Probably just an off day and maybe no fuel in the tank.

I've had days like that, where we are running our normal pace, and after a few kms I just feel drained, like I would if I hit an energy knock on the bike, etc.

Try again on another day, maybe eat a decent small breakfast before heading out. For me that would just be a pack of instant oatmeal and a coffee. :)

Have you run 5k's before? I hate, but at the same time love a 5k, and there's a pretty fine line that you need to ride (and not go over) in order to do well. A general rule I use is go our out hard in mile 1, try to maintain in mile 2, then dig deep for that last mile (this one obviously hurts the most), then sprint that last bit. I've used this strategy to PR and also blow up. It hurts a lot and there is some mental strength needed to push through. Also, if you haven't done that much training at 5k pace the wheels can come off. When I set a 5k PR a few years ago I focused on that distance from September to December, doing a track or treadmill interval session every week with a tempo run and a long run. I was also looking to PR a half marathon a few weeks prior to the 5k, so not optimal for either, but both races went pretty well.

I think it would be a lot easier in a race-like environment to do your best - solo efforts are hard when there's nobody else to key off or chase.

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EVERYONE has had something like this

Anyone who says differently is selling something

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"What's your claim?" - Ben Gravy
"Your best work is the work you're excited about" - Rick Rubin

Oftentimes you won't really know where your limits are until you go a bit past them.

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This ^

A 5k solo time trial is a totally different event than a 5k race against other people. The motivating your self to finish out the suffering in the solo TT is going to be 10 times harder than in a race.

The same goes for the 20 min FTP tests. They are intended to be solo efforts and not your best 20min power from a race. They're the biking equivalent of a 5k TT.

Happened to me on a half a couple of years ago. Was going great, feeling good and then just after mile 8 - boom. Legs wouldn't go. I finished by walking and shuffling 50/50 the rest of the way. I figured it was an off day where I went out faster than my body would do that day.

Since then I've strictly worked on negative splits. Last 5k (about 3 weeks ago) I purposely ran slower for the first mile than my goal, ran the second mile at my goal and finished the next .75 miles faster than my goal and the last .35 miles at a max effort. Finished 18 seconds faster than goal. For 1/2 marathons, I've beaten my goal by several minutes doing this. It can be a little nerve racking when I'm 2 or 3 minutes behind my goal half way through a 1/2, except that I don't feel like I've really run 6 or 7 miles. I feel like I've only warmed up. I'm really happy doing it this way and finishing strong.

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Not a coach. Not a FOP Tri/swimmer/biker/runner. Barely a MOP AGer.
But I'm learning and making progress.

I could have written the exact same post.
I do 5k tests every now and then and sometimes I start feeling fine but then realise that it gets too hard and I call it a day. When I repeat the run a few days later it's usually fine and I can have a good run. I don't know why I just stop. Probably I am not as motivated as in a race and also, since it is an all out test for me I leave no margin for error. In a race I would usually hold off a bit until later in the race. Have never suffered an injury or faced other negative consequence of quitting early.

Good luck.
Uli

Yeah, I think this is what's going on too. When the effort gets really hard solo, the voice of the central governor telling you to stop can be overwhelming. This is much less likely to happen with the additional adrenaline and competition in a race.

I ran a marathon this spring by myself, and intentionally did it at below-race effort for the first half. The last half still got tough and my pace still slowed a bit, and there were times where I thought about stopping to walk. Had it been in a race context, I probably would have run the last 6 miles 30"/mile faster and I would have been soaring on the energy of chasing and blowing by runners who were fading. Solo efforts can really drift from what you wanted them to be -- I usually have experienced this as cutting an interval set short or reducing the target speed rather than abruptly stopping, but I think the psychology is similar.

Thanks for all the responses. This is what I love about this. Setting a challenge and dissecting what’s happened to get better.

I think the pacing and fueling need to change.

I ate nothing prior. I think a gel or two would have made a big difference

Also, the negative split strategy is something I’ll try on this. Ironically on my solo marathon I crushed this and ran my second half 2 mins faster than the first.

I love the “pushing to the limit” aspect of the 5k.

I know - and I'm sure other folks around here know - people who have done marathons in the 4:30-5 hour range and say they won't do 5Ks because "they hurt too much"

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"What's your claim?" - Ben Gravy
"Your best work is the work you're excited about" - Rick Rubin

Sub 19 was your "stretch goal" and you started out at 18:20 pace.

When you're running 5 km on the rivet, even 5 seconds/km (8 seconds/mile) is a significant pace differential.

As others have alluded to, there's also a big difference between solo and running with others. And a difference again compared to racing against others.

You really need to get yourself on a track with some competition if you want a proper measure of what your capabilities.

Yup, i’ve had it happen on solo runs and in races. Like someone said in one of the replies, some days you have it and some days you don’t.

Also, your first few miles were faster than your goal pace, which for a 5k pretty much guarantees your blowing up in the last mile. I learned this one the hard way in a local road race years ago where I went out harder than normal and was feeling good, staying close to the front pack (which was rare for me) so I continued to push harder through the second mile to stay with them. Completely blew up with about a half-mile to go as they picked it up and I literally shuffled in the rest of the way, frustrated and pissed at myself.

5ks can’t be a total balls-out effort from start to finish. Going out hard but staying on your target pace is key where you’ll have something left to empty the tank in the last mile.

Hope this helps, good luck!

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"You can never win or lose if you don't run the race." - Richard Butler

^^^^This.

Next time try a 6:20, 6:10, 6:00 negative split (should be very doable based on the previous effort). From there speed the early miles (ex. 6:15, 6:05, 6:00), and you can progress to straight 6:00s.

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No, I’m not being judgy, but I’ve never had this exact feeling, and certainly not with that “little” left in an “interval.” Certainly, I have bonked. But this doesn’t sound like a bonk. Certainly, I’ve had days where you just aren’t as fast. But, he was on record pace. Certainly, I’ve had days where I’m not as motivated-again, not likely as he was on record pace for a fairly long amount of time. But, this one is puzzling-I’ve never had a day where I was on PB pace and then just completely shut it down with less than 25% Of the interval left. Again, I’m not judging, but this example is bizarre. And, I can’t pin it down.

Similar issue when I tried a 13.1 test earlier this year. I was feeling really good about my fitness and wanted to try and PR the distance on a beach trip (flat land).

Won't go into paces because compared to yours, well I'm a sloth, but I went out very similar to you at a bit faster than my old PR, with the hopes of maintaining and then digging down for the last 3-4 miles. I made it 7 miles before I had to take a walk break. Pretty much bagged it after walking for 60 sec and pulled back the pace to finish the distance with a few more 60 sec walks (had to, only way home).

Looking back, the wind didn't help, had about a 7-8 mph headwind, but when I flipped a U turn to head back, NO breeze anymore, even my movement, was like running in place on a calm day. I really thought I could hammer it and hold on based on my training up to that point, but I think coming out slow and then building would be the smarter play.

Maybe try it on the treadmill. I find some solace on the treadmill knowing that I can stop at anytime.

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https://www.strava.com/...tes/zachary_mckinney

Cant say that I have either. I've never been out on a tough run and one second be running PR pace and the next just stop. It's always a gradual decline to a slower pace, but never a full blown stop.

I do remember reading in Matt Fitzgerald's book How Bad Do You Want It where he talks about Jenny Simpson having a meltdown like this at the 2009 XC championships. It was an interesting account on her part about what went on in that race. Worth the read.

I’m with you. I’m just fascinated by what happened. My legs were “fine” it just felt like an involuntary body signal that made me stop my watch and shut it down.

I was talking to my son about it and he says that I should try again next week but take two gels beforehand and run at the same pace to see what happens. I think I’ll give that a shot to see if it was purely nutritional or if pacing was a factor too.

The 19 goal was based on a couple of intervals I had done in the few recent weeks so it wasn’t tremendously scientific.

If nothing else I now can say that I pushed it to the absolute limit today.

Now the quest to truly see how to maximize the 5k performance (minus the specific training) begins :)

I think that is the correct plan, couple gels or whatever. I really don't think its that hard to explain what happened, I've had several 'bonks' on the run and bike over the years, sometimes they come on slowly where I start feeling chills, other times it can be quick.
I'm betting 200-300 cals and a coffee 30 minutes before your next attempt, and you'll have no issues.

I'd say this is a normal 5k.blowup.

5km blowups can feel different from half marathon blowups depending on your leg fitness. Your legs might be able to go record pace but your hi end cardio my justnquit on you in the 5k even if legs.are all there.

I'm longer races you.more.often get the slowdowns and even death shuffles. 5ks.are too short for that unless you are really not trained for it.

Even sprint Tris are long affairs compared to 5ks.

You lost to the other you.

Ha! Exactly. Somehow he took over the controls for my right arm, moved it to my left arm and stopped my watch and then my legs.

Running a 5K at that limit is definitely more of a challenge than one might think... I recently bonked on my own 5K. The day before a friend called and said he was around did I want to get a drink... three beers later... I headed to bed late. Part of me feeling like garbage I blame on the day before.. but I had a great time socializing so not a total loss.

No time to really eat before the run, up early and out of the house... met two runners at a local track for a July 4th 5K attempt. So some coffee and banana plus the fact I didn't feel hot from the few beers the day before. I'm 46 and as I've gotten older I just don't feel very 'quick' or good if I've had more than a beer the day before.

We go out and first mile is 5:21, my second mile is 5:42 as they stay on pace and then I died at 6:07... finishing 18'sh well back of them. My friend said my breathing was pretty hard on the first mile and honestly the first mile was too hard for the way I felt. If I had gone out 5:45'sh maybe my legs would have come on?

I just felt awful. Day before I shot myself in the foot, got to bed late, didn't feel great the next day, didn't fuel well pre-run, etc.

Running a 5K is a challenge for sure, IMO you just can't bang out three (point 1) if you're not in a good state. Especially if your goal is at the limit of your speed/fitness.

It definitely sounds like a central (i.e., brain) shutdown rather than legs or heart/lungs and there’s lots of cool research, but still poor understanding, on our central governors. Sometimes it’s less about the absolute signal and more about the rate of change. Maybe the brain just felt your body was getting hot at an unsustainable rate and just said stop immediately. What I find fascinating is that some people seem able to disregard those signals, sometimes resulting in astonishing physical performances and sometimes resulting in disaster up to and including death.

I definitely agree with the sentiment that a grueling marathon including a bonk and death march is still way less painful than a 5k. I respect 5k like crazy, but doubt I will ever love it.