Thanks for the reply. I guess I've been running for 4 years, but mostly in triathlon. I was a smoker from age 18-35. High school sport background in Tennis, Boxing and Wrestling. Ran one year of track in Jr high and one in high school. Ran anything from the 100 to the 300 intermediate hurdles, so I'm more of a natural sprinter. I'm a little in the muscular side for a distance runner. My 5k PR is 19:40, Half marathon 1:34(second year of running) marathon 3:42 in my first year of running, but haven't run one outside of an ironman since then. I've never focused on running enough to get decent at it, but I'd like to put in a 5 month focus before I get deep into the triathlon season. I'm 2.5 months into that period now and am at 45 miles. Thanks for any advice!