Without regular exercise, his muscles began to languish.

### 解释 languish 是动词，由词根 langu-（来自拉丁语 languere，表示"虚弱、无力"）和后缀 -ish（表示"成为某种状态"）组成，意思是"变得虚弱无力"或"逐渐衰退"。在句中指肌肉因缺乏锻炼而变得松弛无力。