The long run might be considered the cornerstone of any distance running program. The long run (and long is a relative term, right?) sometimes takes on a mystical quality. Everyone knows you are supposed to do a long run, but why? I am going to limit this blog to the long run as it relates to marathon preparation.
Okay, it makes sense that if you are going to run a long distance race that you need to run something close to that distance in training. Some training programs will have you run longer in training than you will race. I was listening to an interview with Nick Symmonds, a 800m runner, who talked about doing 8-10 mile runs. His race is less than half a mile long! However, more marathon training, few programs have you run longer than the marathon distance or even come close the 26.2 miles. In the US, we tend to stop at 20 miles. I hear that in Europe they stop at 30 kilometers (a little over 18.5 miles). Why those numbers? Well we have a tendency to like numbers that end in zero. Jeff Galloway is famous (or notorious?) for having runs of the marathon distance or longer, but what people often miss is that Jeff includes his trademark walk breaks after each mile. So that 26 mile "run" is not 26 miles of running.
Psychological and physiological benefits
Let me make the case for the long run from both a physiological and psychological perspective. First the psychological: the 20 miler may boost the confidence that the runner will be able to complete the marathon distance. The runner can experiment with clothing and fueling/hydration strategies to see what works. You are also learning to deal with the mental fatigue of running for several hours. How are you going to make it mentally for running for several hours? The long run develops those strategies. Remember that many (most?) races prohibit the use of headphones during races.
Physiologically, the long run helps to improve fat burning by increasing the number of mitochondria (remember in biology that these are the power houses of the cell). Mitochondria biogenesis (the creation of new mitochondria) occurs when exercising in a low glycogen or low carbohydrate state; during the long run you create just such a situation in the muscles. Fat can only be "burned" in the mitochondria. Along with more mitochondria, the body responds by creating more enzymes that are involved in burning the fat. (I will address fat burning in another blog).
The long run is aimed at increasing one's endurance (is that a Captain Obvious statement?). Yes you need to have endurance to run 26.2 miles. Heck you need endurance to run something even as short as the 800m!
Another possible adaptation is that as you fatigue you tire out some muscle fibers and recruit other muscle fibers to provide the necessary force. You may have heard of slow (type I) and fast (type II) muscle fibers. A long run can fatigue those slow twitch muscle fibers and then recruit some of the fast twitch muscle fibers in order to keep you going at your desired pace. The adaptation is that these fast twitch muscle fibers become a little more like type I muscle fibers. (They are not "converted" though).
Another common reason for the long run is to strengthen the connective tissue such as tendons for the workload that comes with the marathon.
How long should it be?
Now, there are differing opinions about the long run in terms of its importance and how long it should be. I have read arguments that weekly mileage might be just as important. I will not disagree with that. Jack Daniels, the running coach not the liquor, recommends that the longest run of the week not exceed 30% of total weekly mileage. Well a little arithmetic tells me that in order to run a 20 miler and stay at 30%, my weekly mileage needs to be about 70 miles. I doubt many folks are running 70 mpw. Hanson's training group is famous (infamous?) for capping the long run at 16 miles. I will admit that I am not aware of any science that says 20 miles is that much greater or better than say 18 miles and that a person running 50 mpw with a few 16 to 18 mile runs is worse off (or better off) than a person running 40 mpw with a few 20 milers. However, if you have the money, I am willing to study it!
Anecdotally, people have run successful marathons (that is they met their goals) training with the shorter long runs. Heck, if you want to start a mess post something like that to message board at letsrun.com or the forums on runnersworld.com.
Some coaches favor running for a set amount of time and not worrying so much about the distance covered. I once trained based solely on time and a bit of a guess at the pace in the days before GPS watches and MapMyRun. I remember driving courses that I had run to see how far they were. I was usually disappointed that they were "short"; GPS only made that worse. I like the time idea to some extent. Alex Hutchinson at Runnersworld.com makes a few good points about using distance or time.
Colorado Springs, my home, has miles and miles of single track trails great for running. I have coached runners who do all their long runs on such trails that often involve a good deal of climbing. For those runners, I recommend running for the amount of time it would take them to cover the prescribed distance on flat ground. So if it would take 3 hours to cover 20 miles, then run on the trails for 3 hours and ignore the distance.
A definite consideration with the long run is recovery. I am not a fan of going much beyond 20 miles because it could mean less recovery and, thus, poorer training during the week after. Remember the long run is still just one component of the training plan. I will say that folks who opt for shorter long runs (is that like "jumbo shrimp"?) make this argument about the 20 miler.
I am going to wrap this up as it has gone longer than I anticipated. In the end, you need to do a little experimenting and see what works best for you. I will say that I like the concept of 20 milers; the more aggressive the goal of the runner in the marathon, the more of them I will put in the training plan. For my folks who are interested in finishing, I will have one 20 miler. If the person is aiming to BQ, then at least three of them.
If there are questions or you disagree, please comment, and I will respond.