I did the Tough Mudder and trained for it back in 2010 when I was 180 lbs. I'm training for it now but after 4+ years of lifting I'm 197 lbs and seem to have a hard time beating a 5k in less than 26 minutes. What I'm saying is now that I'm 15+ lbs heavier I'm concerned that I'm going to have a harder time finishing the Tough Mudder this year. Was considering running with a backpack filled with some weights. Any recommendations for running 10+ miles? Training tips?