How do you decide on your IM power output based on your FT. I’ve heard a lot of theories so I wanted to get some input.
Thanks!
really? i thought there was only 1 theory.
pace it such that you don’t spend more than 260-270 TSS.
I didn’t do this very scientifically, but my IM power was 72% of my FT and I ran the entire marathon…actually earned a marathon PR by 6 minutes for my first ever IM, second ever marathon (so maybe I’m not the best source to answer this given my experience level). This was in the power range that my coach wanted me in for the race. It was tough holding back though - - I felt like I was going backwards through the field until the run portion. Then I mostly passed people and only occasionally did someone pass me.
Out of curiosity, when was your last FTP test before your race?
BikeScore or TSS is a cumulative function not an acute one day function to base a race off of.
If you don’t like the TSS methodology, then you must present an alternative. 
BikeScore or TSS is a cumulative function not an acute one day function to base a race off of.
??
You can most certainly calculate TSS (or its kissing-cousin BikeScore) for a single session, such as the cycling leg of an Ironman-distance triathlon.
+1.
Isn’t that the whole point of pacing with power?
You work backwards from what your own personal ceiling TSS is for running well off the bike, then based on an estimated bike split time, reverse calculate your target power range for the race. how else do you arrive at your target power?
The same rider certainly cannot use the same target power (as %FTP) for a 4:30 split vs a 5:00 split vs a 5:30 split, and expect to perform optimally.
At Wisconsin 2008 I rode of a 265 watt FTP (approx watts per Kilo 3.4), was my first IM and had never run a marathon before:
Stats were:
Bike split - 6:01hrs, TSS 311, I was aiming for 288 TSS on a IF of .69 but couldn’t stay in my power caps on the hills at MOO and pushed the last 10 miles into town as felt good.
Run splits were:
1st 13 - 2.04hrs
2nd 13 - 2.00hrs
never walked and my last three miles were my fastest…
In theory from what I have read 311 TSS is kinda bordering on the high side for a good run like I had which makes me think my FTP was set too low. The last two Power tests I did I was very fatigued so makes me think with a good taper my FTP may have been closer to 275…
I think that is a very good idea to estimate bike split and power.
I have data points from 3 years of training and racing so I know how fast I can go on so much power. It actually matches up quite well with analyticcycling.com power/speed calculations.
Using points from analyticcycling, I plotted my power/speed curve in excel. From that I got a formula to use to calculate any speed to power over the short speed range I’m able to ride.
With that formula, my FT, Speed, Distance and TSS calculations I’m able to produce a chart that calculates my TSS for a given distance and power. I then just follow the TSS calculation down to the range I want to ride in and I will ride that race targeting that particular power.
It’s a bit of trial and error with hilly races and I have to practice it in training but It gives me a good estimation of how hard to ride and still be able to run well afterwards.
jaretj
If you don’t like the TSS methodology, then you must present an alternative.
Why… no one has ever produced testable data in support of it (“it” being 270-300 TSS as optimal for IM bike pacing). Indeed it would be a little suprising if the TSS formula was right as it wasn’t invented for this use, and the ^2 was arrived at in non-empirical fashion.
While it’s clearly going to be the case that a standard % of FTP regardless of expected time on the bike is unlikely to be the case, I don’t think TSS is quite the right formula either, as it probably prescribed going too hard if you expect to be out for a short duration, and too easy if you expect to be out for a long duration.
The true “constant” for a IM might be something more like time x IF^4, rather than time x IF ^2
This was discussed at length last year… http://forum.slowtwitch.com/...ring=tss%20;#1872750
Note… for the sake of my sanity and time, I’m keeping out of this debate any more this time round
I was/am curious because, while you may think the theoretical underpinning of the concept is unsound, the approach has worked well for many people. I try to be open to new ways of thinking, so I just ask those who feel it is an unsound methodology to present an alternative.
+1.
Isn’t that the whole point of pacing with power?
You work backwards from what your own personal ceiling TSS is for running well off the bike, then based on an estimated bike split time, reverse calculate your target power range for the race.
Well, that is one approach that has been advocated, and there is certainly some logic to it (since TSS takes into consideration both duration and intensity). However, I was merely commenting on MarkyV’s mistaken claim that TSS (and BikeScore) are strictly cumulative functions.
+1.
Isn’t that the whole point of pacing with power?
You work backwards from what your own personal ceiling TSS is for running well off the bike, then based on an estimated bike split time, reverse calculate your target power range for the race.
Well, that is one approach that has been advocated, and there is certainly some logic to it
You’re funny, Frank…
+1.
Isn’t that the whole point of pacing with power?
You work backwards from what your own personal ceiling TSS is for running well off the bike, then based on an estimated bike split time, reverse calculate your target power range for the race.
Well, that is one approach that has been advocated, and there is certainly some logic to it
You’re funny, Frank…
I wasn’t trying to be funny: there is some logic to it. It may not have been an intended application and it may not be perfect, but it certainly isn’t illogical.