It Seemed Like Thin Air (Mash-Up)

I’ve only done this session three times, most recently February 2020. These are my notes from the workout:

Last 10 minutes at threshold very hard but finished with a good sprint. HR good, just lactic hell!

Looking at the calendar, it was a Sunday morning and I’d only done two speed session prior that week (Revolver and There Is No Try) plus a 5km run on the Friday, so I expect I was reasonably fresh. I’d also have had a big bowl of porridge pre-ride so well fuelled.

I must start putting in the workout if I eat anything but I’d think I would get through more than two gels during this session. I know the nutrition companies want to sell you more stuff but even the on the road I’ll try to get through two items (gel, bars, other snacks) an hour so perhaps more fuel is needed here?

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It is my nemesis too. For the riders it does not suit, it is a monster.Give me nine hammers any day. I try and get through 2 bottles of half strength energy drink , and will sometimes throw a gel down about 40 mins from the end

I betting the issue is fueling. I hate long indoor rides, so I usually do indoor/outdoor plans and do my long rides on the weekend outside. That means I have only ridden it once in my two years as a Sufferlandrian. I rode much of the last 30 minutes below the power targets, but I did finish. I burned almost 1500 calories on the ride according to the data. Anyone looking at the rest of the Sufferfest data on my ride would say I bonked. HR, power, cadence and speed all drop steadily after 1 hour, 50 minutes, which has to be about fueling during the ride. There was nothing in the tank at the end.
For outdoor rides over 2 hours, I use an endurance drink with some protein, as well as water, gel, electrolyte supplements, and energy bars with protein&carb mix. If I’d fueled that way for Thin Air, I might have been stronger at the end. People seem to avoid recommending fueling products, but I will recommend Hammer Nutrition. They have lots of products, none of which bother my stomach, and will happily discuss fueling over the phone for whatever endurance event you wish to undertake. Of course, there are also fueling guides in Sufferlandria, and perhaps someone who knows more, like Sir Mac or Sir Neal will comment. Best wishes.

Agreed that it’s fuelling.

Everyone’s different but I’d expect that at least doubling your gel intake will help a ton. Just eat as much as you can without getting nauseous.


I’d tend to agree on fueling although is a big workout that’s for sure. I did same workout yesterday on the reduced intensity as prescribed by my plan & still showed 1200 calories burned, so you are going to need to stay loaded up.

Just found this post in the archives

Four scoops of Roctane and shot bloks is 600 Calories. I weigh about 76 kgs.

As I recall, I could have eaten more and was hungry towards the end.

I’ve never made it through ISLTA at 100% of the “target” power but I’ve always made it through at 100% of my power. We used this one in a Knights’ event last year and only 25% managed the mythical 100%; field average was 95%. My advise is to dial it back (but only a little bit) when you start to fail and just keep going.

Thanks all. Really helpful information.

I think I might be guilty of not trying to take on too much gels as I didnt want my body to have to be working hard to digest any excess fuel and tried to be conservative on intake. maybe I went too far…

I’ll give it a go next time and double my gel intake…I’ll let you know how I get on :metal: :+1:

I’ve done this session quite a number of times at 100% and generally don’t find it too bad, but sweetspot and FTP are my forte.

Nutrition plays a big role in something this long and intense. Aim for 60g/hour of rapidly absorbed carbs (gels, sports drink).

When I was training for a very long event (15 hours, 175miles/30,000ft climb) I personally did some very hard sessions (eg 9 Hammers, HHNF etc) and then topped it off with loads of sweetspot work. I found that a great way to build endurance and I found this session to be moderately hard more than savage.


I’ve only done it once and had to turn the intensity down to 85% for the last 30 mins to get through. 2 and a half hours at 0.87 IF is really hard! I managed 0.85 IF on my effort, which is about my limit for that length of non-stop indoor ride. I was well fuelled throughout too.

Endurance is probably my thing. I enjoy ISLTA on the basis it’s long and hard all the way through.

So in addition to the fuelling advice above (and for what it’s worth I don’t use gels(ever). I find the recovery periods between the big climbs are long enough to eat a cereal bar etc s as mr to feel the effect. Maybe a gel and some solid food might help overall.)

Consider. If you are doing the workout at 100%. And then crashing out at 2 hours try the workout at 95% and see if this gives you enough in the tank to complete. Once done then this should help with the mental effect of being able to complete it. Then try knocking the %age up until you get to 100%.

It’s definitely a workout for a good day!!

This one destroyed me the first time. I wrote after the session:
“Not happy with myself on this. First session I couldn’t complete. I got in a negative headspace in the last 15 minutes and eventually my legs wouldn’t go anymore. Sucks.”

It was probably nutrition to a point, but I remember getting towards the end and thinking I couldn’t do it, wishing for it to end… I also think I switched out of erg mode a granny wheeled a bit which got me into thinking more that it’s “too hard”. I beat myself up for a few days, but the failure turned into motivation.

The session was coming up a few weeks later in my plan, and I set it as a mental goal. Got myself pumped up and excited for it weeks in advance. Planned my nutrition and did some pre-ride yoga to get ready. I felt great the second time and crushed it. For me, it was a mental game. No distractions. No background noise. Just a bigger smile as the ride went on.


Nutrition has already been mentioned numerous times, which very much appears to be a factor in this case.

However, when doing hard efforts for a long time inside, performance can be affected by insufficient cooling so make sure you do not only have fans for cheering you on.

Also consider ventilation, suffering for more than two hours will make you produce a lot of CO2, and if your room is poorly ventilated then performance may also suffer from potentially reduced oxygen levels as well.

Just some additional thoughts.


ISLTA is probably one of my all-time favorite rides. And workouts are so different for different riders, so giving my advice on this is a bit difficult.

I did ISLTA at 100% in my first training plan back in April/May and it was hard, but I did it. Somehow, I just kept pushing myself and then pushing myself, and even when it hurt I kept pushing myself… and then suddenly I was at the end. That’s usually how it feels every time. It always hurts. And it always feels hard, but it never feels like it’s going to break me. Just like I need to hang on mentally.

I love it so much I did it back-to-back at 80% for my 100km attempt and then 3 times at 75% for my 100mile attempt.

My profile is a Pursuiter, but I find I excel at and most enjoy the long sustained efforts. And somehow, this workout gives me just enough of a break at key points and never fully maxes me out and leaves me with just enough in the tank that I can just keep pushing myself over and over and over right up to the end. And then that last sprint is always epic.

I agree with the others who have commented because the first thing that jumped out at me was your nutrition. This is such a long ride that you need to keep fueling. I usually have a gel every 30 minutes starting at the 45/60 min mark along with at least 500ml of Gatorade/hour. That last 40 minute effort really demands that you have kept on top of your fueling up to that point because otherwise, if you’re low it’s too late. And on top of that, you need to mentally prepare yourself and practice your mental strength. You can do it. Only 40 more minutes. Only 30 more minutes. Spin those legs. There’s a short rest coming up. You’re under FTP so you can hold it.

Anyway, you can definitely do it!


I have had to reduce my % for a few workouts to complete them. Then try to do it at a higher % next time.

You are probably burning through ~2,000kcal during this workout so would say that if you are not fully fueled for 24 hours before getting on the bike and not fuelling it 100% during the workout you will empty your glycogen stores before the end.

I’ve made a conscious effort to train my gut to cope with fuelling as I expect to during my target event. Im now consuming ~90gm carbs per hour and the difference in RPE and performance towards the end of longer workouts is night and day.

All this talk of gels. Probably a prompt for another thread but have you thought about more of a real food fueled ride? Primal Endurance by Sisson is a suggested read.


Must admit I have never done ISLTA, so it is great getting a lot of tips here. I have never done the Shovel either, but according to my ToS prep plan I get to do both next weekend. Oh what a joyous weekend it will be!

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My nutrition advice/recipe would be:

  • Carb loading the night preceding the session (120-150g+ of pasta e.g.)
  • A well-served porridge bowl with fruits and honey in the morning
  • 1 gel every 30-40 mins
  • Gummi bears in between the gels
  • Hydration fitted to your needs with electrolytes + carbs

This way you would refill your quick absorption carbs with the gummi bears and the mid-slow absorption ones with the gels keeping your tank at bay. You are possibly running out of electrolytes, depleting your glycogen stores, and then bonking. Once bonked there is no way back.


Sounds like a solid plan! :+1:

Normally I would rely on my normal diet to take care of sufficient carbs but with the shovel the day before, it might be a good idea with some extra carbs the night before.

Usually not too fond of gels either, so might find some alternative there.