Fast without speed work

Not to overgeneralize here (but I'm going to anyway LOL), many successful running programs use most of their mileage as slow/comfortable/easy, and then throw in some "speed" work in various forms.  Those forms depend on the plan and your target race distance.

For younger athletes you might see a reverse, as they don't do a ton of miles.  Again an oversimplification.

I personally dropped my open 5K from 24 flat to sub-22 running about 85-90% easy miles.  That's not podium by any stretch but it was only averaging like 15 miles/week.

Besides choosing your parents well, it depends on what you mean by "fast".   It's not the same as "faster".  We can all get "faster"......running more is one way.  You say you want to get "very fast"......in fact, you said, "So can someone explain the process of getting very fast without any type of interval training?"  There is no process for that.  You must do intervals to get "very fast".  So does your friend if he ever wants to be.

"Just run more" (tm)

first of all, no where di you friend say he was only running slow.  he may very well be doing plenty of fartlek intervals, which are undefined intervals.  or hill work.  and threshold runs etc.

second, I think the majority of people don't run enough to do hard intervals.  I know LB will chime in about junior, and to that I would say the majority of people on here aren't doing the swimming and cycling to compensate as he is.

You have to build the aerobic base and durability to do good speedwork.  When I first started I did plenty of running fast, and it got me hurt.  Now I just finished a run block peaking with a 60 mile week, and not a touch of injury in the last 3 months.  We will see what happens as workouts become race specific, but so far it seems like this has been the most productive "offseason" i've had yet. 

Dude - you know damn well that swimming and biking have no benefits to running.  Have you not been paying attention? 

Impressive stuff, how are you avoiding being constantly injured?!

also interesting that your race reports don't reflect you running a 19min 5k..

I watch a number of kids who are sub 15:00 5Ker's on the track.  None of them runs over 35 mpw or so, but it's quite a bit of speed and stress in those miles.....easy running is the smallest percentage.  Yes, I realize they are not elite 5K'ers, but I wonder how much of the thousands and thousands of yards of  swimming they do contribute to those physiological cardio adaptations you alluded to, if any.....or what moving to a more run focused training will yield for them.  I also don't think it's a coincidence that many of the kids who finish near the top of our State XC meet have swim backgrounds.

I think what you wrote is largely true........I'm always curious about what the benefits/hinderence of cross training will be on these kids I've been around as they continue with their careers.  Even the college coaches, as we talked to them during the recruiting process, were split.  Some wanted the fast kids who were running the biggest miles......some wanted nothing to do with those kids and wanted the kids who had built quite a bit of speed on relatively few miles. Some wanted them BECAUSE they cross trained, some wouldn't touch those who did.  It made no difference how strong or weak the program at the college was......the opinions were all over the place and VERY deeply rooted and strong.

I think my thoughts were kind of  touched on by a couple of people, especially by LB but fast really is a relative term.

Ultimately, I think HE answered your question: "How the heck do you get fast if you're not doing speed work intervals?" and it was "Man I ain't ever done an interval before. I just go out and run whatever pace feels good [for a year][yeeehawwwww]." So, that's how he got fast.

BUT that is by your definition of fast, as in fast to you. 

He's very likely not reaching his potential in terms of being his fastest, because no, you wont be your very fastest without a mix, including quality workouts or "speedwork". 

In regard to everyone's advice to run more. Yeah, to a certain threshold(and one most people don't exceed before diminishing gains) you WILL get faster by running more. And if you really like running, and have the time to do it, I think it's an excellent way to get you most of the way there. But if you truly want to be your fastest, there are many adaptations you need to make with different types of training stimulus. And then, when speaking specific to triathlon, the overall training load needs to be considered and leveraged. 

This is a total side bar but you always reference swimming when you talk about this. What other sports are the lower mile kids using to build their fitness? I would assume the key is simply that the activity contribute to the physiological adaptation and that it be low impact so that you can do more of it. But is there anything else about swimming in particular?