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September 8th, 2021

6 Reasons Why You Should Consider a Shorter Long Run

by Brendan Martin, DPT, PT, FAFS

Controversial opinion alert: you don’t need a 20-miler in your marathon training plan.

Now that we put that out into the universe, let’s unpack it. There’s actually a number of good arguments on both sides of the 20-mile divide, and hitting that milestone (sorry) can be a huge mental boost for a lot of runners during marathon training. But is this right for everyone? Not necessarily. There are a number of variables to consider, including but not limited to:

  • Goal race time/pace: in other words, how much time do you expect to spend on your feet, on race day? 
  • Overall weekly training mileage
  • Amount of experience

Given these variables, here are six reasons you might consider ditching that 20-mile run in favor of something shorter:

  1. Many runners attempting a 20-mile training run may end up running for well over 3, 4, 5 or more hours during that run. That extended time spent on feet makes a 20 miler a far more taxing experience for the 5+ hour marathoner when compared with a 20 miler for a 2:40 marathoner. Consider instead something like a 16-miler, which is still a long time out on the roads or trails, but not so long that it leaves your body unable to recover for the next week’s training.
  2. The classic rule of thumb for long runs is that your long run should not exceed 20-25% of your weekly mileage. If you are running 30 miles per week – a very strong amount – then a 20-mile long run will come out to a whopping 66% of your weekly mileage!
  3. Relatedly, consistent weekly mileage has been proven to be more beneficial for distance running success than long runs alone.  If your long run is so rigorous that you need days and days to recover, your weekly mileage will suffer. The number one rut I see my patients fall into (and end up in PT) is being so beat up from their weekend 20-mile long runs that they do not run again until the following Wednesday or Thursday. Those runs then tend to be super short and easy until another whopper of a weekend long run. This is a vicious cycle and almost always ends in an injury. Further, overall weekly mileage is more likely to boost your chances of success than big long runs alone. 
  4. Consider your experience. Runners with years and years of marathon experience will be at less of a risk for sustaining an injury from super long training sessions because their bodies have become more habituated to the repetitive loading forces of running. Conversely, beginner marathoners are more susceptible to injuries on very long, repetitive runs. Spreading the loading forces out over two days can give your muscles, tendons, joints, & bones a breather to recover before more running. Which leads me to…
  5. Stack Days; You may be able to spend more time on your feet in a given 24 hour period by running a medium-long run on Saturday, followed by a slightly longer run on Sunday. For example, 10-12 miles on Saturday and then 14-16 miles on Sunday allows you to cover the entire marathon distance in the course of one 24-28 hour period! Certainly a strong marathon training stimulus, especially for those expecting to spend quite a few hours out on the roads.
  6. Running form efficiency & economy; Generally speaking, our form is at its best early on in a run and begins to deteriorate as our muscles and energy systems begin to fatigue.  The longer you go, the greater your bad habits will tend to be. By shortening the long run from 20 down to more like 16 miles or so, you cut out 4 miles (approximately 40 minutes or more!) of “damage time” where you may be landing a little sloppier and loading your system less economically. Once your muscles are too tired to shoulder the load of absorbing ground reaction forces, those forces find their way to other places, such as your knees, hips, low back, etc.

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