1. But the ratio is even greater among active women, affecting up to 80 percent of female endurance athletes.
    而这一比例在积极锻炼的妇女中数值更高，女耐力运动员中缺铁的则高达80%。

2. He came to the end of his endurance.
    他已忍无可忍了。

3. Sports medicine experts have observed for years that endurance athletes, particularly females, frequently have iron deficiencies.
    运动医学专家经过多年的观察，发现耐力运动员，特别是女性，经常会缺铁。

4. Some iron is lost in sweat, and, for unknown reasons, intense endurance exercise is sometimes associated with bleeding of the digestive system.
    有些铁离子随汗液流失。另外，由于某些未知的原因，高强度的耐力运动有时是与消化系统内出血联系在一起的。