The concert experience for any band is just something awesome. There are many factors which can transform the crowd into a sea of raw energy. Certainly if you are surrounded by a bunch of bulky or large people it could be rough, but don't let that get you down you need to wonder why it gets so rowdy in the first place.
Mostly there is this huge wave of adrenaline that rushes over everyone so whether your strong or not if the adrenaline takes you over and you don't have issues with personal space you may find that even the smallest fans become more energized and peppy, suddenly the smallest fans start holding their own. I mean it helps if you are in shape, but I would say loosing yourself to the music and adrenaline is also a majour factor for why it gets rough and how you can deal with it. I mean science has shown athletes who are an an adrenaline high can play sports on broken legs and barely feel it same with dogs, and same with hardcore Muse fans lol... not that anything like that will happen though.