I was required to hold out my arms and flex my pectorals.

我被要求伸展手臂，收紧胸肌。

柯林斯例句

His dorsal fin was down and his huge pectorals were spread wide.

它的脊鳍朝下耷拉着,巨大的胸鳍大张着.

英汉文学 - 老人与海