Question about Marathons, the wall, and the pace that gets you there. (Read 1290 times)

I recently did a 20 miler (my first ever!) in preparation for my first marathon. I got through 16 miles just a hair under 2 hours (literally, like 1:59:55) which was 7:30 pace. I ended up running 36x over the last four (and change) miles. Obviously I died pretty badly. I was wondering, why that happened though. 7:30 is probably a smidge faster than my "easy" pace, but I was feeling pretty fresh at mile 16, it was just I started struggling through mile 17, then had to start jogging pretty slowly. I was feeling absolutely fine through 16 miles, I would not have said I was pushing it at all. Now, that is probably not the kind of thing I want to have happen on race day. Is running a more conservative pace, like 8:00 mile, going to be a better idea? I feel like 8:00 isn't really any easier than 7:30 is, would I still end up dieing off 8:00 pace? I always hear people say, don't go out to hard in a marathon, but I don't see how different paces that are all still going to fit into your fitness as "easy" runs are going to have different efficiencies. Does what happened mean 7:30/mile is to hard of a pace for me to run, or did I just "hit the wall" so to speak, and it wouldn't have mattered if I was running 9:00/mile, that was where I was going to get really tired. I'm only about 5 weeks out from my Marathon, so I'll have maybe one or two more quality long runs in me, and I really want to know if running an even more conservative early pace would be a really good idea. If I'm going to die at 16-17 miles no matter what I'm running, I obviously would rather get there in 2:00 as opposed to 2:10, and then I have 10 minutes in the bank. If I could maybe get through the whole thing cruising at 8:00/mile though, that would probably end up being a bit faster. What I'll do is take my next long run at an easier pace and see if I blow up again, but I'd really like to know about this. What makes this even a little bit crazier, a few weeks ago, I did an 18 miler and closed the last two miles in like 14:30, with the last mile right around 7 flat. The pace for that run was overall faster than this one, but the pace through 16 miles was slower. Needless to say I'm a bit confused.

Is your log right in that you've never raced farther than a 3200m? OK basically - the faster you go the higher percentage of calories burned are from glycogen (carbohydrate stores in your muscle). If you train slower, you burn more fat for fuel than if you train faster. If you are going out too fast and crashing that hard you may have run out of glycogen. If you go out slower during the race you burn a little less glycogen and a little more fat every mile than if you go out too fast and you will last longer. Proper fueling also helps i.e. I can run 18+ miles in a training run with no carb intake with no problem because I will usually run 9:45-10:15 pace. In the marathon I ran 8:30 pace, but I did ingest gu.

Ya, I get that, but I don't see how a slower pace, like 9:00/mile, is any more efficient than 8:00/mile pace. You are going to burn the same number of calories/mile at those paces, and it seems like the engaged systems are almost entirely the same, staying as close to purely aerobic as you ever get. I just don't understand the concept of how one easy pace is going to be more efficient than another easy pace, or if that is even the case. I realize I haven't really done the kind of distance you would want for a competitive marathon, so I'm going to be relatively sucky over the last couple of miles, but I don't want to have to start running 9:00/mile pace if I can avoid it. It very well may be I just hit the wall at 17 miles and have to jog in, but if that is the case, I want to get there as fast as possible. Edit: Also, I've done 5ks (probably like 60 of them at this point), 8ks, and a 10k, but all that was before I started logging my miles. I've been running 13+ miles in a sitting semi-regularly (one to two times a month) for the last year, so I'm not completely new to longer distance runs.

What makes this even a little bit crazier, a few weeks ago, I did an 18 miler and closed the last two miles in like 14:30, with the last mile right around 7 flat. The pace for that run was overall faster than this one, but the pace through 16 miles was slower.

So, you have two runs. In the first one, you ran 16 slightly slower, then picked it up at the end and felt fresh. In the second one, you ran 16 more quickly, and then kind of blew up at the end. I could be wrong... and generally after a few more people jump in with meaningful responses I tend to be kind of wrong... but it sounds to me like that pace in the first 16 miles of the first run is the pace you'll be wanting to consider as your happy pace in five weeks. BTW, "the wall". You went from 7:30s to somewhere around 9:00s in the second run and it came on suddenly. Yup, you were tired. But my personal experience with the glycogen-depletion wall is going from 8:00 miles to something like 11s and 12s with walking mixed in. And then sitting down.

It very well may be I just hit the wall at 17 miles and have to jog in, but if that is the case, I want to get there as fast as possible.

Um, if you read examples of folks hitting the wall, they don't exactly jog it in. Proper fueling is key, as Ennay says. Same as for a car: Your burn more gas speeding than going slower.

Not for me. It has always been 7's then several high 8's and 9's before the 11's and the walking. If you'd given him another mile or two there would have been some 11's with walking then sitting. Is my guess anyway.

I'd buy that for sure.

Yeah. If I'm just a little fast, I'll go from 8's to 10 to 12 over a few miles. OTOH if I go out way too fast, the collapse happens earlier and very suddenly. Jacksonville '07 comes to mind

This is another reason why high weekly mileage is so good for marathoners. Because you are always running in a state of some sort of depletion you get really tuned into the way different paces affect you in terms of energy burn and your body learns (I think) to utilize various sources of energy at faster paces. When I was your age, like you, training for high school races, I couldn't have told you the difference between 7:00 pace and 8:00 pace in terms of feel. Now, having experimented with longer distances and higher volume training, I can feel the difference. Run 100 miles in a week, and 7:00 doesn't feel so easy any more. You can learn these differences doing long runs, too, but it just takes longer.

Okay, for the record, lactic threshold and marathon pace are pretty far apart (LT is roughly the pace you can hold for an hour). Both of which paces are only partially related to questions of fuel burning.