I've crashed and burned at the 10.5 mile mark of the half marathon twice now. Help me.

Going out too fast? Are you running even, negative, positive splits? Wrong course for the horse? Weather? Nutrition?

Need more info. What kind of pace are your LRs and easy runs? How much threshold work are you doing?

I've seen that 10 ez + 5k tempo mentioned a bunch here recently, seems nice on paper but is that the best thing for you? I don't know.

Do you do any progression runs? If not, sprinkle some in. Doesn't have to be finishing at HM pace, just helps you get used to picking it up toward the end of a run.

Any other race times other than that 18:38? I think based on that 5k you can run 1:25 if you get things right.

My splits are always really consistent. I hold back on the first 10 minutes and then really lock in. Literally 6:50 the whole way with the occasional 6:30-6:40 on a downhill. Weather has been close to ideal both times. Rest and nutrition have been great.

Get your long run up to 16-18mi. Make sure the first three miles of your half are a very comfortable pace that is a bit slower than goal pace. Most people crash in the half because they take the first few miles out too fast in hopes of banking time. Race a few 10ks. The second half of a 10k is similar in effort to the last three miles of a half. You need to be able to sustain 3 miles at what feels like an anerobic effort where you are huffing and puffing with every stride. Best workouts would be long intervals with a moderate rest interval. 4x2k with 1k rest in between, intervals a little under half pace. 3x3k with 1k rest in between, intervals right at 1/2 pace. 3x4k with 1k rest in between, intervals a little over 1/2 pace. Rest intervals should be faster and not easy pace. About 30-45 seconds under 1/2 pace. Goal is to feel smooth the first half of the workout and then going to the well the last interval.

The pace on LRs is an intriguing factor. It doesn’t jump out as being specific to the sub-90 HM goal, but doing some 10+ mile runs at 7:20-7:30 pace instead of 8:00 as the case may be could make all the difference.

Easy runs are usually 8:20-8:35 pace, with the occasional 8:45/8:50 if I feel bad. 2 hour long runs.

Did a few 2x2's at 6:50 pace on tired legs in the middle of 10 milers.

5x1 miles with one minute standing rest. (6:40, 6:35, 6:26, 6:26, 6:20) on the treadmill.

Did 20x400m at 6:13 pace with 1:00 walking recoveries (heart rate down to 120bpm)

5x1000 at 6 flat on the treadmill. No 10K races in my area to try, unfortunately.

Do your easy runs faster. You're crawling along out there, bud.

On your 15 mile long run. Go slow first 10 and then start grinding it out that last 5 miles increasing the pace 10 seconds each mile. You will be teaching your body to conserve energy the first 10 then gradually picking it up. How old are you? Good luck

Yes, my totally unscientific advice is to do more runs at something within 45 sec/mile of your half marathon pace. They don’t even have to be “long runs.” I understand your approach, but 2 hours at 8:30 pace or 20x400 w/ 1:00 walking are both less specific to your goal than simply going out and running 9 miles starting at 7:40 and progressing to 7:00. You’re trying to “piece it all together” too much on race day and beating around the bush in training, IMO.

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Basically this.

It's pretty normal to find yourself running out of gas in the last few miles of races this long. I'm assuming you are relatively experienced at shorter races, but these are your first few halfs?

You are just going too fast - it's really easy to do this because the pace (apparently 6:50) isn't that hard for you, so it is easy to lock in. But make no mistake, if you are cratering at 10 miles, then it IS too fast. I had the exact same experience in my first two half marathons, felt like I was absolutely cruising along until somewhere between 8 and 10 miles when I fell apart.

Try going out notably slower and looking for a slight negative split.

I totally understand. I feel like I save up energy for workouts twice a week, and a lot of my runs at 8:20-8:35 pace are at a heart rate of 135bpm. I've had a few weeks at 60 or 70 miles a week but then I'll have a 35 mile week due to obligations and travel, the so average of the training block will be 50 mpw.

Good stuff. Easy pace is okay but could be closer to 8:00 - 8:20. Take your recovery days as slow as you need, but your regular aerobic runs should be a pinch faster, especially at the end of these runs. Hoping your easy/regular runs are in the 1:05 to 1:20 range as well.

You should try some more traditional threshold workouts and try to get that pace closer to 6:30 and ultimately 6:20ish if you want to run 1:25, which again I think you are capable of.

6 to 8 x 1000 at 4:00 - 4:05/km with :45 second rest.

Also, I assume you are running road races. Try to do more workouts on the roads/track and less on the treadmill, for a bunch of reasons.

I figured that the KISS strategy might be most helpful to our friend here.

Without even reading your post or any of the replies, the most probable answer is that you're going out to fast. The answer to almost all "crash and burn" questions is that you went out too fast.

I can do a race in 5 weeks (Aug 31) and my body feels really good. I'm closing in on a 75 mile week, this week after taking a few days off. I'm willing to bet I can get to a few 80 mile weeks in leading up to it, and doing a half marathon on Aug 31.

So I need 4 weeks of training including this week to see if I can pull it off, with the 5th week being the race week. What would they look like?

Figure out your goal pace per mile - being realistic.

In your half, run:

1st mile 30 sec slower than goal pace,

2nd mile 20 secs slower that goal pace,

3rd mile 10 secs slower than goal pace,

from then until ii or 11.3 mi run your goal pace, then 100% race te last 1.5-2 miles.

This is a tough one OP based on this response. Your 5k gives you 1:25 half marathon potential. I would think you could break 1:30 with even pacing on a good weather day on 50mpw. Agree with what others have said. Think about some slightly longer long runs & adding in a mid week medium long run if that's not already there. The 4 x 2 miles is a great workout but is that workout normal for you in training or do you mostly do shorter/VO2 max type stuff & occasionally do something like that? I would look for 8k-12k worth of threshold stuff each week in a half specific build.

Some progressive long run stuff could be good for you. 90min long run with 60 ez/20 build/10 c/d. The build would be 5 @ GMP/HMP/T/faster than T. Something like that.Maybe think about fueling. People go in circles on that topic on here but I'm pro fueling in a half, even a gel around halfway + some fluids. Make sure you're eating enough pre race and race morning. Pacing is really important in a half. You said you're running at goal pace so I'll take that at face value. For a half, I'd rather be 5s too slow than 5s too fast early on. If 6:50 is goal pace, I'd go 6:55-7:00 through 1 mile & then spend miles 2 & 3 getting down to 6:50. Lock in through 10 miles then try to pick up the pace where you're currently fading.

Wouldn't try a ton new in the next 5 weeks. But 4 weeks @ even 60-70 miles would be fine. Run 6-7 days/week. 1 mid-week threshold session (you're doing 5 x mile @ T, let's do 6-8 x mile @ T, switch it up- 3-4 x 2 miles, 2-3 x 3 miles, 10-12 x 1k), 1-mid week ez medium long run (start @ 9-10 miles, build to 12-13) the day after, long run @ ~25k (ok to build a little more), then basically up to an ez hour on the other days. Tack on strides to an ez run or two.