I took Mg before, and stopped because it never did much..........now I am taking the Calcium and started with Mg again. I did this because I have been having rather bothersome runs of VT and SVT while on the treadmill , more since my tune up. I have also had a stomach bug, so my lytes might be off. Just wanted to say, I HAVE noticed a difference in just 3 days........yesterday I only had 2 runs in 1 hour, and only one to the point of slight dizziness. Thanks for the tip. The trouble was before........I would have the VT, a short run of normal beats, long run of VT, short run of sinus, VT again.............then fine for 5 minutes, then the cycle again, with occassional SVT..............arrrgh. Not that it matters, because my EF is normal now, but I don't want to fall and break my cheek implants. So thanks.... you did good....it's working. :)