Sounds like you may have bonked.

What does "nutrition is good" mean? How many calories per hour did you consume on the bike. Did you eat during the run?

I never eat on my runs. I had a 24oz Gatorade and water before I ran.
I ate a bagel prior to the bike then 3 Uncrustables and a full 24 oz Gatorade / water during bike

Yeah. . . you bonked and/or got dehydrated (probably both). Did you get lightheaded, vision blurry or some such symptom. That's what happens to me. I'd suggest that you sign up for the saturday app- free for 2 weeks. It's eye opening how much nutrition you will need especially with a 1 hour-ish run after.

Is this your first IM? meaning first set of long bricks?

For example. Today, I rode 3 hours at slightly below IM pace. Ate 1000 liquid calories (in 72 oz). Ran a brick 4 miles (ate 100 cals/ 10 oz) and I was slightly under-fueled and got weak/lightheaded.

Ok will check it out. No , raced IMLP last year.

Yes , was dizzy and puked a bit once home

To the first, mental strength does not get you past your fitness. My best races ever were also the easiest mentally. In training, there are plenty of days you have to suck it up a bit, but that should not happen that often.

How much are you actually running and how long are you long runs? Plus, I would never do a run that long after a ride in training. Running poorly after a ride in a race is either a) poor pacing b) lack of run fitness c) poor nutrition strategy. D) all of the above.

When you go past about 90 minutes, you have to have a good nutrition plan. My stomach does not like mixing exercise and eating. The guy above who said he had 1000 calories in three hours made me want to vomit. I tried a little of everything over many years and I'm lucky to get down 100 calories an hour. I finally gave up any sort of racing that required eating.
When I rode up Mauna Kea in Hawaii last year (13,800 feet from sea level) I managed to get down about 1000 calories in the form of rice cakes and rice krispy squares over the course of the first six hours. That was after a summer of climbing and training my stomach to accept them. My best ever half-IM I did on about 40 ounces and 400 calories because my body was just super full of muscular energy that day. The other ten or so I attempted end in some sort of dnf or stomach shutdown.

I still like to race long gravel events, but I don't finish them strongly because at 4-5 hours of effort, my stomach tells me it is done.

To clarify My 1000 calories included the run so really 860 cal in 3 hours of biking and 100 on the run . One of the things that I noticed is that as I became more fit, my HR has come way down. In the past at IM pacing, I would be riding at a heart rate that was on the upper 1/3 of zone 2. Now I am in the lower to mid HR. As a result I think this has allowed me to tolerate nutrition much better. I also get a little nauseated at hour 4-5 of the bike and have some trouble with the sugary component of sports drinks which limits how much I want to drink. I Am planning to try something more bland like sustained energy which has no taste at hour 4-5.

I've also found that gatorade has too much osmolality (330 osm) for me which seems to shut down my gut and I tend to do better with more isotonic drinks.

Perpetuem/Sustained Energy got me through my only two or three half-IMs that were not DNFs or complete disasters. Gatorade=nauseous after two or three hours and no eating for another six hours while my stomach sorts itself out.

My 1000 calorie effort on Mauna Kea was possible because my effort level was relatively low--basically climbing at 150 watts for seven hours.

Ouch!! That's brutal!!

yep, my guess based off what you've written here is that you're underfed and maybe a bit dehydrated. that non-specific feeling of being 'body tired' and having low motivation - even if your legs themselves are OK - if for me a sign that i need more carbs on board. or that i'm just over-reaching.

might be worth experimenting a bit. the last year or two i've jacked my carb intake up a LOT on in training and i like it. my belly tolerates it well, energy is more even, and recovery is a lot quicker. in my case i target about 100 grams of carbs per hour (at most).

can't overstate the impact that this has on mood - when i'm bonking i'm not just tired but bummed out, and carrying on feels not just difficult but sort of pointless.

a general rule of thumb that seems to work OK for me is that if my heart rate is too high for a given effort, i'm low on fluids. if it seems too low (and i can't raise it), i'm low on carbs.

good luck!

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https://lshtm.academia.edu/MikeCallaghan

http://howtobeswiss.blogspot.ch/

“ I finally gave up any sort of racing that required eating. ”

That is a wise strategy. That’s usually my philosophy as well although I’m doing a half IM in a couple of months after 15 years of not racing anything longer than 2 hours.

The app by the name Saturday takes all the guess work out of this

It is the creation of one of the members here

Pretty much the same for me, but mainly because I've given my body a fair pummeling over the years.

It's a shame, because that sort of racing combines two of my favourite things.

This is my experience:

To properly fuel for long course racing, you need 4-6 calories/kg/hour on the bike (70 kg would be 280-420 calories per hour). It doesn't matter how you get it, just that you do it in a way that your gut tolerates.

If you fuel the bike properly, running should only require 1-2 calories/kg/hour (70-140 calories per hour).


When I raced I would mix up 20 ounce water bottles with about 400-450 calories of electrolyte drink in them and consume four of them on the bike portion.

Run, I just drink coke and water at every aid station (walk the aid stations so you can get the fluid/calories in).

I never supplemented with salt or anything beyond what I just described and I always finished with good energy.... (well, except for the fact that I was exhausted from doing an IM)

Racing is hard and everything gets unpleasant. If you stop taking in your calories because "It got too sweet" then you don't have the mental toughness to embrace unpleasant things. By the end of the race you will hate the taste of everything. You will hate your bike. You will never want to run again. IM is hard.

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Jason
None of the secrets of success will work unless you do.

Though I'd say it's perfectly fine to just race shorter distances and not "embrance unpleasant things." I like a good Olympic-distance race. And focus "mental toughness" on more high-end speed, legitimately fast running, and other skills rather than "enduring crappy sweet crap."

Fair :-) and agree. Except shorter isn't necessarily easier. I think one of the hardest (most unpleasant) things that I ever do is a well paced 5K. The agony of being right on the physiologic edge for 3.1 miles hurts more than an IM marathon.

I'm just always a little perturbed when people say they stopped taking their nutrition because, "I couldn't stand the taste of sweet stuff any more."

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Jason
None of the secrets of success will work unless you do.

Heat is a great instigator for blowing up, in addition to bonking. If you plan on 10min miles and it’s “hot” (which is relative to you), you will blow up at around those miles. As you ride you receive some cooling, but you body core temp is still rising. Once you get on the run, the cooling effect is much less, especially if there is no wind or you are running with the wind. Your body temp will increase even faster if the perceived effort is the same as the bike. That’s where the dizziness comes from. Low sodium, dehydrated and increased body core temp.

But that Saturday app has also helped me a lot. I still blow up sometimes on hot threshold interval runs, but it’s less now. (I’m just a satisfied user and nothing else).

But bonking can also occur at around the same time. Not fueling on the run after the bike, mixed with blowing up, and you have a great recipe for bonking. The problem with not fueling and being over heated is it’s hard to tell if you bonked or if you blew up. Only experimenting with your run pacing will tell you. Reduce your pace, but don’t increase you expected workout time and see what happens. If you still have to quit, you’re probably bonking. If you can do the run workout, then your probably blowing up because of heat.

YMMV, but this is my personal experience.

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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.

So - let's break this down. For nutrition/calorie intake: you ate a bagel before your bike (~300 calories) and then three uncrustables (570 calories) and 168 calories from your gatorade. That is 1038 calories in all. Then before the run you added another 168 calories and 24 ounces of fluid.

How long did that 75 mile bike take? I'm assuming between 3.5 and 4 hours if you were ~20mph. 24 ounces of fluid is not nearly enough for that long on the bike - you needed at least 80 ounces given the fact that you said it was humid.

To put this in perspective, last weekend I raced a 70.3. I had about 500 calories before the race (over the course of the morning) and consumed about 900 liquid calories over the course of the 3 hour bike (so now my calories were about about 1400 before I got to the run). I aim to drink AT LEAST 20 ounces of fluid an hour (some of which is my nutrition), more on hot days (this past Saturday I was definitely dehydrated after my 5.5 hour bike, and I drank about 135 ounces of fluid over that time).

You said you were dizzy and puked - that drives home that you did not fuel or drink enough.

I also rarely do anything long running wise after my long bike training days - I do run off the bike but usually just a short 25 minutes. I leave the long runs to the long run day.

Adding onto this:

Assuming 175w watts for 4hrs cycling = 2520kcal (100w for 1h=360kcal, that's a handy conversion to remember)
Running is close enough to 100kcal/mile. Both of these numbers get appreciably higher when it is hot.

Your body can hold ~2000kcal of energy in muscle/liver if fully carbed up and oxidize somewhere around 0.5g/fat/min, or 250ish kcal/hr. A simple balance says you started with 2000+300+570+168=3038kcal maximum, burned 2520 with ~1000 from fat, and set out on a run with 3038-1520=1518 kcal left. 5 miles of running gets you to 50% glycogen depletion, 10 miles down to 25%, and that's assuming you were adequately carbed up from the day before.

The math around nutrition is pretty simple, and for long distance stuff is crucial. It pays dividends to track what you eat and how your body reacts during long workouts. Based on the above info you can make educated guesses about your starting glycogen stores and fat burning rate, then make fueling decisions from there. Very generally your performance declines as your glycogen stores decline, and rapidly declines below 50%.

@Mathematics - is the 1518 correct? If you take 3038-2520 you get 518 (not 1518).

If I'm right - the math means you would have set out on the run with only 518 kcal left. Adding the 168 calories from your 24 ounces of gatorade before the run, you now have 686 calories. At 6.8 miles you were out of calories. If the glycogen depletion math works from that original 2000 calories, then at the start of the run you were already below 50% (34%) and would have declined each mile after.

I'm assuming a fat oxidation rate around 250kcal/hr for the bike portion and neglected it for the run portion since it's shorter, at a higher intensity, and the kcal/mile is so variable. It's a bit of a wildcard number since it's very dependent on intensity, training history, diet, etc. From what I've read typical values are between 150 and 350 kcal/hr. So 3038 to start, but only 1520kcal glycogen burned due to the ~1000kcal fat helping out on the bike.

Really just guessing tho, a better educated guess would include the ride's power and relative intensity. A 200wFTP rider doing 4 hrs at 150w is expected to burn through ~400kcal more glycogen than a 300wFTP rider at the same power, even though the total output is the same.

The best practice really is to take notes and after a few long workouts get a close enough value for your starting glycogen value and fat oxidation rate. Then it's just a y=mx+b graph. For a lot of people, this all becomes trivial if they can't digest the amount of fuel they need at the rate their muscles need it.