也要保持半分钟，这样反复交替练习20分钟。

Also want to maintain half minutes, practice 20 minutes alternately repeatedly so.

youdao

然后试着做些单臂与另一个手臂的交替练习，建设成为全程游泳的练习。

Then try a few single-arm strokes with each arm, building into full stroke swimming.

youdao

交替练习，需要使用投掷臂的练习与那些压力较小的练习交替，提供了一些保护，防止过度磨损和撕裂。

Alternating drills that emphasize heavy usage of the throwing arm with those that are less stressful provides some protection against excessive wear and tear.

youdao