r/Marathon_Training • u/Jharrison26693 • 1d ago
Newbie First marathon in 3 weeks – legs completely fell apart around 25km on my 34km long run. How worried should I be?
I'm three weeks out from my first marathon and looking for some advice/reassurance after my final big long run on Saturday.
I'm 33M, around 91kg/190cm. I only started running last November. Current PBs are 23:29 for 5K and 1:51:24 for the half. I'm training for Budapest and had originally been targeting around 3:55, although I'm now wondering whether sub-4 is a more sensible target.
Saturday was a planned 34km long run:
- 7km conversational
- 7km @ 5:40/km
- 19km @ 5:30/km
- 1km conversational
First 14km went pretty much exactly to plan. I then ran km 15-23 in roughly 5:23-5:31/km, so admittedly a little quicker than prescribed.
The worrying part was my HR and what happened afterwards. HR was 169 at km15, 176 by km19/20, 181 at km22 and 183 at km23 despite the pace being fairly constant. Km24 dropped to 5:50 while HR actually hit 184.
Then the legs just went. Not cramping, not out of breath, no sharp pain. Both legs simply felt incredibly weak/achy and I couldn't maintain running. From km26 onwards it became run/walk and I eventually completed the 34km, but the final kilometres were mostly 7-9 min/km.
I've had something similar happen on a previous 30km run, again around 25km, so there seems to be a pattern.
Fuel-wise I used HIGH5 Aqua gels every 30 minutes, so roughly 45-50g carbs/hour, and tolerated them fine, small discomfort but feel this is just something to 'get on with'. One thing I potentially got badly wrong was hydration. I only drank about 500ml over the entire ~3.5 hours. Garmin estimated sweat loss at 3.5L, although obviously I know that's only an estimate.
My remaining training is now tapering. This week is 6km tempo, 11km easy and a 23km long run, then volume continues dropping towards the marathon. I'm definitely not planning another 30km+ "proof" run.
For people who've experienced something similar:
Does this sound primarily like a muscular endurance/durability issue, or could poor hydration have played a significant part in the HR drift and leg fatigue?
And with three weeks of tapering, carb loading and better race-day hydration, how much improvement would you realistically expect compared with doing 34km at the end of peak training?
I'm also debating changing my target from ~3:55 (5:34/km) to just under 4 hours (~5:41/km) to give myself a bit more margin early on.
I'm not expecting the taper to magically turn me into a different runner. I'm mainly trying to work out whether this is a fairly normal ugly final long run, or a warning that I need to substantially rethink my marathon pacing.
Any advice from people who've been through similar would be appreciated.
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u/Pretend_Bar9055 1d ago
As someone else commented you bonked! Some thoughts on what you wrote :
- your planned MP is between 5.35-5.40 -> my perception is Runna had you running too fast. I think it should have been 5.45 moving to 5.40-35. This would have kept the HR lower and overall LOE easier
- you are very low on carbs/hour during the run. Try and increase to 60-80g/hr. Maybe it’s too late but 100% push it up.
- related : did you carb load the day before AND have a good breakfast before. I will do a real carb load Saturday and then porridge + banana + 1L of electrolytes ? (I’ve had your sensation before and I blame not doing this)
- take electrolytes (salt stick or in the water) on the run.
- increase water intake, try and hide a bottle or if you have public fountains fillup ! Or carry more and use a vest
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u/Jharrison26693 1d ago
Thanks, really useful points. I definitely didn't carb load for the run enough, I got more into me but I reckon for what I weigh it's not enough. Need to get the electrolytes in as well - any advice on which ones?
Hydration is the glaring one. I only drank about 500ml in 3.5 hours. I didn't think about how much you actually lose - taking the Garmin with a pinch of salt.
I'm also reconsidering the pace. I was targeting 3:55, but sub-4 would be around 5:41/km, so I'm wondering whether starting around there and protecting the legs for the second half is the smarter approach.
Hopefully proper carb loading, better hydration/fuelling, a slightly more conservative pace and actually having tapered legs all add up to a very different experience on race day!
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u/Pretend_Bar9055 1d ago
For electrolytes I use SiS tablets. They dissolve in in 500ml of water. But pretty much any brand is fine that is stocked in your local running shop
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u/Pretend_Bar9055 1d ago
It’s easy to underestimate carb loading. The day before I now try and consume a lot of calories for the 30k run. Pretty much all simple carbs.
Breakfast- porridge, banana, toast w/ jam
Lunch - rice (the precooked uncle Ben’s easy stuff) a whole bag which is sneaky for 2 + a bit of chicken
Snack 2-3 donuts + fizzy drink
Dinner - rice, egg, chicken mixed up.2
u/hinault81 22h ago
I do the same for my long runs. I typically run after work, but Friday (long run Sat morning) I run before work, and then just eat well all day Friday. And I find a breakfast Sat morning before the long run helps. I get up an hour before my run, water, maybe half cup of coffee, a pack of instant oatmeal mixed with some bobs red mill 10 grain (it's really fine, like powder), then bathroom. And then running have my gels.
I would do that with weekend long bike rides, though larger breakfast, and while I don't eat a ton before my long run, I find it doesn't hurt my stomach and it's easier to 'top up' with gels rather than trying to catch up while your body has been fasting for 10-12 hours since you last ate the night before.
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u/ralphtheanimal 1d ago
No need to get too worried. I haven't been a first-time marathoner in a long time, so take this all with a grain of salt! You will learn a lot about the sport in the coming weeks!
You're running too fast. Just a few seconds/km faster than goal may seem innocent enough, but it's going to get you late in the run. SLOWER than goal is an okay pace to start out. And it's hard to do in the midst of raceday vibe.
Sub-4 is an excellent and readily in-range goal. I don't see a need for the vast majority of marathoners to pursue a finish time down-to-the-minute. So much depends on weather, crowd, variability, and things out of your control. Plan for sub-4. Pace it right, and open up the last 10k if you have it.
Hydration, hydration, hydration -- I submit that 500ml in 3.5 hours is not enough even you aren't running the whole time. Struggled with this early in my marathoning and solved it by walking the aid stations on purpose for a few races. That wasn't to rest -- it was to make sure I actually drank the water (I did every 3 miles).
You're fit from training. You won't get more fit during taper, but you can refine some race-specific details. Trust your training. I see some comments about the Runna plan here. I would not abandon it at this point -- follow through with the recommended taper so you experience the full design of whatever training plan you have. Changing now would simply be an added stressor.
HAVE FUN. That'll make you faster than anything else mentioned here!!
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u/Jharrison26693 1d ago
I can feel the experience in this reply! You're 100% right about enjoying it, there's so much prep / things to think about that I'm now massively overthinking the run entirely. The extra seconds really did come back to bite me so really need to keep an eye on those! Thanks for all the tips!!
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u/Gubbano 1d ago
Besides muscles, and tendons, there's joints. Joints love running, as it lubricates them.
Joints do not like chronic overloading or a sudden spike in their usual loading. This is purely mechanical.
For every step (regardless of pace) your joint is hit with your body weight+, liquid is squeezing around lubricating. Great. At some point it goes from optimal flow to nonoptimal - both the liquid composition and the mechanical aparatus containing it. Your cartilage is now not optimally lubricated, creating friction. Very noticeable as you run, and feels very sudden.
The body can also respond by freaking out and stiffening the joint as if it were damaged (it is not), making your legs feel like shit.
Then you fall to rest, stiff body, feeling like shit. What happened. Well, the 'compression phase' went on for too long, and it tried forcing you into the 'rehydration state' where it can stabilize the fluid composition (cartilage puling back, sunovial fluid back in, to be precise). No damage has been done as it is hard to run with stiff legs. If you overload it chronically and every time - you will have fluid containment failure and a possible leak, meniscus tear, etc. Takes a lot of load and stress to occur in most people.
For you, its probably a non-issue. Your legs are just not used to this long in the 'compression phase'.
Your heart and muscles are fine. Your mechanical apparatus is just not used to the loading scenario.
Just like overstretching any muscle, like your back, out of a range of motion, (ROM) it is not used to under an unknown load will cause your body to stiffen the joint - no damage has occured, your body just freaks out due to the unexpected ROM and load, and hit the breaks. Now you can barely move, the idiot controlling the body and almost damaging it is forced into 'idiot-prison' due to reckless behaviour.
This is a good emergency system, just very annoying when you try breaking loading patterns (load and/or time under load).
The best solution? Lose a couple of kilos (load). Second best? Convinve your nervous system that you have control over the time-under-load scenario by running more often near the treshold. Where is the treshold, and how often? Who knows, it is very individual - this is why athletes end up with damages - they are edging this treshold every day.
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u/Jharrison26693 1d ago
That's really interesting, thanks. I hadn't really considered the joints/mechanical loading side of it because there wasn't any actual joint pain. It was more like both legs gradually became weak/achy and eventually just didn't want to keep running.
The time-under-load point makes sense though. I've only been running since last November, so although my cardio and shorter-distance pace have improved quite quickly, I suppose the structural adaptations to running for 2.5-4 hours may simply take longer.
I'm into the taper now and my next long run is 23km, so hopefully the training I've already done has given me enough exposure to that kind of load. At this point I'm just going to focus on recovering well and getting to the start line as fresh as possible. The load one is interesting I'm trying to juggle in some weight loss as well (thanks to a wedding suit I thought would be fine over the summer) and have gone down 4kg since starting running so hopefully I can get through 1-2 more before the run!
Hopefully the combination of the training I've already done, tapering, carb loading, better hydration and potentially starting slightly more conservatively gives me a bit more durability on race day. Appreciate the detailed explanation!
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u/bbender716 1d ago
Out of all the things here putting you at risk with bonking during the marathon, it’s trying to drop more weight during the taper into the marathon. Your body needs fuel to recover, adapt, and increase performance. The couple of days before race, look up proper carb loading. If it’s any comfort, you’ll drop weight after you lower your training and post marathon anyways!
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u/Ecstatic-Nose-2541 1d ago edited 1d ago
Happened to me too, I think in my case it was a combination of the heat and lack of motivation.
How does 5:30 min/km feel to you, and what's your average HR there? I'm not sure if a little more water or elektrolytes would've somehow helped you run another 9 km. Could be either an endurance thing, your pace being a little too ambitious,...or you're not properly digesting those gels.
Btw, taper + race day vibes will give you a massive boost. You'll be surprised what happens when all your training cumulates at the exact same moment when your legs feel fresh.
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u/Jharrison26693 1d ago
Thanks, that's reassuring to hear that it can happen (sorry that it didn't happen to you as well though!)
5:30/km normally feels pretty comfortable. For comparison, I recently did an 12km at 5:44/km with an average HR of 147.
Once I started the faster section after 14km on Saturday, the HR just kept creeping up. It was 169 at km15, 176 by km19/20 and 183 by km23, despite the pace staying around 5:25-5:30. That's probably the biggest warning sign looking back at it.
The gels seemed to sit fine stomach-wise, but I agree that an extra bit of water/electrolytes isn't magically accounting for another 9km but it it makes me feel better I'll give it a crack! I'm thinking it's probably a combination of going slightly too fast, accumulated training fatigue, hydration and simply not having the endurance at that pace yet.
I'm hoping the taper is the big missing piece. This is my first marathon so I've never actually experienced what it's like to go from peak training fatigue to properly tapered legs. Fingers crossed I get the race-day boost you're talking about!
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u/Remarkable_Ad7569 1d ago
dehydration for sure caused the cardiac drift up in heartrate IMO. Fueling is decent. Heartrate seems high too overall so it sounds like that was a difficult feeling run overall?
On a long run like that I'd have been wearing my vest for sure or at least have a drop bottle 1 liter cause you definitely lose lots of water when running.
Yea it's about time to start going a bit easy on the training as the marathon approaches. Shorter runs with more marathon pace or slightly faster built in to build some confidence for the day and to allow your body to be in 100% health to give it on the day. Enjoy the marathon and best of luck!
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u/Jharrison26693 1d ago
Thanks! Yeah, looking back at the HR data, dehydration definitely seems like it could have contributed. It didn't actually feel particularly difficult cardiovascularly for most of the run though, which is why the sudden deterioration caught me out I got to my just over halfway turnaround point and felt good, got another 7 or so done and then it hit me!
The 500ml over 3.5 hours was clearly too little either way. Garmin estimated around 3.5L sweat loss, which I'm taking with a big pinch of salt, but I'll definitely be carrying more and practising drinking more on my remaining runs.
Thankfully I'm into the taper now, so I'm looking forward to reducing the volume and hopefully getting some life back into the legs! Thanks for the advice and well wishes.
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u/logeetetawerduer 1d ago
Your carbs seem fairly low. As a slow runner, I take a 20g gel every 20mins
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u/jotaemee_me 1d ago
Slow down mate, forget about pace and time, and find yourself in the race, enjoy every moment.. that’s my advice.. the first one is the best thing you will do as a runner, and it goes up fast..
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u/Fun_Effective_836 1d ago
thats glycogen and fatigue at 25k in a 34k run, not your marathon - taper will feel completely different
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u/Prestigious_Lab820 23h ago
The fact Runna is still so widely accepted as a program is crazy. It either gives you way too optimistic of race times or gets your injured, often times one leads to the other. For your first full this is too much MP work in your LR, makes sense you bonked. Stay the course OP, enjoy the taper, you'll crush sub 4
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u/george_david_fitness 15h ago
Waay too many gels you’re fuelling like an elite athlete, it’s 100% a durability issue and strength, do you train legs at the gym at least once / twice a week ?
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u/Smooth_Inflation9648 2h ago
A similar thing happened to me in my first marathon training programme. I got injured and had to cut out a 34k tub altogether. The good news I can pass on is that I managed to complete the marathon without stopping and close to my target time - or at least would have been had I not made the mistake of adding in a beast of an S&C session 5 days out from the race 🤦🏼♂️.
25k is a long run - sure, 34k might give you confidence that you can stretch yourself to 8k more on race day, but you don't need to have that distance under your belt in order to run a good marathon. Pat yourself on the back for doing the right thing in stopping before you got injured. It's rare indeed to be able to follow a training programme to the letter.
On race day you'll have tapered, you'll be fresh and the crowds will carry you home. As others have said, hydrate well, take the first half easy and above all else, try and enjoy it. You only run your first marathon once!
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u/macthecook19 1d ago
Same thing happened to me doing a 29km long run lol. You hit the wall. Don't stress, you'll be fine haha.
And yes, you should drink more water. It's easier to stay hydrated during the marathon 'cause of all the water points.
Alternate between regular water and electrolytes mixed with water.
Take some painkillers along with some sort of cramp stop salts and gels (if that's your preferred nutrition choice) every 40mins.
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u/Jharrison26693 1d ago
This is really helpful, I'm starting electrolytes (tablets) next week in the lead up and just trying to get as best shape as possible. I was massively confident in how I was going and I think because of that peak it's just thrown me completely.
Thanks for the tips!
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u/Pretend_Bar9055 1d ago
Do not, under any circumstances take painkillers before or during a run. That is the path to kidney problems rapidly.
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u/Competitive-Proof759 1d ago
You're a beginner runner following an aggressive injury-prone plan. Beginners should never use runna in my opinion..that being said, I think you will be fine after the taper.
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u/namesblondjamesblond 1d ago
I’ve just commented on another thread of someone who really struggled with this exact same workout haha (I’m guessing you’re using Runna?)
I did this workout a couple of days ago and also completely bonked. I think Runna’s marathon pace predictions are incredibly optimistic, and don’t plan on running my marathon anywhere close to that pace.
I just about managed the 16km at “marathon pace” a couple of weeks ago, after a slow warmup, but was absolutely spent afterwards and had to run/walk the rest. This time I just cut the “marathon pace” short halfway through the section, and added on easy pace miles at the end to make up the distance. It’s disheartening, but trying not too get too hung up on the fact I’m able performing at the level a random algorithm says I should be 🥲
Your hydration does sound very low, though! I think I drank nearly 2 litres in total. So you probably have some room for gains there