incorrect CTL value?



thekgb

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Dec 14, 2007
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sorry if this comes out of my naivete, as i thought i had this down, but i'm having a mismatch in my PMC CTL score, and what i "thought" was my CTL and am not sure why. My impression was tht CTL was the daily avg TSS over 42 days. My CTL time constant is set at 42 days. When i add up the math and avg over the last 42 days i get on my calculator 55 Tss/day (which is where i had been targeting it and building my regimene around), but on my PMC it shows up as 48 tss/day? The past 6 weeks were preceeded by 2 weeks of just basically a few spins on the trainer d/t illness, and the 4 weeks prior to that not much else. i think my CTL at the start of the last 6 weeks was 36 tss/d. would those 6 weeks leading up to the last 6 weeks account for the mismatch since the starting value of CTL was so low? I have "heard" that CTL is a rolling alogrithm and extends beyond the 6 weeks in it's calculation even where it's time constant is 42 days in the PMC, but am not sure why the info i find just seems to reference the 6 weeks time period.


other info: not sure if it helps
ATL constant 7 days
TSB right now -6
ATL right now 54
the weekly TSS scores would look like a horizontal line if graphed by them selves and came from 6 weeks of 385 tss/week give or take 20 tss. it wasn't planned taht way but weather, life, etc avoided me getting in a more steady build of TSS that would have looked like a upsloping line week by week.

this fits into a larger picture b/c i am thinking that since i'm planning my training around working up to a CTL of 90 tss/day (not any time soon), and believing that all i'd have to do to get there was avg 630 tss/week over 6 weeks on a slow build. Now i'm wondering if i not only have to hit a home run (sorry for the reference) to make that goal but hit it out of the park so to speak to accomodate all the weeks prior to that 6 weeks.

any thoughts appreciated.
thanks.

Mike

ps: i've archived this and couldn't find anything that clearly specified this question that didn't reference just the 42 day interval. power411 just referenced 42 d as well.
 

acoggan

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Jul 4, 2003
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thekgb said:
i'm having a mismatch in my PMC CTL score, and what i "thought" was my CTL and am not sure why. My impression was tht CTL was the daily avg TSS over 42 days. My CTL time constant is set at 42 days. When i add up the math and avg over the last 42 days i get on my calculator 55 Tss/day (which is where i had been targeting it and building my regimene around), but on my PMC it shows up as 48 tss/day?

As described in my article to be found at www.cyclingpeakssoftware.com/power411, CTL is calculated as an exponentially-weighted moving average with a time constant of 42 d. Practically speaking, that means that what you've done during the last ~3 mo counts the most, but more recent workouts count more than those less recent...all of which explains why simply taking a straight average over the last 42 d gives you a different number.
 

thekgb

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Dec 14, 2007
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thanks for the quick response! i'll need to look a little closer into that for planning my build to goal CTL. i've heard of others using spreadsheets that they've created and will take a look into the archives for help planning around this.


much appreciated.

-Mike


acoggan said:
As described in my article to be found at www.cyclingpeakssoftware.com/power411, CTL is calculated as an exponentially-weighted moving average with a time constant of 42 d. Practically speaking, that means that what you've done during the last ~3 mo counts the most, but more recent workouts count more than those less recent...all of which explains why simply taking a straight average over the last 42 d gives you a different number.
 

daveryanwyoming

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Oct 3, 2006
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thekgb said:
...i've heard of others using spreadsheets that they've created and will take a look into the archives for help planning around this....
Mike,
if you plan to spreadsheet CTL, ATL and TSB, the key formulas are:

CTL(d) = CTL(d-1)+[TSS(d)-CTL(d-1)]*[1-exp^(-1/42)]
ATL(d) = ATL(d-1)+[TSS(d)-ATL(d-1)]*[1-exp^(-1/7)]
TSB(d) = CTL(d-1) - ATL(d-1)

which assumes a CTL time constant of 42 and ATL time constant of 7 and only one workout per day. The reference(d) refers to CTL, ATL, TSS or TSB from today, (d-1) refers to yesterday's value. If you do more than one workout per day you can either lump them together or just treat them as sucessive days.

Here's the formula that makes up the CTL column in my forward looking PMC spreadsheet in Excel speak:

=ROUND(C2+(B3-C2)*(1-EXP(-1/42)),1)

Where column C holds CTL values(seeded in row 1 and this same formula copied down with appropriate row references for all other rows), B holds daily TSS values, I'm using the default 42 day time constant and I've rounded it to a single digit for clarity. BTW folks have argued(convincingly) that it's silly to track CTL to a decimal point, just round it to whole numbers but that's the way my spreadsheet currently looks and it's consistent with the PMC in WKO+.

Hope that helps.

-Dave
 

frenchyge

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Apr 3, 2005
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Get Training Peaks WKO+, it'll help more.

More importantly, it'll give back to the folks that developed and tested all these great tools and help ensure that we continue to have great tools and methods to use in the future.
 

daveryanwyoming

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Oct 3, 2006
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frenchyge said:
Get Training Peaks WKO+, it'll help more.

More importantly, it'll give back to the folks that developed and tested all these great tools and help ensure that we continue to have great tools and methods to use in the future.
No doubt, but it's not that easy to do look ahead planning in WKO+ to plan peaks for instance or to structure future training based on TSS. Spreadsheets are still useful if you want to plan....

-Dave
 

thekgb

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Dec 14, 2007
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i already have it...and love it. it's made my training so much easier to analyze. this was more just a theoretical question when the math didn't add up to what i thought was a 42 day average.

-Mike


frenchyge said:
Get Training Peaks WKO+, it'll help more.

More importantly, it'll give back to the folks that developed and tested all these great tools and help ensure that we continue to have great tools and methods to use in the future.