句子：

Adding to a woman's increased dose of stress chemicals are her increased opportunities for stress.

这个倒装句是将现在分词短语"Adding to a woman's increased dose of stress chemicals“前置、谓语动词为"are"、主语是"her increased opportunities for stress"吗？

但是如果把这个句子恢复成正常结构：

her increased opportunities for stress are adding to a woman's increased dose of stress chemicals.

这里面的现在分词"adding to"感觉又像是和前面的are一起构成现在进行时态，这样的话谓语就应该是"are adding to"了，作为谓语一部分的"adding to"似乎是不能前置形成倒装句的，即应该是：

A woman's increased dose of stress chemicals are adding to  her increased opportunities for stress.

此处感觉不解，还请指点。