Maximum of 20 mile runs during marathon training?

I have noticed that all of the beginner marathon training plans I have looked at have a maximum training run of 20 miles. Why is this?

Most common reason given is that if you ran marathon distance in training you are increasing your risk of injury. 20 miles is the compromise of going far enough to simulate marathon distance (and the associated physiological changes) without increasing the risk of injury.

Also, you may want to view it as a timed rather than a distance run.  If your running it at a minute or more slower than marathon pace, then your getting close to the amount of time the marathon will take  Its training your body to continue running for the duration of the marathon rather than the distance.

longer and you are risking more injury and longer recovery time.......

when you have been running regulary for years you can probably go longer without damage and you should be able to recognise the signs of injuries forming and step back rather than blindly following a plan

Agree with the others. I was told that if you can do 20 - the adrenaline gets you through on race day.

Even Paula and liz in their marathon training never went above 20/22 miles.

Most beginner plans only allow a maximum of 16 weeks for training, including the taper, so only say 13 weeks to build mileage. To build safely to longer than 20 miles from a low-mileage base takes longer than that. So if you want to go further than 20 miles safely in training, you need to start further out from your marathon, give yourself longer to build up. Also, you need to run your long runs sufficiently SLOWLY, and with good enough during-run fueling (e.g. malt loaf, fig rolls, whatever) that you can recover within a day or two.

To give an example of a totally different approach: I ran my first marathon (M'cr) end of April this year. I was back to HM by October 2011 (having been building back from end of May after four months off due to injury) and running maybe 30 miles a week. I then deliberately trained for and ran a 50K in mid-February, so I spent the best part of four months upping my mileage (from a starting point of HM) while dropping out the speedwork. By mid-December I was reaching 20 miles long runs and 50 miles a week. Because I wasn't trying to do fast running (except the occasional parkrun), when I got a hamstring tendon niggle I was able to cope by just slowing down further, not stopping running (I did stop for a week when I had a bad cold). Training included a couple of runs longer than marathon distance, each with a 10-12 mile run the next day (yes, those were tiring; they're called back-to-backs and are common in ultra running training). After the 50K I actually REDUCED my mileage but added some speedwork back in before the marathon.

I found that the psychological advantage of having gone over marathon distance was huge on the day of the marathon. However, I didn't try to go over distance before my first 50-miler, in August this year!

Thanks all. Debra, lol going over distance during training for a 50 miler might be a bit extreme.

As I read your posts the penny dropped. Debra is absolutely right about the fact that most beginner plans are over a 16-18 week period and therefore it makes sense that you would not want to increase your mileage beyond 20 miles in such a short period of time.

However, what I came to realise is that I had not considered speed in the equation. When I can run 20 miles in training I guess this then opens the door to working on my speed, something I have been thinking about more and more recently.

If I do not miss any training weeks my marathon training plan actually finishes at the end of January. Since the VLM is not until April 21 I guess this actually gives me some time to try and work on improving my speed during Feb and Mar. Cool!

Be careful with "working on speed" though.  Even if you've got a few 20 milers in your legs, running too many miles close to race pace still takes its toll on the body.  You might still be better off keeping your race pace efforts for shorter runs.

Put it another way and it's quite simple.  The difference between running full distance in training compared to race day is that on race day you can afford to completely knacker yourself out and leave every last effort out on the course.  You will spend the next week walking like John Wayne, getting other people to make you cups of tea, and eating crap.  In training, guess what - you've still got a marathon to train for!

PhilPub is right. Your LSRs should remain slow, except for maybe the occasional progression run when you run the later part of the run at your target marathon pace. But when you've done more LSRs, you recover faster and can do (shorter) speedwork sessions - repeats and tempo runs - during the week.

Philpub is right. I was told to just train for the first one and get used to being on my legs for that long and use the second/third/forth marathons to work on my speed work and reducing down the time.

I don't want to sound patronising but you need to learn to walk before you run - so give your body time to adjust. You've just started running seriously this year -so give yourself a break.

Makes perfect sense for beginners plans to max out at 20 miles or so. 

Its a big psychological boost - "only 6 miles to go" and you do that distance after a week of running. So come the big day - fresh legs and race day adrenaline gets you through. 

I think theres a case for runners with several marathons experience to up the mileage a bit though. I used to do the 20 miles max and I'd fade a bit towards the end. 

Last marathon I ran a couple of 22 milers and one 30 mile ultra.  All at a nice steady pace though - NOT race pace.  I PB'd the marathon. 

I've seen a lot of people recording great times for their long runs in training, 20 miles or so at marathon pace, but quite often - their actual race time is disappointing. So definitely slow it down.