crawl backstroke

While other styles like the breaststroke, front crawl, or backstroke can be swum easily even by beginners, the butterfly is a more difficult stroke that requires good technique to be feasible.

初学者也许能很容易地掌握蛙泳、自由泳或仰泳，但蝶泳却难得多，对游泳者的技术要求很高。

In dozens of experiments, scientists have shown that mixing related skills in a single practice session-new material and old, scales and improvisation, crawl and backstroke-seems to sharpen each skill more quickly than if practiced repeatedly on its own.

科学家在数十项实验中证明，相比于重复地练习某种单一技能，将相关的技能——如新内容和老内容、音阶和即兴演奏、自由泳和仰泳——融入同一个练习环节中，似乎能更快地增强其中涉及的各种技能。

The principal swimming strokes are the crawl, backstroke, breaststroke and butterfly.

主要游泳姿式有爬泳、仰泳、蛙泳和蝶泳。

Holding the body on the side produces no more or no less drag resistance than holding it prone in crawl or backstroke.

保持身体在一侧的姿势产生的拖曳阻力相对保持身体水平的姿势来说是一样的，不多也不少。

Champion swimmers do not illustrate swimming in an exaggerated long, thin, on the side position in either crawl or backstroke.

游泳冠军们不会在爬泳和仰泳的一侧位置时使用夸张的长的，细的身体姿势。