I started the C25K for the first time in Aug2014. I completed it and ran a 5k in Oct. I decided that I wanted to try to build to a 10k but I also wanted to increase my speed some. I restarted the C25K this time building some speed. I just completed it again and and into the first week of building to 10k. I've really enjoyed the movement and challenges through this. I've been having some calf muscle soreness since I've increased my speed though and am wondering if I need to slow down again and just go at it slow.