I saw this the other day from a post on FB:
This one really caught my attention because it's written by a well-known and well-respected coach, Joe Friel. However, the reason why it caught my attention is because I believe he's making some very inaccurate statements about the Specificity Principle. I bring it up because it happens to be one the most popular myths in the sport of triathlon, imho. He made the following statements:
"So how about this one… If your goal is to run a 7-minute pace you need to do a lot of 7-minute-paced running. Not 8 minutes and not 6 minutes. There is this thing called “economy” which relates to the principle of specificity. If you spend a lot of time running 6- or 8-minute pace you will not be as economical at 7 minutes as you could have otherwise been. Economy has to do with how much energy you use (or waste) at a given pace."
Ok. I'm going to be my typical outspoken self and call bullshit. I've read a ton of studies and talked to a ton of very educated people on this topic and none of them have indicated the above to be a true statement.
First off, the factors that truly influence running economy are still not well understood to this very day. However, we do know certain things. Here's a couple of quotes from some studies:
"Cardiovascular, metabolic and neuromuscular adaptations are the main physiological correlates of improved movement economy."
"A number of physiological and biomechanical factors appear to influence running economy in highly trained or elite runners. These include metabolic adaptations within the muscle such as increased mitochondria and oxidative enzymes, the ability of the muscles to store and release elastic energy by increasing the stiffness of the muscles, and more efficient mechanics leading to less energy wasted on braking forces and excessive vertical oscillation."
The point being: What we do know is that running economy tends to improve when we introduce the Progressive Overload Principle into our training. Why? Because progressive overload is what induces these adaptations.
I don't know why this myth persists in running yet not so much in cycling. My suspicion is that since the impact forces of running are much greater than cycling, the relative intensity when running must be adjusted accordingly. So, people like to create an excuse or myth as to why we need to do a fair amount of running at lower (relative) intensities, as compared to cycling, in order to justify the training purpose.
No matter how you look at it, doing a lot of running at goal race pace, by itself, is not a factor in improving your running economy. It can only become a factor when the stimulus associated with training at goal race pace just so happens to be responsible for creating an overload and therefore eventually inducing an adaptation. In order for an optimal stimulus to occur you have to consider many other factors like time available to train and other athlete characteristics. Let me give you an example:
If I was to run 3.5hrs/week during 12hr training week during a race-specific prep period then training at my IM race pace (E pace) would never achieve optimal stimulus because I could easily double that time to 7hrs (and 20hrs/week overall) before that run training load would begin to create a stress level that was high enough to be considered optimal.
Remember, whether it's E pace, T pace, goal race pace, etc, these are all just paces representing a different level of training stress. Now it's important to note that as pace increases, the true physiological cost associated with that pace increases in a non-linear (exponential) fashion. Add the impact forces of running to that and you should be able to see how easy it can be to achieve an overload in a non-progressive fashion. Meaning, it's quite easy for us to run too hard too often causing muscle damage. But it's important to understand that this damage is not necessarily reflected as an injury in many many cases.
The right combination in our training tends to be a relatively individual thing. I'd say if there's any specific pace that applies to the general triathlon population which is primarily responsible for improving running economy, it will be a faster one more so than a slower one, eg, I or T pace more so than E pace. Running hills and doing strides are probably much better ways of improving your biomechanics and therefore running economy. And note that neither of those two have anything to do with your goal race pace.
One last note:
I just want to make sure that everyone has a clear understanding of what "economy" means. Joe said, "Economy has to do with how much energy you use (or waste) at a given pace."
Energy is defined in terms of oxygen consumption; the farther an athlete can run per unit of oxygen consumed -- or, stated another way, the less oxygen he/she consumes in running a given distance -- the more economical he/she is.
Also read this: