I have been working on trying to reconcile some different schools of thought in running. Previously, I have discussed Maffetone low-heart rate training and how it may be effective. However, what I find is that it seems to work well for some people and not very well for others. Rather than chalking this up to "everyone is different," I want to propose a hypothesis.
For a positive example of low-heart rate training, you have people like Mark Allen who have said they've benefited from the program. You also have evidence that top runners spend the majority of their training time running at easy paces. In one study, top runners ran 71% of their mileage at a low-intensity.
On the other hand, you have many people who are critical of low-heart training. You can have to look at the growing popularity of websites like Crossfit Endurance, for example. These websites attract those who have not done well with LSD training. The popularity of these sites suggests that low heart-rate training isn't working for a number of people.
You also have the personal accounts of those who have tried low-heart training but it hasn't worked for them. For example, here is a quote from the Fitness Intuition website:
"I spent years training slowly for ultramarathons. Ten-minute miles were typical, 9 minutes was fast. My goal was to finish. I occasionally wondered if upping my mileage would improve my race times. Yet the thought of piling up more miles of slogging was appalling. Here’s a funny thing. From the first day I began training faster, my enthusiasm soared, and I found it easy, even exciting, to pack on the miles."
I also have my own personal experience. During my training for my one and only marathon, I just did a bunch of slow miles. I didn't get any faster, and in fact I got a little slower. So why didn't the approach work for me either?
I think the key to all this is the new research on the optimal running speed of humans. In the study, it showed that for a group of runners, the most energy efficient pace was between 7 and 8 minutes per mile. (This study was done on a treadmill, so the optimal pace may be different if there are hills or if the running is done on a trail.) At this pace, humans have the lowest energy expenditure compared to faster or slower paces.
What I'm thinking is that this pace represents a "sweet spot" that generates the most benefits from distance running. For an elite runner who can run 5 minute miles, 7 to 8 minutes probably qualifies as low-intensity. Therefore, an elite runner can run at this low-intensity and increase aerobic fitness.
For a slow runner, running at a low-intensity means running at 10 or 12 minute miles (or slower). At these slow speeds, a runner is not in the sweet spot and therefore is laboring (expending excessive energy) to perform the running. The next question is, will training at these slower paces ever lead to a person improving and being able to run at 7 or 8 minute miles? I am starting to think the answer is no, or at the very least it is a long, slow process that may not be the right way to do it.
