keep still.的keep在此是什么意思

keep still.的keep在此是什么意思 Swimming helps to keep her heart and lungs healthy and it is a good way to keep fit.swimming在此的用法是? 到底应该是keep health还是keep healthy呢?如果是keep health又哪来的keep healthy这种说法?如果是keep healthy那为什么我在“知道”里看到How to keep health?这种句子呢? keep keep keep keep keep keep keep Keep keep keep keep keep KEEP keep keep