore the torque is increased, putting a strain on the lower back.
03

Analyzing the forces in a vertical posture

In contrast, when lifting with a squatting posture with your back vertical, the distance between the heavy weight and your lower back is reduced, leading to a smaller torque that needs to be counteracted. This reduces the strain on your lower back.
04

Conclusion

Therefore, it is better to lift a heavy weight with a squatting posture, keeping your back vertical to minimise the torque and therefore the strain on your lower back.

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