Coach was suggesting that regardless of volume, we should try to ensure that our long run makes up between 30-40% of weekly mileage. He encouraged us (for those who don't already) to start peppering our training with short, easy recovery runs to boost overall mileage without tiring us out.
One person then argued that running just for the sake of adding mileage would be considered "junk miles" and suggested that you might be better off focusing on key runs only and resting or cross-training on the other days.
Personally, I don't believe in "junk miles". Just because a run doesn't include a specific workout or pace-goal, doesn't mean it has no purpose. One thing I have finally learned over the last year or so is that when I run more overall mileage, my long runs feel a lot more manageable (which would translate to the marathon feeling more manageable).
I found a great article on this topic on Running Times: Rethinking Junk Miles by Matt Fitzgerald
"Running volume ... has a positive effect on running fitness and performance even in the absence of exhaustive key workouts. In other words, the more running you do (within the limit of what your body can handle before breaking down), the fitter you become, even if you never do any workouts that are especially taxing. The reason is that increases in running economy are very closely correlated with increases in running mileage."These "bonus" runs also allow an extra opportunity to practice. In general, you can expect that doing something more (within reason) will make you better at it.
"For both the juggler and the runner, it is time spent simply practicing the relevant action that improves communication between the brain and the muscles. It’s not a matter of testing physiological limits, but of developing a skill through repetition. Thus, the juggler who juggles an hour a day will improve faster than the juggler who juggles five minutes a day, even if the former practices in a dozen separate five-minute sessions and therefore never gets tired. And the same is true for the runner."On a less "scientific" note, I love my easy/recovery/"just because" runs because they give me the opportunity to run just for the fun of it. I may not always feel like lacing up the day after a hard workout, but I almost always end up enjoying it. There's no workout to worry about and it's refreshing to go out and just run in the middle of heavy training.
What are your thoughts on "junk miles"?