I have been experiencing muscle cramps since I started e-cigs about 3 weeks ago. For me, they are at my lower back kidney area, lower rib cage, & sore shoulders and neck. If you're experiencing this too there is an excellent thread located at Health Issues or use the "Search ECF with Google" box at top of page for "muscle cramps". There does seem to be a connection to E-cigs, different opinions on what exactly causes it. Since I got new RIVA and real satisfying hits, I'm vaping less and the cramps have subsided. Before I was vaping all day just to try to get a satisfying hit so probably took in way too much nicotine or PG. Even with cramps, which I can experiment with my juice to find out what's causing it, it's still safer than cigs. I have COPD and I'm confident the e-cigs will save my life because I was totally unable to quit before now. So if you have some odd symptoms, switch juices, don't give up.