I’m trying to get my head round this W’ thing
On the workout header I’ve somehow got my W’ set at 10300. Is that Joules?
Only last workout my W’ drop was 11.1 kJs.
Could somebody explain to me what it means and is it any use to me?
Yes, the value is joules (watt * seconds).
There are a number of threads discussing this, if you search using “prime”.
https://forum.intervals.icu/search?q=prime
The highnorth website explains it quite well.
lets say your actual (not estimated) W’ is 10kJ (= 10,000 joules or watt seconds) and your FTP is 250W.
How long can you go at 325W?
-
Figure out wattage over ftp:
325-250 = 75W over ftp -
Figure out how long
10,000 watt seconds / 75 watts over ftp
= 133 seconds
Answer is you can go 2 minutes and 13 seconds.
What if your W’ was 11.1kJ? Then you could go 148 seconds or 2 min and 28 seconds (11,100/75) at 325W if your ftp is 250W.
What if you pushed W’ up to 15kJ? At an ftp of 250W, you could hold 325W for 200 seconds or 3 minutes and 20 seconds.
An accurate W’ and FTP/CP can also help you optimize high-intensity intervals.
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So is to simplictic to say that my W’ isn’t 10.3 kJs and is a minimum of 11.1kjs on the assumption that my ftp is correct?
Hard to say without looking at your data. Also it can be really hard to do all-out efforts at say 3 minutes, 5-6 minutes, and 12-14 minutes in order to estimate CP/FTP and W’.
Bonus points if you can throw in a 4th all-out effort 20-30 minutes. You really need 3 solid all-out efforts and look at a special curve to see how good of an estimate. With a 4th effort over 20 minutes my ftp and cp are basically the same.
Personally my W’ moves slowly if at all. I generally use 17kJ and ftp varies from 220 to 270. With that W’ my all-out short efforts and up +/- 0kJ on the W’ timeline.
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