Sustainable IF over prolonged rides

TrainerRoad has an enormous set of rider data that could be used to provide insight in what intensity is sustainable over various durations, whether it be training, racing or long endurance challenges.

When planning for a 3-5 hour race, a long gran fondo (La Marmotte, Maratona Dles Dolomites), a seriously long race (Tour du Mont Blanc, Dirty Kansa) or an everesting attempt (>8,848 vertical metres), I have noticed that several members of this forum have asked for input, sharing of experiences and actual numbers (TSS and IF specifically). Regardless of your FTP, I would assume that the maximum you could achieve in such attempts can be measured in TSS or IF.

E.g., generally speaking: 100 TSS/1.00 IF is close to the maximum a rider could hold for 60 minutes, whereas a 5 minute VO2max interval may be 10 TSS/1.10 IF (per repeat), and an everesting attempt may last for 14 hours and consist of 500 TSS/0.70 IF.

I have my numbers and experiences that I base my planning on, but it would be useful if Trainerroad could provide some data based insights and recommendations here, perhaps graphically (x-axis being IF and Y-axis being duration) with the option to filter on gender, age or other dimensions (if there are significant differences). This would be very useful in two aspects:

Firstly, for planning purposes, if you know that TR data suggests than an IF of 0.85 is what is generally possible to hold for 3 hours, then you know how hard you should step on the pedal for the upcoming race without blowing up (“I see that last year I rode race X for 2:55 with an IF of 0.75, perhaps I should challenge myself to go harder this year”, or “last time I rode at an IF of 0.9 for the first 2 hours, no wonder I blew up”).

Secondly, it might be useful to indicate wether your FTP estimation is correct or should be adjusted. E.g. if you’ve ridden a 5 hour ride and managed to log an IF of 0.95, then perhaps your FTP is set too low and you are ripe for a ramp test?


I would also think they have incorporated this kind of thinking into their methodology to estimate TSS for outside rides (when no power data available) - however looking at the outcomes for TSS estimates, I think there is room to improve their methodology.

Example: I rode a race in 5:20, and selected “race pace” in the intensity drop-down for estimating TSS. It have me a TSS of 402 - which translates to an IF of 0.87 - which seems too high for a 5+ hr race.

Using an IF of 0.75 for the 5:20 seems more reasonable (?), and that gives a TSS of 300.

So yep - I agree - TR should have the data to be able to estimate (reasonably accurately) a typical/average IF for races of a given duration, and it would be a helpful reference to publish.

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@Nate_Pearson Is this something you could create and publish, based on the data you have at hand?

It’s hard because you can’t insure everyone’s FTP is accurate.


Yea using a ramp test to estimate ftp for training purposes is one thing. Extrapolating this estimate of your ftp to use for pacing long events is a fool’s errand imo. If your ftp is based on a 60 min test I’d feel a bit better about it. There is a table in the cyclist training bible iirc

I think the bigger problem is that not everyone on TR reliably measures their ftp. Some people use power meters, some use their smart trainer’s inbuild power, some use virtual power and other just type in a number manually.

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What you’re after is pretty easy to pull from your own data. You can get a lot of that info by just looking at your own power duration curve. That does not give you an intensity factor but it does show the watts you have held for all duration from 5 seconds to your longest ride.

If you want to geek out, WKO5 has a bunch of variations on the power duration curve you can use for gauging what you’re capable of on long rides and identifying weaknesses to train. One cool set recalculates your power curve to show what it looks like using data from rides after you have burned 1000 or 1500 calories. For example your max 20 minute power might be X but the max 20 minute power you’ve held after having burned 1000 calories will be less. This gives you a pretty good idea of what your sustainable power on a multi hour ride is likely to be.

@STP Thanks for the WKO tip, I will check that out! Over the years, I have quite a few rides >10 hours, so I am starting to see a pattern. The reason for my questions was more to see if there are any general experiences or insights to be had. For instance, reviewing my own data, the IF of my 12-15 hour rides fluctuates between 0.65 and 0.73. I assume that around 0.75 is the upper limit of what one can sustain for more than 10 hours, but it would be cool to test the hypothesis against a lager data set. @Nate_Pearson is right in that this is probably very difficult, and as @splash points out, data quality might not be the best - but I assume the data set can be filtered to exclude certain riders’ data, e.g. if power data is not derived from a power meter (or from power meters known to be dodgy), riders with less than X amount of cycling hours per year, riders with lower than X w/kg, etc.?

I don’t think the total of TR data is worth much on what you are after. Its so random, especially when your looking at data that is not coming directly from TR workouts that, while interesting, it is not anywhere near being scientific. There are things they can do with their data though. For example, for what you are after vis a vis longer rides TR could pull out a sample of selected riders and get data on 50 or 100 TR users who completed Iron Mans and use the bike data. Or, they could look at TR users data from popular Grand Fondos, presumably these types of riders have entered fairly accurate FTPs and we’d know the ride was at or near a max effort or at least the samples would be focus enough to use some statistics magic to clean up the data.

But, i’m pretty sure others have already done similar studies and if you look you can dig up general guidelines. For example, Best Bike Split will give you a target and from everything i’ve read, its shockingly accurate.

In the end, your own data is both going to give you YOUR target and also show you what you need to train to improve.

For sure! Just generally, too, I’m going to say we all have a problem with lying to ourselves about FTP! Ha! It is hard, hard, hard for folks to be honest about athletic performance. That’s just the way we are!

But I’m going to throw out another BIG problem with TR measured FTP and extended endurance IF for some riders: TR FTP is just something all together different than actual sustainable FTP. I can score 290+ on the TR MAP-based FTP & not be able to hold even 85% of that number for an hour.

Based on the results from my hour FTP challenge thread, this is not a problem for everybody! But it is certain sure a problem for many.

Just last night I managed 239W for about an hour and 20 minutes. During that effort I set all time HR threshold records at a little over 92% of my max HR…so a pretty good effort. But 239W is less than the what I scored on my very first TR FTP test! :roll_eyes: So for me, the TR MAP-based FTP test is measuring progress, for sure, but it’s not measuring sustained-effort progress…at least not perfectly.

For riders like that who have the idea that they’re going to go ride 100 miles at 0.8 IF…they’re going to be in for a long uncomfortable day. Some can handle that, some can’t. I’m one who can’t…either because I’m really good at producing power for a long time above threshold (which skews the results of a maximum aerobic power ramp too high) or because I’m not very good at extended aerobic efforts.


Supposedly the biggest difference between a pro and an average Joe is not w/kg but how long they can maintain a high sub threshold effort. There is a HUGE variation in that capability among the full range of cyclists so in a sense, a general statement of “you should be able to hold X intensity factor for Y hours” is basically worthless when applied to individuals.

Spot on, the longer the distance the less applicable FTP from a ramp test becomes, and the more important long rides and overall volume are. My tested FTP has been pretty stable for a couple of years now, but the power I can put out in longer distances has varied hugely depending on the volume I’m doing. E.g. I did a 100 mile race a couple of weeks ago with an IF of 0.87, but that was off the back of a lot of 10-15 hour weeks this year with long rides of at least 3-4 hours most weeks. My tested FTP is only 7 watts higher than it was 6 months ago when I was doing much lower volume (~5 hours/week), but there is no way I could have hit that IF for such a long ride on that volume.

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Another option is to use xert mapping of power similar to wko4. There is a lower threshold power model that you can ride essentially all day. For me its around upper tempo on a coggan zone setup

Yes, agree. I think the TR FTP is mostly useful for scaling TR workouts. But tbh to me the whole concept of deriving one number and the applying it to multiple situtations (climbs, flat TT, rolling TT, work at the front of a race, etc) is a bit dubious. I think its good for a ball park figure, and then you need to make your own experiences.

(That said, for me personally my TR ramp test ftp matched up quite well with what I can do in a short TT, just to contradict all that above…)

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You guys are probably right, there are perhaps too many factors at play for data to be useful for generalizations. And I suppose the best way to estimate how fast you can ride a given route/race is to base numbers on own experiences. :slight_smile:

Your IF may also depend on your style of riding. In the mountains I am able to do an IF of 0.88 for 6:45 hours (last Marmotte Pyrenees I did), something which I can never do on the flat. That’s due to being able to switch between in and out of the saddle during climbing. That’s with a CTL between 100 and 110 leading up to such an event.

0.88 IF for 6.45 hr is pretty extreme.

Are you sure you’ve set your PM to include zeros on your bike computer? Because you’ll be putting out very little power on the downhills that would require you to ride all the uphills pretty much around FTP, maybe even slightly above. That would also explain why you can’t do that on the flats where there’s much less coasting, so less zeros.

Or it could be that your outside FTP is much better than your inside FTP.


If you are using your PR graph on trainer road to calculate your best long distance IF don’t forget to use the FTP at the time of the event rather than your current.

‘Bro Science alert’. I reckon most long distance IF fir 5+ hour rides will be .7-.75 if the FTP source is correct.

The highest 20’ watts I ever recorded (indoors or outdoors) was 350W which would mean a 333 W FTP (I use a power meter for 6 years now). For this event at which my FTP was set to around 325, I managed to do 285 W normalized (including zeros) for 6:45 hours. I was placed 26th with 77 kg of body mass.
I do have an exceptional talent to keep performing at FTP levels for long periods of times, the first climb the pace is almost always too high for me and then I start to overtake people up to the finish normally. I tend to ride each climb within a minute or so of my PB during the event.


Thanks for clarifying.

That’s a remarkable performance :muscle: :biking_man: :dash: