Merry Christmas all .. In a nutshell , ill be training for London this year . Currently I run a hilly five mile xcountry course on Saturdays with my club . Sunday i run the same hilly area as a LSR around 9/10 miles . I'm going to follow an advanced program by Hal higdon . Which will have me running Saturdays at pace , up to ten miles , and Sundays up to 20 ,LSR.. I was thinking of doing my Saturdays on the road . But keep my Sundays in the hills . Do you think this is a plausible idea? It's quite testing at 10 miles on these hills . At present , 20 feels like it may be to much .. I love the hills and have noticed an enormous change in my fitness levels . could these hills cause me over training and exhaustion ? I do a track session and a tempo session and a days rest . Any tips on this would be appreciated .