A couple of months ago, Runner’s World magazine published an article entitled, “Less is More.” The essence of the article was about a guy who followed the basic Hanson’s marathon schedule and achieved success with it. I read the article, which we really had nothing to do with, and was left feeling a little frustrated. The dozens of emails that we received afterwards, furthered my frustration. Not with the readers of the article, but with the author of that article. I feel like it is misleading. From the title alone, it suggests that you can run a marathon on less training, particularly the long run. For the purpose of simplicity, let’s begin with the long run and where the 16 mile long run came to be.

I want to begin this discussion by pointing out that the 16 mile length is not a magic bullet, not is the 20 mile distance. Somewhere along the last 40-50 years, the 20 miler was deemed a necessity for marathon success. It probably comes from the idea that most people tend to “bonk” at 20 miles. That still leads to the question, “Why do we use 16 mile long runs in our training programs?” To that question, there are several answers. Let’s examine them.

The Time Factor: By this I am talking about time on your feet. Research has shown that there are two critical time thresholds for enhancing aerobic fitness at the cellular level. The first is 30 minutes and the second is 90 minutes. Since we are talking about long runs, 90 minutes seems to be a good introductory time frame. Research also shows that after 3 hours of running, you have crossed the point of diminishing returns. What I mean by that, is the structural damage to your muscles, along with fuel depletion, that you are going to have to take several days to recover from a singular run. Take a look at this chart:

Per Mile 16 miles 20 miles 7:00 min/mile 1 hr 52 mins 2 hrs 20 mins 8:00 min/mile 2 hrs 8 mins 2 hrs 40 mins 9:00 min/mile 2 hrs 24 mins 3 hrs 00 mins 10:00 min/mile 2 hrs 40 mins 3 hrs 20 mins 11:00 min/mile 2 hrs 56 mins 3 hrs 40 mins 12:00 min/mile 3 hrs 12 mins 4 hrs 00 mins

Table 1: Total time a 16 and 20 mile long run would take for common long run paces.

The point here is that there has to be a delicate balance between optimal aerobic development and avoiding significant structural damage. Too little of a long run and you don’t stimulate the proper adaptations. Too long of a run and you have to take too much time to recover from one singular training run. This takes away from other valuable training before and after the long run.

The Percentage Factor: When you look through popular coaching books, you will see that a long run will constitute 25-30% of one’s weekly long run. However, when they get to the marathon sections of their books, they seem to abandon those basic training principles. In some programs you will see long runs constitute 50%, or more, of the weekly mileage total.

There are a couple problems I see with this. The first is that it means a person is probably only running 3-4 days a week, counting the long run. This means that the mileage over the other days is very small- probably 3-5 miles over the other days. That is ok if a person wants to simply complete the act of finishing a marathon, but to me, it seems like the runner would want the best experience possible for such a grueling event.

Some people may argue that a longer long run will better prepare them. I will disagree. That completely goes against another basic training principle, which is balance in training. When you are focusing on one run a week, that’s not training. That is preparing every week for a single run that breaks you down so much that you need 3-5 days to recover from. There’s no continual adaptation occurring.

25% 33% 50 miles/week 12-13 miles 16-17 miles 60 miles/week 15 miles 19-20 miles 70 miles/week 17-18 miles 23 miles 80 miles/week 20 miles NA 90 miles/week 22-23 miles NA

Table 2: Long run distance for marathon weekly mileage.

As you can see from the chart that when you look at basic long run principles, for the average person training for a marathon, a 20 mile long run falls outside from the basic principles. Now remember the time factor as well. You may be running 60 miles a week, but a 20 miler may take you 3:20, while a 16 miler may take you 2:40 minutes. The 16 miler is a much better fit because it fits into the time frame sweet zone, as well as meets the percentage criteria.

Cumulative fatigue: The idea of cumulative fatigue centers around the long run. When you look at a lot of other training programs, there is also a primary focus on the long run. However, the idea of cumulative fatigue means that the runner is going into the long run slightly fatigued from the training during the previous days. It also means that training will resume as normal the days following the long run. There isn’t a single day that is overly difficult for the runner, but every day is tough enough that there isn’t a full recovery between all runs of major importance. In other words, the long run is literally in the middle of the training cycle, not the end of the training cycle (weekly).

Putting it all together: So, with the information presented, it becomes clear that it’s not the 16 miles that is the magic number and it’s not 20 miles. It’s what works based on the numbers. A long run needs to be in the sweet zone of time on your feet, but also within a reasonable percentage of training volume for the week. The reason we use the 16 mile run in the clinics and free schedules is that it fits with the mileage that our runners are hitting and the paces that they are running. The long run provides the training stimulus needed for marathon training, but also provides enough freedom to engage in runs that are just as important for marathon training during the rest of the week.

I know that the next question will be, “Well how fast do I run my long runs?” That is a topic for another blog and I will try to address it.