Final answer:
The correct phrase is 'the greater the lifting action,' referring to the increase in force on the back from lifting heavier volumes. Proper lifting technique is important to minimize this force, as improper lifting can exert a force on the spine that is 5.6 times greater than with a correct posture.
Step-by-step explanation:
The student's question appears to involve the principles of proper lifting technique and how volume, likely referring to the volume of a load, affects the lifting action on the human body, particularly the back. The correct word to complete the sentence 'The higher the volume, the greater the lifting action' could be used to express that heavier loads generally result in greater forces acting on the body.
According to the provided reference, when a person lifts improperly, such as with a rounded back, the force on the spine is about 5.6 times greater than it would be with proper lifting technique. Proper lifting technique entails keeping the back erect and utilizing the strength in the legs to lift, which significantly reduces the forces exerted on the spine. As such, proper lifting can create forces that are 5.6 times smaller in the back compared to improper lifting methods.