Signed up for my first half marathon around a month ago & since then been slowly but surely building up my runs every few days, going from complete beginner to around 4 miles. Had to stop a couple times last week due to my calfs feeling tight and sore, did a bit of research and a few websites suggested getting some extra magnesium in the body in the form of pre-workout. All I can say is this stuff is like rocket fuel resulting in me jogging about for a good 45 minutes last night. Anyone else use supplements before/after a run?