Tipping Point of Increased Mileage

So does this mean that if you do 50 miles per week that your fitness gains by 80-100%?

Once I moved up and achieved a solid base of 50+ miles per week I started to see a general improvement in my 10k times from average 41mins to 39 over a 6 month period.

As someone who spent a lot of years down in the 30mpw range due to work and family stuff, there is a big difference in fitness between 30 mpw and 50 mpw

My personal experience is that I need to be at 50 MPW to get get in good shape, while 75-80 MPW (average) is about the 'tipping point' for me where I risk injury more than improvement. Of course this is extremely individual. I know people who run well off 35-40 MPW and another guy who cranks out 100-mile weeks like they are nothing.

My freshman year of high school, I probably did 30 mpw in season, following a summer of maybe 15 mpw. I got down to low 19's (5k) in that cross country season. In track, I did maybe 35 mpw and got down to 10:50 for the 3200. The following summer, I did about 40 mpw in running, but also biked a lot and played ultimate frisbee 3 times a week, for about 2 hours each time. My sophomore year of cross country I got down to 17:20.

I think you will see a significant drop in times from 30 to 50, and probably even see an increase in fitness from 30 to 40. However, I increased my overall activity level along with my mileage, so I cannot say for sure what how much of it was due to running and how much was due to other factors.

I'm not great with the "science behind running" but I can tell you what worked for me through my own personal experience. So here goes:

I don't think there is a magical tipping point of mileage that is more effective than another. I ran at most 20-30 miles in high school. After I graduated I learned better and started running more mileage, I think I progressed something like this:

College FR: Topped out at about 70 MPW, mostly 40-50 MPWs

College SO: Topped out around 80 MPW once, again mostly 40-50s

College JR: Topped out at 102 MPW once and three weeks at 80+

College SR: Topped out with three weeks at 97, 103, 100, lots of 80s

I saw my biggest improvements my Junior and SR years. But I don't think that there was a magical tipping point where all of a sudden I ran over 80 MPW and I was magically improving.

... I personally believe it's the acclamation of MANY weeks, months, and years of running good mileage before you start to see real big gains. Running one big 60 MPW and then going back down to 30's is not going to help you as much as consistently running 50's, I believe.

My best advice, don't be in a rush to build mileage! It takes time if you want to build your mileage over many seasons and remain injury free. You can probably go out this week and bust out an 80 MPW if you wanted, however it would probably lead to injury. If you're at 25 MPW right now, I would recommend progressing something like this: 25, 30, 33, 40, 40, 45, 50, 55, 50, 60, 60, 65, etc...

There are probably people here that can provide you better more sound training advice, but I'm just sharing what I went through when I started to really build mileage four years ago. I would say that I've seen SIGNIFICANT improvements since doing so. Cheers!