Ok so 5 weeks ago I started c25k. I'm not the fittest but used to cycle to work! I set an ambitious goal to complete a duathalon in 12 weeks! 7 weeks to go now. I've cut down my 5k time from 28.36 (week 3) to 25.10 (week 5) my cycling of 20km has been cut down to 38 minutes! Next week I will start putting a short run and then a cycle together. (Merging c25k and British heart foundation duathalon training programme!) my running has improved no end! I train alone early in the morning with the dog on runs and a once a week evening cycle. Doing the park run has massively built my confidence and speed! Even if you walk the whole thing I recommend doing it.