This is called a kegel exercise and it can be done to strengthen the pelvic floor.

这被称为凯格尔运动，能够锻炼盆底肌。

This is the reason that it's possible to stop urine mid-stream by tightening up that muscle, which is called doing kegel exercises.

这就是为什么收缩外括约肌可以中断排尿过程，即所谓的Kegel运动。