I laid off running for about three years. I mostly was doing cycling. Not competitive racing but riding a lot of century rides and other long endurance events. I was logging about 4,000 miles a year on the bike but I only really cycle about six months out of the year. This year once winter set in I started to go back to running. Here's the problem. Besides being very slow, my back is killing me after just a 5-10 minutes of running. It eases up quite a bit after I stop. I've never had this before and am wondering what is causing it. Any exercises that might help? It only bothers me when I am actually running. Doesn't affect me at all any other time.