Myth of the 20-mile long run

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Tim of MK Aug 2017 4:48pm, 13 Aug 2017 2,183 posts	0 Tim of MK For years, with marathon training, a long run of 20 miles has been the aspiration for many. They fervently believe that if they are able to that far (usually at much slower than race pace), they’ll be able to handle 26.2 miles (all at race pace) on marathon day. But, whilst this 20-mile milestone might feel an essential part of marathon training, is it actually physiologically better than say 18 miles, or even 16 miles for normal runners (by whom I mean 4-hour plus competitors)? Many, many sports professionals have told me there's no science to suggest that it is. Rather, research demonstrates that 90 minutes to two hours of running seems to elicit the greatest amount of mitochondrial growth. Seemingly, research has yet to show that running longer than two hours provides any greater aerobic development. So, even if there isn’t any real physiological benefit to running more than 2 hours, why not run 20 miles anyway to give confidence? Well, sports professionals have told me there are two reasons. Firstly, the longer someone runs, the more tired they become. As a result, their form will begin to break down after 2 hours plus. Major muscles become weak and liable to overuse injuries. Secondly, recovery time after very long runs is way longer than after a moderate long run. This means you not as many marathon-specific workouts can be completed through the week. Given the above, why do so many people still hold to the 'Holy Grail' of the 20-miler?
fetcheveryone Aug 2017 5:06pm, 13 Aug 2017 18,549 posts	0 fetcheveryone It's a nice round number?
Fragile Do Not Bend Aug 2017 5:22pm, 13 Aug 2017 2,153 posts	0 Fragile Do Not Bend It's not answering your question, but surely how long someone can run before their form breaks down due to tiredness is going to be hugely variable? Some people will be fine well after 2 hours and some people would be tired well before that.
Tim of MK Aug 2017 5:39pm, 13 Aug 2017 2,184 posts	0 Tim of MK Possibly is because it is a round number lol. I seem to remember French runners going to 30kms.
Joe Hawk Aug 2017 6:03pm, 13 Aug 2017 5,238 posts	0 Joe Hawk I think daniels says 2:30 hrs. Did my first off 15M, though now if training properly I would probably go to around 23M
Little Nemo Aug 2017 7:28pm, 13 Aug 2017 7,812 posts	0 Little Nemo But if it's going to take someone (like me!) over 5 hours to finish a marathon surely you need longer than 2 hours on your feet in training?
Wriggling Snake Aug 2017 7:30pm, 13 Aug 2017 15,890 posts	0 Wriggling Snake Time. Mitochondria help you convert oxygen. With the marzthon that is not sanywhere near so important if you are a 3 or 4 or 5 hour mars runner. In effect it is a different event again for people eho are slower an ultra almost. People should think of time not distance.
Carpathius Aug 2017 8:10pm, 13 Aug 2017 12,306 posts	0 Carpathius As a 5 - 6-hour marathoner, I wouldn't want my longest training runs to be less than 3-4 hours regardless of distance. Thing is, if you've planned a route, most people seem to do that by distance rather than time (which, in my experience, could vary). Also race organisers helpfully put on 20 mile races in the run up to marathon seasons
Tim of MK Aug 2017 10:27pm, 13 Aug 2017 2,185 posts	0 Tim of MK Personally, I'll likely peak at about 17.5 miles.
Canute Aug 2017 10:38pm, 13 Aug 2017 1,808 posts	0 Canute In the marathon the ability of the leg muscles to withstand damage is almost as important as aerobic capacity. One way to build up the required muscle resilience is a series of long runs of gradually increasing distance. I suspect that a 20 mile session that follows a gradual build-up is very beneficial; while a 20 miler without a good build-up might do more harm than good.