你说第一张图吧?那是发球

来源: 于 2013-04-03 14:17:56 [旧帖] [给我悄悄话] 本文已被阅读：次

it's about Kick serve vs regular serve. I assume you know what a kick serve is.

Full artical here:

http://twu.tennis-warehouse.com/learning_center/kickserve.php