Shoulders back, chest out.

扩肩，挺胸。

youdao

Keep the chin up, butt back, and chest out, but don't over-exaggerate22 or you will look like an over-eager porpoise23 my first mistake.

时刻高抬下巴，提臀，挺胸，但不要太过夸张，否则你会看起来像只过于急切的小海豚(这是我犯的第一个错误)。

youdao

With swift, vigorous propulsion of hands and feet, he lifted his shoulders and half his chest out of water.This was to gain impetus for the descent.

他激烈地迅速地划动手脚，把肩头和半个胸膛露出了水面，这是为了聚集下沉的冲力。

youdao

Poor Billy! A bullet came out of the sky one day and tore a great hole in Billy's chest.

VOA: special.2009.12.12

Oh, great. So, that is her daughter, Sam that you see strapped to the chest, and Dr. Patti Christie helping us out here.

首先，我们要有单层的金原子，看看Drennen教授，能不能帮我们一下。

麻省理工公开课 - 化学原理课程节选

But the rest of the state has its head up and its chest out.

ECONOMIST: The chief minister wins again

Mr. LU JUNG YONG (Coach): (Through translator) Don't keep your chest out.

NPR: Pingpong: A Chinese Obsession

You either go into a shell or you puff your chest out, take it on the chin and get on with it.

BBC: SPORT | Football | Internationals | Gilberto backs Gerrard & Lampard