A lot of our training plans, especially the beginner marathon ones will include some run walk intervals as part of the longer runs. It isn't something that works for everyone, but if you are going to be out on your feet for a long time then using this run / walk method can really help.
It's really important that you don't see walking as cheating. The fact we have had runners go quicker than 3hrs and 30 minutes for a marathon with this method shows that you don't need to run the whole way to go fast. London Marathon have even put on a run / walk pacer for this years race.
The reasons we love a run / walk are;
to better manage your effort level
to reduce impact forces going through the legs
to allow you to be on your feet for longer
You can still go fast (as we mentioned above)
With the regular walk breaks, it allows for your to have a chance to just recover every few minutes. If you wear a heart rate monitor and monitor your heart rate, you will see your heart rate drop when you walk. This will allow you to keep the long run as an easy effort run, rather than it becoming too hard.
By walking, we change the gait pattern up. When you run, you are putting a lot of force through your legs. By changing up the way this loading occurs with the walk breaks, it means you use the muscles differently and that reduces the impact forces. This also allows us to extend that long run a bit, to give you more time on your feet as part of training.
The battle with training is finding that line between training and recovery. We need to train hard but if you aren't recovering then you won't get fitter. Using regular walk breaks allows us to recover quicker from these long runs, which means we can keep trining during the week at a good level.
There are many ways of going about a run / walk strategy. The key to making this work is to make the walk breaks regular and from the beginning of your run. If you wait until you need to walk to walk, then you are already so tired that the walk breaks are not going to be of benefit. See the walk breaks as a way of slowing down how fatigued you get, not to give you more energy.
Starting off with 4 minutes running and 1 minute walking is a nice way of getting into this. Over time extend that to 9 mintues running and 1 minute walking. You may even prefer 19 minutes running, 1 minute walking. You want to keep the walk breaks short otherwise you'll get too comfortable walking! Practice these things in training, discuss it with your coach to find what works for you.
When you get into a race, if you have done all your long runs as a run / walk then I suggest doing that. What we want is for you to finish the race strongly. To give yourself the best chance of this, start off with the run / walk strategy. If after 20 - 22 miles, you are feeling good, there's nothing wrong with running the rest of the race. I can promise you that finishing strong is a lot easier than going off hard and then suffering later on, the marathon is a game of patience.