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Old 02-28-11, 10:09 PM
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Originally Posted by mcjimbosandwich View Post
i used to record both the GC total bike score and the PowerAgent Training stress score. They don't differ enough, and i go with the GC values as GC includes the nice graph.

Pardon me for this rather verbose explaination. TBS = total bike score = training stress score for all intents and purposes.

Stress balance = training stress balance = CTL - ATL
Long term stress = Chronic training level
Short terms stress = Acute training level

Kate, i recall you first started using power back in early January. If that's the case, GC won't be totally accurate because your starting CTL is assumed to be 0, whereas your actual CTL is probably closer to 70, given all the riding you have been doing up to that point. If you feel like playing around, go to GC and switch starting CTL to 60 or something, i bet your current CTL will rise about 10-20, thus making the stress balance more positive.

CTL is an exponentially weighed moving average with a decay time frame (i'm sure im using the wrong term here) of 42 days, with each new training stress weighed as (1-exp(-1/42))=0.024 and each the old cumulative average (CTL from the day before) weighed exp(-1/42)=0.976

Say you CTL was 85 the day before going to Bear Mountain (420TSS). Afterwards, the 420 TSS is weighed by 0.024 = 10.08 while the old value is weighed by 0.976 or 82.96. The sum of which is your new CTL = 93.04. Now lets assume your CTL is actually underestimated by 20 as you entered initial CTL of 0, now your CTL is 10.08+65*0.976 = 73.52.

On the other hand, ATL has a decay time frame of 7 days, which means it is a lot more influenced by more recent event training stresses. What this means is that your ATL will be very similar whether your CTL is 65 or 85. Obviously, if your CTL is 65 as opposed to its true value of 85, the stress balance will be more negative for 20 points.

But worry not, after 2-3 months, it won't matter what you initially put in for CTL as the older data points have an increasingly diminished weight.

Now, say that your actual CTL is 20 points higher than what GC indicates, -48.6 is still quite a negative number (most people try to stay north of -50). If i were you i'd take a rest week.
In other words, enjoy your week of being off the bike
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