Average distance run in a Marathon

How far do you actually run in a Marathon?

1 to 20 of 27 messages
19/03/2012 at 17:33

Aiming for a Sub 3 marathon, I know I need to cover each of the 26.2 miles in an average of 6 mins 52 secs

Problem is, at Abingdon last year I ran 26.39 miles

What distance am I likely to run at London? 

cougie    pirate
19/03/2012 at 17:48
You mean your GPS recorded that distance.

Forget the GPS and use the mile markers instead - they are accurate and GPS reception can be very dodgy with the tall buildings and underpasses.

Set the watch to beep at 6.52 intervals and use that.
19/03/2012 at 17:55
If you stick to the blue line at VLM then 26.2...however thats what everyone will be doing so you may get pushed wider, so maybe 26.3..
cougie    pirate
19/03/2012 at 18:07
We could have a sweep on it ?
kittenkat    pirate
19/03/2012 at 18:17

GPS drops out in the tunnel.

19/03/2012 at 19:30
And you can't get a signal either
19/03/2012 at 22:00
No, dodging all those people walking doesn't add half a mile
19/03/2012 at 22:44
If the marathon course were a big circle and you ran consistently 3 ft outside the blue line then you would run not hundreds of yards extra but only 19 ft extra. This is similar to the "rope around the earth" puzzle.
19/03/2012 at 22:53

I had a puzzle of a spitfire once but not the "rope around the earth" one you speak of.

20/03/2012 at 08:13

Yeah - OK.  I get it, the GPS may lose its signal around London, but if I end up running 26.3 miles as suggested by Flat Footed, my mile split is now 6.50 rather than 6.52

Any advance on 26.3?

I really don't want to turn onto The Mall as the watch hits 3 hours...

20/03/2012 at 08:21
SKB - If you configure your Garmin as follows you will be able run to an exact pace. This is a post from 'Paul the Builder'

"We probably all know someone who has got to the closing stages of a race, thinking they’ve used their Garmin to pace themselves perfectly to dip under a certain time, only to find they miss out because “the course was long”, or tunnels, underpasses and the like mean their Garmin lost signal and threw the pace number out of the window.

It doesn’t have to happen that way. Even on a course with tunnels, or with inaccurate mile markers, or even on a long course(*), you can set up your Garmin in such a way as to always know how you’re doing in the race, rather than get the nasty surprise at the end. I’ve been asked to explain on threads and fmails several times, so I thought I’d stick it here for posterity.

On the screen you’re going to look at while racing, you need to have at least these two data fields displayed:
a) Pace – Lap
b) Time – Average Lap
And you also need to switch AutoLap off. And AutoPause too, if you use that normally.

You then need to hit the Lap button at each mile marker.

So within each mile, you look at “Pace – Lap” to see how you’re doing just for this mile (don’t use Pace (current) for this, it changes too frequently).

And for the race as a whole, you can see your situation by comparing “Time – Average Lap” to your goal pace.

And that’s it. This will work for races with tunnels, skyscrapers, tight turns, inaccurate mile markers – anything. As an illustration:

Say you’re trying to break 90min for a HM. So you need to run better than 6:52min/mile average for the 13.11 mile course.

Without doing what I suggest above:
If you steady pace mile one with your Garmin pace field showing 6:50m/m, but the Garmin distance at the first mile marker is 1.01m – then you’ll actually pass the mile marker in 6:54 (but the Garmin will have beeped at 6:50 with AutoLap).
If every mile goes by like this, going by Gamin pace alone you’ll think you’ve cracked the 90min, but you’ll actually come home in around 90:50. The GPS distance will record 13.24m, and you might think the course was long (although it almost certainly wasn’t).
That would be pretty frustrating, since you might think you’d paced it perfectly. It’s even more frustrating when the margin is closer, if the Garmin “over-read” on distance is less than the 1% above.

If the same runner sets up the Garmin as above:
Pass mile one, hit lap manually – they know that the first mile was 6:54, not 6:50. The field “Time – Average Lap” says 6:54m/m. They’re slower than 6:52 target pace and are aware of it. Until they speed up and this field reads better than 6:52, they’re still behind the pace.

If you miss a mile marker, this method is not screwed up either – you just need to make a lap somewhere, even if it’s not accurate. As long as you have pressed lap X times when you pass the X mile marker, the field “Time – Average Lap” will be your average pace in the race to this point (it’s basically doing the same calculation you would do if you took total time and divided it by total race distance at that point).

Forget about Virtual Partner; since the GPS measure of distance isn’t (sufficiently) reliable you can see why that isn’t a reliable method.

(*) Officially measured courses are not long, even if your Garmin says it is. GPS cannot be relied upon to be accurate to better than 1-2% typically, so you can expect your marathon to measure around 26.5m by your Garmin."
Edited: 20/03/2012 at 08:22
20/03/2012 at 08:41

My Garmin measured less than 26.1 at VLM last year

I completely agree with the post above - just use the manual lap each time you go through a mile marker, and keep an eye on your average pace.  If you miss one, just hit the lap anywhere and so that overall you still get 26 laps marked.  I think last year I missed mile 13 because I was thinking about the half way point - so hit it when I went over the half way mat and then back to each mile marker from 14 onwards.  It meant I always knew where I was in relation to my target, and ended up beating it by 18 seconds (sprinting * the last 385 yards).

Also, the mile marker balloons at VLM are not always accurate, but they have a mark on the road which is (I think anyway!). At the sub 3 end of the field there shouldn't be a problem seeing that beneath your feet.  Some of the marks are a little way off from the balloons, as they can't always erect the balloons at exactly the right spot.  Again last year two of my "miles" at around the 5-6 mile point were a minute different in time, even though I knew I was running an even pace...I just put it down to one being a little short and one being long (in terms of where the balloons were...I didn't realise until later they had marks on the road).

Don't even look at the actual distance your Garmin is saying - it is irrelevant.

Anyway, good luck with the sub-3 goal 

* Sprinting at the end of a marathon is of course a relative term

20/03/2012 at 08:44

Thanks for posting this Badbark.  I've copied it into another thread where there's been lots of talk about garmin distances and pacing recently. 

20/03/2012 at 21:08

Badbark's advice is solid, but only if you're coordinated enough to hit the lap button each mile marker. (Or press it the right number of times after missing a marker.)

Since that wasn't me, I knocked 5 seconds off my per-mile pace and then checked that against an old school pace band/watch combo. (Yes, last race I was enough of a saddo to have a garmin on one side and a watch on the other.)

TR
20/03/2012 at 21:22
there's a big clock and a load of balloons marking every mile, you can't miss em !
21/03/2012 at 09:57

Thanks for the post Badbark & to Paul the Builder for the original

Good advice too from Freemers

Gotta get this right on race day, as well as everything else....

21/03/2012 at 10:02
Steve C.   wrote (see)
If the marathon course were a big circle and you ran consistently 3 ft outside the blue line then you would run not hundreds of yards extra but only 19 ft extra. This is similar to the "rope around the earth" puzzle.

This question came up in an episode of Beat the Teacher (circa 1988?).  It blew my tiny mind!!
21/03/2012 at 10:20
Rennur wrote (see)

Badbark's advice is solid, but only if you're coordinated enough to hit the lap button each mile marker. (Or press it the right number of times after missing a marker.)

Since that wasn't me, I knocked 5 seconds off my per-mile pace and then checked that against an old school pace band/watch combo. (Yes, last race I was enough of a saddo to have a garmin on one side and a watch on the other.)


Similar here, since I prefer not to have to press the lap button manually.  (Especially since, pre-Garmin I would use a bog-standard HRM/stopwatch and on more than one occasion forget, or not press it properly...)

For a marathon I'll have the Garmin on one wrist and a pace band on the other.  The Garmin will be set to autolap and autoalert every mile (or every km in Paris!) and the display will have (a) time (b) HR (c) Average pace - lap.  Autoalert will let you know when to check your last split time - obviously this will not correspond perfectly to time between mile markers but will give you a good idea of whether you're, er, on pace.  Then simply check the time against the pace band at each mile marker to make sure you really are on pace. 

Simples.

21/03/2012 at 10:25
I thought GPS locations were only accurate to within about 10m anyway, so potentially your GPS could alwasy be 10m out at any position around the course.  Those would soon add up to a significant amount without you doing any extra distance.
21/03/2012 at 10:30
In 2010 my Garmin said I had run 26.6 miles, I was trying to get under the 4 hour mark but went over the finish line in 4h 3mins, the extra .4 miles took me over - GUTTED. I will be trying to stick close to the blue line this time
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