Why does my HS coach want me doing 2-a-days?

Yes

The more you exercise, the better you get. Is this not obvious?

yes

Because it makes you a better runner.

So I know I originally answered my own question.

But what's the point of doing a second run when your legs feel like crap and you're just struggling (not dying but uncomfortable)?

it makes you better and over time you won't struggle anymore

Load, Dynamic or Static recovery, Improve.

Repeat

Years ago (decades, actually) some fairly good research was done on frequency of work bouts--not just in The Sport, but in a lot of athletic activities. Two work bouts per day are better than one.

Interestingly, a third session was not shown to offer a statistically-significant benefit compared to just two. It was still better than just one, though.

The key, really, is to make sure that the second session doesn't mean a loss of recovery time--sleep, mostly.

Lagat has done pretty good w/ one workout per day.

Most HS athletes would be better off getting the extra sleep, and that

includes physiological factors related to running, improved mood and academics.

More running is not necessarily better because volume is only one of

several key training variables.

With the exception of 10,000m, all HS records were accomplished w only moderate mileage, roughly 1 hour running per day.

dsrunner wrote:

With the exception of 10,000m, all HS records were accomplished w only moderate mileage, roughly 1 hour running per day.

This is not true.

Run 2 x per day 3 of the days a week until you get used to it.

Slow down a little until you get used to it.

Many feel that 2 - 30 min runs a day at a slightly faster pace may be better than 1 slower 60 min run per day.

I've found this personally to be very beneficial.

The extra distance is more running.

How many miles are you running per week?