how to practice the "second half" of a marathon or half marathon

This works:

Long run Saturday.  Medium-long run Sunday.  That run on Sunday will be on tired legs.

Don't forget to keep up on your nutrition and hydration. This plays a huge role in any runs 1 hr or longer. Start your sugar intake early and keep on it every 20 or 30 minutes to keep the glycogen stores tapped off.

In the 2 marathons I have done I have negative split both of them and passed 30-40 runners in the last 6 miles and I attribute a good part of that to keeping up with my nutrition.

Good luck!

My coach has me do my long runs with varying paces. For example, when I was doing my IM training, a long run of 20 miles mile go something like this....

5K warm up

5 X 5K where 1,3,5 are at 10K pace, 2 & 4 are at MP.

balance cool down.

She is famous for giving me long runs where the speed work is at the end. Another example for me might be 5 mile warm up, 5 miles at MP, 1 mile ez, 2 miles HM pace, 1 mile ez, 2 miles at 10K pace, 1 mile ez, 1 mile at 5K pace, 2 miles ez cool down.

I have had very few long runs where it was all ez pace. In fact, maybe in 2 years I might have had 3 or 4.

The second 1/2 of a marathon doesn't have to hurt. Aside from nutrition, as I mentioned before, you will also be rested and tapered. A lot of people forget about that. Your pace can easily be :30 to 1:00 faster being tapered well from your long run paces.

It's important to go into the race relaxed and ready rather than nervous and tense.

rstocks3 - 2009-01-20 12:17 PM It's important to go into the race relaxed and ready rather than nervous and tense.

And adequately trained* .......

(*Adequately trained varies per individual fitness level and past training experience.)

I just did my first marathon, so yay I get to comment on this.  Ya long runs were at around a 10 min per mile pace sometimes 11 min per mile pace depending on fitness, fatigue etc. 

For me the guiding principle was percieved effort.  I ran my entire marathon by percieve effort, basically at a conversational level z2 or whatever.  This put my first half as faster than my second half because it was much harder to run that last 4 miles than it was to run the first 13.  I was able to not walk at all. 

Basically you need to build up the endurance at a pace you can maintain so that you can maintain a pace at a given percieved effort level.  You can then inch up the pace while maintaining the same effort on the long runs.  On your other runs you work on improving speed, and ramping your system to have more power, red blood cells, fast twitch mucles, all that stuffs.  But on the long runs you need to develop that staying powa to get you to the end without burnin to a crisp and walking 6 miles. 

Anyway my 2 coppers, follow a decent plan, get in 3-4 20 mile runs and get weekly vollume up to 45-50 miles per week and you will be ok in a first marathon (at least that was my plan and it worked well for me). 

Oh and it was true about the taper knocking that much off.  I did a 21 mile run 3 weeks before the mary at a 9:15  pace and ran the marathon at an 8:40 pace, almost 30 min off what I had expected due to that taper and race effort (ya I tossed in another 15 min based on assuming I would drop off from the 9:15 pace over the last 5 miles to make up the difference in the math there).