1. This boost in reaction time after exercise training may occur because declines associated with getting old could actually stem from declines in physical condition.
    接受运动训练之后，人的反应速度会加快，这可能是因为与衰老有关的机能衰退实际上根源于体质下降。

2. I couldn´t stem the bleeding.
    我无法止住流血。