We continue our series of advice columns ahead of the London Marathon by looking at the some of the pitfalls that club runners fall into

Breaking the 2:30 mark for the marathon is often seen as a solid benchmark for a lot of club runners. Yet far fewer achieve this than seems logical.

According to the internet time calculator that I normally use, someone who is capable of 2:30 for the marathon could typically do 32:36 for 10km off the same fitness, though obviously this varies according to the individual, dependent largely on mileage background and natural strength versus speed capacity.

Of course, fewer people run the marathon distance compared to shorter events and there is the fact you have far fewer attempts at 26 miles. However, I’ve long thought that many are under-performing at the marathon.

So why might this be? Why aren’t more breaking the two-and-a-half hour barrier?

First, so many are getting the pace wrong. Take a look at any flat marathon (London is not the best example as it has a slightly easier first half) and you would be staggered to see how many at around this level run much quicker over the first 13.1 miles than the second.

Pacing the marathon is not an easy task, especially for beginners, and even the most experiences can get it wrong occasionally. However, if you’re getting it right, you should be thinking during the first half at least that it feels easy. I can recall on the one occasion that I broke 2:30 (2:28:32 in London 2011), that I was thinking at about 16 miles, “This is a marathon – isn’t it supposed to be hard?”

Now on that occasion, it could be argued that I went off too slowly as I ran a massive negative split, so you have to be careful of this too, but by the far the biggest problem is starting too quickly.

I also wonder whether many are putting in enough miles in their training. Of course, some individuals can beat 2:30 on their debuts without increased mileage and just rely on their talent. But for most of us, if you want to run as well over the marathon as you do at shorter distances, you will need a lot more miles in the bag.

Built up gradually over five to ten years, 100 miles per week, including two or three hard sessions shouldn’t leave you feeling tired.

With this, a few long runs of around half an hour longer than you expect to take for the marathon are important too – just to get used to the distance.

Another big mistake I always see is people trying to merge their long runs and long marathon-paced tempo runs into the same session. Long MP runs are “long” in the sense of being longer most of your runs, once you add in a short warm-up and warm-down. However, they should be quite a bit shorter than the longest long run distance that you are used to. But they are not “long runs”, which should be all about time on your feet at an easy pace.

When it comes to race day, one last thing that might not receive enough attention is that of hydration and nutrition. Perhaps I am being too clinical in planning exactly how much I will consume in the way of carbs and water and when, but it strikes me that this is a precise business.

You don’t want to consume too much liquid – after all, take just half a litre more than you need and you will end up 500g heavier and two seconds per mile slower, in theory. On the other hand, some can lose a lot more than a litre per hour in sweat and, according to many – though not all agree – being more than 2% dehydrated can worsen your performance.

Even with such meticulous planning, I don’t pretend to have got the matter of hydration and carbohydrates right yet. Some have been lucky with the gung-ho approach, while for others perhaps this is their downfall.

» Paul’s blog post is the third in our series of pre-London Marathon blogs by AW writers and you can find the other posts in our blog section here

» Note: A version of this blog was first published on athleticsweekly.com on April 17, 2013