I have ran 2 marathons now, all my training (upto 22 miles) shows that i should complete the marathon in just under 4 hours.
Both the marathons i have ran (London - 4:18 then Buffalo - 4:09) my pace has also been close to the 4 hour mark, when i get to 18/22 miles i seem to burn out & really slow down.

What can i do in training to improve my stamina to keep a good pace for the whole 26 miles?

Any tips would be much appreciated.

Thanks
Ross

Hitting the wall in marathons is very common until you get your training tuned just right. Generally it's a matter of not developing your aerobic system properly. Frequently this happens because you are running your long runs at or near your marathon pace. If you do this, you will be teaching yourself to deal with pain but not building the capability to use fat as a fuel source efficiently. Most of your long runs should be 10-20% slower than your marathon pace, especially while you are early in your training cycle. You should only get close to marathon pace in long runs for perhaps the last several miles of one or two long runs. If not, you'll always be at the high end of your aerobic zone, possibly anaerobic towards the end, and hence you will always be using mostly carbohydrate for fuel and not learning how to tap into your fat sources.

Thanks for the info Formationflier.
If i train 10 - 20% slower than my marathon pace then when marathon day comes would my body not automatically limit my pace to that of the training runs?
Thanks
Ross

Seems natural and intuitive, right? Believe it or not, it doesn't take much time at marathon pace to be able to deal with it. By the way, I was stuck at 4+ hr marathons for a while as well until I revamped my training. Within 2 years, I was sub-3:15, and another year to sub-3:10. I rarely run a training run faster than about 8:30/mile pace, usually slower than 9/mile pace. If you can run some hilly courses, slow down a lot on the ups and speed up a lot on the downs because that will keep you well into the aerobic zone but the downhill parts will give you practice at faster turnover. Of course it's much easier to do this with a heart rate monitor and I describe it in the running articles section on this site, but you can probably do it without one.

The long runs have to be really slow, once a week your have to run a little faster than quick walking (60% of you are max heart rate).If you are 40 you have to run with heart reat 120-130 NOT FASTER!!!
On the other hand search a little your nutrition. Many meals of spaggeti, rice, potatoes, bread are usefull the last weeks before race