i'm attempting to build sustainable speed, in an effort to lower my 5k, in the short term, but also affect my marathon time. the problem with doing track workouts is that i really don't have any idea what i'm doing. i couldn't run for college because i was too slow at the time (and probably too slow now), so i don't have the luxury of a former coach's knowledge.
i used to do 400 repeats with a slow jog rest, at least 2:00. this seemed to get me to a certain point, but i'm stuck doing them at 1:15 a piece, sometimes 1:13-1:14 if i'm having a good day. i'm thinking about changing the workout to 3 sets of 4x400 in 1:18 or 1:19, with 100 or 200 meter float recoveries. does this seem like a good idea? is this similar to stuff you do in college to build sustainable speed in relatively short races?
in addition to this, i plan on doing mile repeats in the same fashion, cutting the recovery to maybe a minute and doing them a little slower, but doing more--7 to 10 maybe. the last day will be a 20 minute tempo run with hills at the end.
just some numbers, my pr's are 16:38, 34:45, and 2:44. by next summer i'd like to crack into the 15's for 5k (even if by a second) and maybe 2:35-2:37 in the marathon, depending. i'm more concerned with the 5k in the short term--my next one is the local podunk turkey trot on thanksgiving. my next marathon is at pittsburgh, so that's a secondary concern.