The last six miles of any marathon demonstrate why this is a problem. I keep a 60 mpw but would like to step it up to 70-80 to try and smoke the surf city marathon this february (I ran a 3:32 last year there) 1 mile roughwater swim today- feels good to give the legs a little rest. +1 Great time at Surf City - I also ran it last year. I was on pace through mile 22 for a 3:48 finish, but bonked hard the last four miles and came crawling in at 4:09. My base was 35-40 mpw. I've now kicked up my mileage to 50-55 per week. I'm hoping this will help me to come in ~3:45 in Long Beach in October.