The chief function of the muscles of the back when one is erect is to resist gravity.

一个站立的人的肩肌的主要功能是抵抗重力。

youdao

This exercise will work the muscles of the lower back.

这样的运动可以锻炼腰部的肌肉。

《牛津词典》

To stand, you have to tense your leg muscles, and engage the muscles of your back and shoulders; while standing, you often shift from leg to leg.

要站起来，你必须使你腿上的肌肉拉紧，你背上和肩上的肌肉也要参与；站着的时候，你的腿常常会转来转去。

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This temporarily blocks signals that pass through the nerves to the muscles of the body and back to the brain.

VOA: special.2009.01.06

"By the time you are done with me, your back muscles are going to be in a heap of pain, " the colon went on.

WSJ: Book Excerpt: Confessions of a Surgeon

CTDs are musculoskeletal disorders involving damage to tendons, bones, muscles, and nerves of the hands, wrists, elbows, neck, and back.

CNN: Get comfortable -- computing ergonomics efforts pay off

The back of my throat went on tightening, and other muscles lower down my neck joined in, tugging at my lips, trying to stretch them over my teeth.

NEWYORKER: Hand on the Shoulder