For the seasoned marathoner, pushing for that PR or Boston Qualifier, speed work is going to be your best bet to get you to that next level.  What we do for our bodies, physiologically, during our weekend long "slow" runs is increase our endurance, our ability to better sustain the ravages that long miles have on the body, and increase our fuel burning efficiency [see "THE LONG RUN" for more].  What speed work does for us is increase our sustainable speed and stamina [ability to run fast, more comfortably, for longer periods of time].  Together, long "slow" runs and speed work prepare the body to run longer and faster with more efficient utilization of our limited energy supplies over the course of 26.2 miles.

Speed work is very tough on the body, so we incorporate it into our training week very carefully... careful not to do too much, or we risk injury.  The rules are: 1.) the faster we go, the shorter the distance, and 2) always allow two days minimum before the next hard run for adequate recovery.  There is a lot of literature out there on how to do speed work, what specific speed workouts are best for what type of race distance, etc.  I urge everyone to absorb as much of this literature as you can.  Start with the literature that came with your membership in this program and other available programs, then check out articles on running web sites, magazines and newsletters... LEARN!, LEARN!, LEARN!  However, for marathoning we generally want to work on increasing our stamina through sustained pace-type runs, and longer fast repeats, rather than shorter sprints.

The following types of speed work runs are examples of what can be incorporated into your midweek runs.  Remember to ALWAYS include a minimum 1 mile warm-up and 1 mile cool-down, at slower than long "slow" run pace, into EVERY run.

PACE RUNS: These are the easiest to understand and incorporate into midweek runs.  The concept is simple, determine your goal race pace [Boston qualifier?] and run this pace for the entire run [excluding warm-up/cool-down].  If you do only one speed work run per week, this is the one you want, it will get you comfortable with your goal race pacing.  Check your goal pace against "effort" or heart rate... these should be run at ~85% HRmax.

TEMPO RUNS: These are a little more challenging, consisting of a build-up, then step-down, of pace.  After warm-up, run 1-2 miles at "pace", then 2-4 miles in the middle of the run at a pace that's slower than 10k race pace by 10-15 seconds, then finish with another 1-2 miles at "pace".  Example for an 8mile run: 1 warm-up, 1.5 miles "pace", 3 miles 10k pace less 15 seconds, 1.5 miles "pace", 1 mile cool-down.  For those running more than one speed work run per week, this is a good one to add.  These runs will increase running economy and VO2max threshold [the point at which your body starts to burn fuel anaerobically... a less efficient use of fuel].  These runs enhance capacity to run sustained distances at speed, and the speed at which you can run a fixed distance.  Check your fast pace against "effort" or heart rate... these should be run at 90-95% HRmax.

REPEATS [often referred to as intervals]: As the name implies, this type of run consists of "repeating" a specified distance, with some measure of time or distance ["interval"] between repeats.  These are the toughest runs on the body and mind... sustaining a faster than 10k race pace over a fixed, but shorter distance, and doing several in a row.  There are all sorts of suggested repeat distances [400m, 600m, 800m, mile], number of repeats [4, 5, ..., 10], interval distance/time, and target paces... too exhausting to try and pick "one" that's best.  Generally, however, marathoners will gravitate towards the longer repeat distances [800m, 1 mile] and target a fast enough pace that gets their "effort" or heart rate into the 95-100% HRmax range.  These runs should be incorporated sparingly by "advanced" marathoners ONLY... risk of injury is greatest with this type of speed work!  These runs will increase speed, strength and "anaerobic capacity"... increasing leg speed, leg strength, running efficiency & lactic acid tolerance.