as required 的完整形式是什么

Do exerciseas often as required.

请问这里的asrequired 是由什么省略来的？它的完整形式是什么？谢谢！

▲赞同前面两位老师的解答！我感觉依据require这个动词的搭配特征，as required可以有不止一种补全方法。

1. 依据 require sb to do sth 这一搭配，大家可以将它作如下补全：

Do exercise as often as required .

2. 依据 require that-clause 与 it is required that-clause 这一搭配，大家可以将它作如下补全：

Do exercise as often as required ).

▲类似的使用方法再如as expected。如：

He didn’t do his work as well as expected.

补全方法1、

He didn’t do his work as well as expected .

补全方法2、

He didn’t do his work as well as expected .