Most of you are probably aware by now, that I push speed work. I do this because the majority of high school runners and adult 5k-marathon runners that I talk to go on long, long slow runs and don't try to push their pace much. I'm always telling people to get on the track or throw some intervals and progression runs into their normal running workout. So much, that I may have you doubting the importance of the long run.
The long run. Very important. It builds muscle, grows capillaries (which take oxygen to your muscle), and strengthens tendons, bones and ligaments. All of these things help you to run economically and stronger.
BUT instead of going out and plodding along for 90 minutes to 2 hours, try running the last 30 minutes fast, or progressively getting faster every 30 mins(negative splits), or add 15x15 second sprints throughout. Do this unless you're a newbie to the long run, in which case just plod until you feel comfortable with the distance/time. Having said all of that, make sure your long run is easy! Do some long tempo runs (like 3 miles x 2) or longer intervals (like mile repeats) the day before to make sure your already slightly beat up going into your long run. You don't want the long run to come at the expense of your race specific training.
This post is for everything...the 1 mile to the marathon. Get some distance on.
I would throw in the long run once a week and a shorter, but still long run somewhere else in the week too. And what should you do the other days??? SPEED!