One of the more difficult aspects of training for marathons is balancing the use of long runs and mileage. The title of this post has "the long run" showing up twice because of the two very distinct ways long runs affect marathon performance.
Let's look at the two types of long runs. A descriptive name for the first type of long run is the "on your feet" long run. Pace really does not matter with this long run just the total number of foot falls. If we look a world class marathoner number of foot falls we might see something like this: 180 footfalls per minute for 130 minutes for a total of 23,400 footfalls. A four hour marathoner would look something like 150 footfalls per minute for 240 minutes for a total of 36,000 footfalls, over 50% more wear and tear on the legs. As a matter of degree the four hour marathoner has a much bigger problem with mechanical (eccentric) induced fatigue. Efficient runners like Frank Shorter or Lasse Viren (light weight, excellent mechanics) may never need very high footfall runs to run a great marathon. Most runners who run 2:35 and slower marathons need training to counteract the effects of foot strikes but even faster runners depending on the efficiency of their neuromuscular coordination or if they will be racing on a downhill course such as The Boston Marathon will need training to counter mechanical induced fatigue.
The training effects of these "on your feet" type of runs last at least 6 weeks so when planning your schedule the last one only needs to be done between 4 and 6 weeks out from your planned race. The training session itself need not consist of just running, walking an hour, running two, then walking one more hour will get you to 30,000 or so foot strikes. You could mix it up by running for 20 minutes then walking for 5 or running 10 and walking 3, just keep in mind the objective to be on your feet for a long time. One last point running these on hilly courses if available enhance the effectiveness of the run.
The second type of long run focuses on the ability to maintain a steady state, the ability to deal with rising core temperatures, low fuel, fluid imbalance, and getting use to the sensations that come from these imbalances. In general this run is at least 90 minutes long and run at 90% or faster than marathon pace. Runs where you run the first 60 minutes at 90% race marathon race
then add 30 to 60 minutes of running at 95-103% race pace gives excellent results. The first 60 minutes gets the body up to temperature, uses a fair amount of fuel, and depletes fluids. The next 30-60 teaches your mind to accept these imbalances while running at race pace without shutting everything down. Three or four of these type of long runs (spaced 2-3 weeks apart) are all you need to reap most of the benefits. The hardest long run of this type should come 5 weeks out from the goal race, you can add an easier maintenance type run between 2-3 weeks out during the taper phase of your training but it should be well within your capacity.
Mileage is the enhancer when it comes to long runs. Whether you are running either type of long run, the miles you run the the week before, the day before, or the day after can enhance the effect you are trying to achieve in training. You don't want to be exhausted going into to these runs but not being 100% fresh will make race day when you are fresh a much better experience. The most critical time for good consistent heavy mileage is from week 9 to week 4 out from your race.
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