[Idiom] if I so much as step on bubble wrap

[myenglishsucks]

I read this on Quora, a website in which you can ask and answer questions. The writer of the following sentence thinks that walking flinchlessly when there is an explosion behind you is illogical, (he was talking about action movies).
''[...]Is it even physically possible to be this immune to a massive explosion? They would need to do a lot of takes if I was one of their actors. Because I hit the ground if I so much as step on bubble wrap.''
Could you rephrase the bold sentence? I'm not sure what he meant by any of that, especially the expression ''if I so much as''. And yes, I have already tried looking it up but I am still clueless. By the way, I'm new to this Forum so excuse me if I've broken any rules.
Thanks in advance.

 

[emsr2d2]

Welcome to the forum. :hi:

It means "Even if I do something as insignificant as stepping on some bubble wrap, the sound of the bubble wrap popping makes me jump/flinch/dive to the floor".