Canoe trip and longer runs

I had alot going on the last few weeks.  Going back to the end of week 3 - I did my MP 'tempo' - really hard to keep a 7:30 pace - but managed to do it down to Alewife and back up.  The next day I did my 13 miler - which felt really hard - down to Cambridge and back up through Belmont.  I then interrupted training to do a 4 day canoe trip up the Allagash.  It was a lot of work - but mostly arms/shoulders/back.  We did 6-8 hours of paddling each day - and covered 68 miles.  Good news: feet got a nice break from running.  

Running has been difficult since I got back.  I did 3,6,3 last wedn, thru, fri - and then the 4 mile MP Sunday - which felt real hard again.  I dreaded Monday's 14 miler - and suffered a lot.  I walked a ton the last half - and basically run/walked the last mile.  Just really hard.  I don't remember having this much trouble with the summer long runs during my previous marathon experiences.  Hopefully I come around.