Gambler wrote:
This is one of the most coherent, on-topic, informative threads I have ever read on letsrun. Well done, everyone.
Also, yes 15 is better than 10 and 5 generally, but you can probably do 11 and 5 if you split it into a double. Nitpicking sure, but like other posters mention - you drastically reduce the odds of injury.
Also, take the easy days easier and put tempos in there once a week (for you, something like 5 at 5:20-10 pace).
The odds of injury are not the big reason that doubles are better. The training stimulus IS. We all know that 5 miles is much more effective than 2 miles, and more than the 2+ times more effective that we think it should be. We all know that 10 miles is more effective than 5, right? And it is slightly better than the 2X we expect it to be.
And by better I am talking about better at BUILDING mitochondria. But the toll it takes on our muscles is greater, and somewhere around 65-75 minutes is the sweet spot for the ratio of biogenesis and wear/damage. 15-20 miles is better, but it is not so much better that the damage is outweighed by the greater biogenesis. The marginal increase in damage is greater than the marginal increase in biogenesis. That is why we do truly LONG RUNS (different lengths for different people) once per week or so.
John Kellogg has a brilliant article (15 years old) on this website about this very concept and I think it is called "The Stepwise Nature of Distance Training."
Carry the opposite of this concept to fruition and you would be doing 4-5 thirty mile runs per week. This obviously doesn't work. So we know that fifty 2-mile runs don't work and we know that four 30-mile runs don't work, so why does 10-12 miles work best?
That is a good question. The length of a training run should be NEAR that point that stimulates the growth/density of mitochondria maximally before the point that the body is torn down too much. So look at it as gaining 1.1 units of (we'll call it Mito Growth) MG for each .9 unit of (muscle damage) MD, for each minute run at a specific pace. Which (in my opinion) happens between about 55-75 minutes. (these are just numbers I pulled out of the air for illustration). At lower durations (say 2-6 miles) it is even greater advantage, say like 1.2 vs. .8 ... but the overall damage is not so great that you aren't still making ADDITIONAL marginal gains by running beyond say 40 minutes and putting in 65-75 minutes.
It is beyond this duration (as JK said 35 minutes, 70 minutes and 1:45) that additional gains are still made, but I would peg them at like .9 units of MitoGrowth vs. like 1.1 units of MuscDamage.
You see the relationship inverts. And every minute you spend running beyond about 75 is certainly helping you but the marginal COST (in muscle damage) is greater than in the first 35min and the second 35min.
You see you have reached the point of diminishing returns. therefore keep the runs to between 2-3 miles at the low end and 10-12 miles at the high end.
I know that many greats run 15 miles 2-3 times per week frequently and that Lydiard preached a 90-minute run twice a week and both of them are right to do this. This kind of volume is for the best among us and those who have run 90-120 miles a week for a while. Not for aspiring D3 runners who have run 14:58.
So that is why 5 in the AM and 10 in the PM is the ticket.
Now that I have typed a novel ... i would suggest you check out JK article. I read it 15 years ago and it made sense of my long held beliefs that I could not articulate very well myself.