I.F. vs event duration

Is there a chart or general rule for ball parking intensity factor vs duration of event? Something like:

1hr - IF = 1.0
2hr - IF = .95
3hr - IF = .9

I’m planning on my first gravel event Saturday. 82 miles with 6200 ft of climbing. Winning time last year was 4:36. I can’t go quite that fast but think that I can be in the 5:00 range. Just curious about where IF may land.

There are a lot of factors at play, but you might be able to shoot for .8 or .85 maybe if you really nail your nutrition/hydration.

One other thing to consider is how much of a factor the draft will be. If it’s the type of race where you can get into a fast group and ride in the pack for a significant period of time, then it might be worth spending a little extra energy up front to make the selection to save yourself a bunch of time and energy later in the race.


I second the advice from @bherbers - in fact, as important as “what Intensity Factor do I want to aim for over the whole race?” is “what % of FTP can I realistically sustain on the first big climb(s) without blowing up?”

Because I guarantee that everyone will go up that first climb or two WAY harder than they can maintain the whole race. So if you shoot for 85% at the start, you’ll find yourself with much weaker riders.

As Mike Tyson said, “Everyone has a plan, until some 63 kilo machine attacks on the first climb.”


Coincidentally, I weighed in at 63.1 kilos this morning:sweat_smile:

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I was interested in the same thing and did a bit of research and experimentation last year. What I wrote at the time:

I’ve never done rides longer than 9 hours so it’s hard to determine what my target intensity should be. Hence, how fast could I cycle for the duration of this event, which is probably 11 or 12 hours.

Luckily there’s a ballpark formula: 0.95 ^ (number of hours). A 0.5 intensity would mean you do the ride at 50% of your maximum intensity so the formula basically tells that you’ll drop 5% of your intensity for every hour of racing.
This seemed a bit conservative so I decided to adjust it and use .97. Additional math told me that I should be able to sustain 220 watts on the climbs and 197 watts for the entire ride.

I was far from in a good shape at that time but I think the calculations are still quite relevant.

Full article

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+1 to this.
This has been my experience for rides around the 5 hr mark. I’ve found it leaves me pretty cooked afterwards and I’d drop it lower if I wanted to ride the day after.

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Thanks all. I hadn’t ever looked at IF before or thought of racing in that way but it came up in the most recent podcast so I started looking at some prior rides. I have a 4.5hr century last year that shows an IF of 1.03, pretty sure that just means that I hadn’t tested for awhile and FTP was actually much higher :grin:

Totally agree, I’ve been road racing all spring and I really just go with doing everything I can to stay with the lead group and I don’t really spend any time looking at power or HR anymore.

That is exactly what it means. A higher IF outside may be real when you consider the added “juice” that many of us gain when taking an FTP that came from inside testing, to riding/racing outside.

We can see higher values outside with the improved cooling and often greater motivation (to name two factors). So some delta is possible, but not to what you got in that ride. It was a low FTP.