Please, somebody put me out of my misery and tell what I’m doing wrong in the marathon.

As I guess you're not a pro athlete I'll add a thought for you:

An 18 week plan might be too long.

Next time try to get in good 5k-HM shape. Forget about the marathon.

Then take a couple of days completely off. Then start easy a couple days. Then do a 10 week preparation. In this preparation you do at least 6 runs of 20-22 miles until 2 weeks out. Even 1 week out you run at least 15 miles.

It might be that the long focus is tiring you.

When you are in 1:26 shape you do not need 18 weeks to get to 3:15 fitness. Normally u should be able to run 3:15-20 any day that ends with "y" with 4-6 weeks prep.

Have fun, sprinkle in some 15-18 mile jogs even when Training for 10k/HM. You'll 99 % get at least down to sub 3:10.

Pikachu

Correct me if I'm wrong, but I think we use different terminology. It looks as though your 32km took place 3 weeks out, your 24k was 2 weeks out, and your 19k was a week out (e.g., "4 weeks out" is roughly at the start of the week).

TL; DR: That's too much to recover from. No wonder you blew up.

So your goal pace this time around would've been 7:26/mi. Depending on weather, I like your 8:34 easy run for a 36km long run; that's in range. In good weather, I think a few miles around 8:45 to warm up would be good, then just a nice progression to whatever feels easy, but on an easy day, probably not going below 8:00/mi. Just get fat-burning and glycogen storage adaptation those days (with other adaptations) and save yourself for workouts.

I think the idea of a workout might be ok for the other one, but I don't know why you're going "from just slower than MP to faster" in one of your longest runs. I've never done a high-volume workout in one of my two longest runs. And even if you do so, why would more than 65% of it be faster than easy pace? Did you have any miles well above 8:00/mi that day?

I'd put the HM 5 weeks out instead of 4, and I'd skip the workout the following week, especially if you go faster than easy in the following week's long run.

So 19-14 days out, you did 10x1600 near MP, then a sub-40 10k, then a long run workout on Sunday? If you're doing 24 km with 4x5km at MP, that's with no warmup? I would expect your legs to be trashed, and I would expect the effects of that to linger for a while. If you could do all that in that week, I'd expect that at your current mileage, you could run no worse than 3:10 if you were to quit wrecking your legs close to race day. Probably a good bit faster.

I think this is good advice. Last year, I trained for a marathon, and put together an 18 week training schedule. I think I hit my peak fitness about 10 weeks in when I ran a half in preparation. I stagnated from that point on and think I showed up to the marathon tired and a little overtrained. Looking back on it, I was already in great shape (for me) when I started the block. It was too long, and marathon training is a grind...

I do a minimum of 6 runs of 33KM or longer before a marathon. Two per month with the last one 3 weeks out. I sometimes stretch then by up to 2 KM so that by the last one I am doing 40+KM. It seems to me that your long runs are too short. BTW. I don't do more than 2 runs of that length in a row. My personal experience is that once I tried that 3 weekends in a row and the second weekend I couldn't believe how much better I felt compared to the first weekend but the third weekend was a disaster so I don't do 3 long weekends in a row. BTW. Did you taper correctly?

I second this interpretation. Your training plan looks fine, you have done enough mileage for a 3:15 and enough long runs. Plenty of people breaks 3 with 40 miles/week and three long runs over 20 miles. You have done a lot more than this.
The problem might be that you have peaked too early and, when marathon day comes, you are already on a downward trajectory fitness wise. I find it telling that you did not really "bonk", but just gradually slowed down and were unable to keep the pace. If I were to change anything, it would be try a shorter marathon buildup plan.

Sorry, my bad: you are correct regarding the weeks out.

Thanks for posting, a lot of interesting points to consider. I did wonder at the time whether that week was a bit much but I seemed to get through it with no ill effects so didn’t think much more of it. I had a pang of regret reading your post. I will definitely be more cautious in the final month next time around.

I think you made a few mistakes:

1- Training too hard too close to the marathon.
2- Letting work stress impact your performance. Work stress is the same as training stress. If you are in the type of job that is just so stressful that there is no other way, in your next marathon build-up, take a week off (if possible) before race day and go on a vacation with the family.
3-Like others have said practice running long on an empty stomach every other long run and only use a gel if you bonk (in training)

You're training way too hard !

The marathon is an aerobic event. Your 32 km 4 weeks out was way to fast. I'm a 3:04 marathoner and I ran 32 km at 5:00/km (8:00ish a mile). You should've run the 32 km at about 5:10/km (8:15ish a mile).

3 weeks out: what a week: 10x1600 faster than MP, a 10 k race and a long run with 4x 5 k@ MP. WTF ? You should've done only one of those three at most.

And why not doing the long run at easy pace ? Why the need to run so many miles @ MP in your long run ?

Very interesting thread and a lot of great input so far.

I had a similar problem. For years. then I realized I could not prepare for a marathon the way I did for halfs, 10k's, etc. I needed to eat! So, 3-4 hours before the start I ate a bagel with peanut butter. it made a huge difference.

It looks as though you're receiving a lot of the same cliche advice ("you went out too hard", "your training block was too long", etc) from people who obviously don't have the same problem, and who ultimately don't get it.

I also struggle with this. I'm doing a half on the weekend and hoping to run around 1:21-1:22 (which would be conservative for most, as I just ran 16:49 for 5k). I've never broken 3 hours for the marathon though, and I doubt I could if I switched from the half this week.

Initially I thought it was that I just needed to do more mileage, but I've seen and know many, many people who've run much faster than 3 hours off half the mileage I did for my last marathon block, who also have much slower PRs at the shorter distances.

I've come to the conclusion that it's a combination of a couple of factors: biomechanics and metabolism.

When I say biomechanics, I don't mean that I run with a super-inefficient gate; but my theory is, that when my muscle elasticity begins to break down, my hips and spine begin to slump, and the transfer of forces do not remain vertical throughout my skeletal frame; which ultimately results in a shortened less fluid stride. This doesn't seem to be a factor in the shorter distances, and is only a small issue in the half (fingers crossed for this weekend).

I also think that I burn carbohydrates at a rate of knots - and can't replace them quickly enough.

I don't know for sure if these are the cause of my inability to translate my times to the longer distances, but they're my best guess.

You’re right that there are differences among people that can make the ostensibly obvious answers useless. But we all have to rule out possibilities in order of their likelihood. After the first post or two, there wasn’t quite enough info to tell whether OP was an outlier or someone who fell prey to a common mistake or two.

Now look at OP’s training from 2-4 weeks out, along with a few other details. That looks like exactly the sort of work that would make most marathoners lose their legs in the latter stages of the race. So I’d definitely go with having him correct that smallish set of training problems as a first step.

A 39:09 10k is pretty spot on equivalent to a 1:26 half. I mean if you maintained exactly 39:09 pace you'd be around 1:23, so kind of crazy that you'd expect their half to be much faster than a 1:26. Jack Daniels Vdot calculator says the 10k is equivalent to a 1:26:38 half and Vdot is notorious for favoring the longer distances too.

When you look at the workout 2 days before that 10k, you realize it’s even tougher to get a read on exactly how fit OP has been recently. That’s even before considering track vs. road, weather, what the schedule was before the half, etc.
n

You won’t really get a perfect apples-to-apples comparison, but im not sure about any of these. I like to compare trained for the distance + tapered + similar weather/terrain before extrapolating.

I cant believe anybody would try and do 3 hours of intense exercise without eating anything. And even now you are still only eating a single bagel? Have a proper breakfast!

I did a team adventure race with a friend, the whole thing took about 6 hours. After 2 hours he had started to slow down but usually he is about the same speed as me when doing half marathons etc. it took a while for me to figure out the problem, he said he had only had a couple of pieces of bread for breakfast 😧. this guy had done ultra races before so i have no idea how he survived in those if he wasnt eating properly.

It's common sense, if you are going to be burning thousands of calories, you need to eat a similar amount of calories before and during the race. Otherwise your body will have to use fat as fuel instead of carbs/glycogen, which is not efficient enough during a hard/long aerobic workout - you will be forced to walk to the finish.

3-4 runs at least 20 miles on a 12 week build up was my breakthrough.
I never ran more than 55-60 miles per week. Usually 50-55.

One key run was 4.5 mi warm-up, 13 miles at MP, 4.5 cool-down three to four weeks before marathon. Very little time between warm-up and MP session.

Had to be honest with MP and how hard I was pushing.

I’m a fan of lots of paced miles.

10x1 at mp

5x2 at mp

4x5k at mp

etc

repeat until they get easy.

LSD has been very disproven as effective when compared to quality tempo efforts.

more gym work required, you need a stronger core. or if no access to gym, pushups, pullups, some swimming etc.