Received my new Merrell Vapor Glove shoes yesterday afternoon. From previous experience, I know not to go out too hard or often in these minimalist shoes. Wasn't sure how far this run would be. 1 mile, 2 miles, I was going to go by feel. After a mile and a half I could feel the tightness in my calves so I cut the run at 2 miles; knowing not to push it too hard and risk injury. From a cardio standpoint I felt great. Could have kept going easily. The shoes are wonderful to run in, but I can feel the extra tightness in the calves. Will continue to run in my Asics and work in 1 to 2 runs a week in the Merrells until I can handle them full time.