The IF 1.0 in an hour club

0.99 in last night’s race - must try harder :roll_eyes:


Close enough right?


I also failed last night - 0.99


@KRL @jchappers @jonathanwaddell I did a WTRL event yesterday (a regular race, not the league) and got dropped pretty quickly despite averaging 300 for the first 4mins (in my very brief experience in the past 4 races I’ve been able to stay at the front at similar power). At the time it seemed like there was some crazy massive power surge, but the podium folks had very reasonable power in the B category (I averaged 3.7w/kg and ended up nearly 9 mins back by the finish). So yesterday turned into more of a tempo day for me at 0.87 (I did do 92% for the last 20mins which had Leith Hill as the finale)

Lose draft of main group and your done

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yeah, it really doesn’t take much, and of course is a common zwift physics complaint alongside the difficulty in breaking away.


I’ve done 0.97 in 1:48.

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To illustrate this and @jonathanwaddell comment, in the other cat B race the winner pulled only 3.3 wkg avg (way below the 3.9 max)

What you’ll notice from the top 7 finishers is the higher variability index than the rest of the field - the top finishers drafted drafted drafted all race and saved their energy to hammer the start, inclines and finish. They only need to do enough to not lose the draft of the front group.

Fun times…


If I understand the calculation of IF correctly, it’s going all out for an hour, a maximum effort. By that logic, you shouldn’t be able to have an IF above 1.0, and if you do, you’re underestimating your FTP in the calculation, right? More than 1.0 would mean you’re putting out more than your maximum effort, which doesn’t really work.

FTP isn’t tied to a specific duration. If you have a time to exhaustion longer than an hour you could have an IF over 1. Pros can have TTEs over 90 minutes.

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FTP is defined as your maximum power output for an hour though, and TTE is how long you can hold that power, which could potentially be more than an hour. We’re also talking about reasonably steady efforts, not a collection of sprints that can have a higher normalized power vs average power. If you can do a steady effort for an hour at higher than FTP, then you have a new FTP value to use. :man_shrugging:

It’s defined as the maximal effort you can sustain in a quasi steady state beyond which you rapidly fatigue. ‘About an hour’ comes from a single off hand comment that a 40kTt is a reasonable test for it.

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Definitetion of FTP aside (MLSS vs 1 hour power, 30-70 minutes etc etc)…

IF specifically is talking about normalized power and not average. IF = NP/FTP so it is very possible to average under FTP, normalize above that with hard efforts and end up with IF>1.0 even with a properly set FTP.

I feel like this is cheating since my FTP was set in the aerobars, whereas this zwift race yesterday was done entirely upright. 58:30 for the race itself (1.05IF, 286NP) but still managed to crack 1 for the hour with a couple mins easy spinning. I wasn’t on the limit though, so FTP upright should probably be at 290-300 based on the pulls that I was taking during the race.


Welp, time to bump FTP. This race was :banana: :banana:.