I've had Vibram Fivefingers or a while now, but it's been several months since I've seriously worn them and ran with them for any distance. I was doing a lot of martial arts last summer and fall, and they were perfect for training outside. I've run more in this last month than I have my whole life, but it has been with regular running shoes.
After some researching it seemed to me like Vibrams may be a good choice for running in an obstacle course race, which has been my secondary fitness goal lately (running my first 5K being my primary). They can handle being wet, can give good traction for climbing, and I have a pair made for trails that protects against stones and other sharp stuff. So last week I wore them for a run, about 3 miles or so. This was way too long of a run considering how long I had gone without wearing them. You land differently on your feet running with this type of shoes, and it puts more stress on your calves while reducing some stress on your knees. The trade off is good in the long term, but in the short term you really put a lot of unusual strain on the calves while you build up those muscles.
So for the past 5 days or so my calves have constantly ached and I have been unable to run, and can barely walk when I wake up in the morning. Today I felt a little better and ran with some regular New Balances but my left calf started hurting bad about halfway up the first hill. I now have about 6 days until my first 5K and I'm nursing this injury and probably can't do much else but rest the next few days.
Live and learn, right? After the 5K (which I will be wearing regular shoes for), I will try to ease into the Vibrams again. I am not signed up for any OCR's at the moment so I don't need to rush into them... I think a slower transition will be helpful.