Unfit: of a person 人 not in good physical condition; not fit, because you have not taken exercise 健康状况欠佳;身体状态差
The captain is still unfit and will miss tonight's game. 队长身体欠佳,将不会出席今晚的比赛.

Mire: an area of deep mud 泥潭;泥沼
The wheels sank deeper into the mire. 轮子在泥潭中陷得更深了.
My name had been dragged through the mire(= my reputation was ruined). 我的名声受到了玷污.
The government was sinking deeper and deeper into the mire(= getting further into a difficult situation). 政府在泥潭中越陷越深.

Stretch: an act of stretching out your limbs or your body and tightening the muscles; the state of being stretched 伸展;舒展
We got out of the car and had a good stretch. 我们下车好好舒展了一下身体.
Only do these more difficult stretches when you are warmed up. 要做了准备活动以后再做这些较难的伸展运动.
Stay in this position and feel the stretch in your legs. 保持这个姿势,体会腿部绷紧的感觉.

Stroll: a slow relaxed walk 散步;溜达;闲逛
We went for a stroll in the park. 我们去公园散了散步.