I have often seen people recommending doing L4 intervals at 90% of the 20 min maximum power, and sometimes 2 or more 20 min intervals are recommended in single session and some people even claim they do these daily.
Now, this got me curious. How does 20 min max. power relate to FTP? In Andy's book, he claims that threshold power can be estimated by multiplying 20min TT power by 0.93, or 20min MP is FTP * 1.08.
Now, one's 20 min MP might be higher than 20 min TT average power, which means that 20 min MP might be even more than 108% of FTP.
I have seen some people saying that the ratio between their 20 min MP and FTP is 1.1 or even 1.2.
But if this is so, then training at 90% of 20min MP = 0.9 * FTP 1.1 = 0.99 FTP
i.e. these people would be doing their L4 intervals at 99% of their FTP.
Even worse, if the ratio is 1.2, then 90% of 20min MP = 0.9 * FTP * 1.2 = 1.08 FTP, i.e. for these people doing L4 intervals at 90% of their 20 min MP is the same as doing 108% of FTP. This is not longer L4, but L5.
Even, with Andy's estimated ratio of 0.93, we get that 90% of 20min MP = 97% of FTP which is still pretty high and can lead to over training if done daily.
So, I'm beginning to wonder the wisdom of this recommendation. To my mind it could easily lead to over training if these intervals are done daily, or on consecutive days.
It all depends on the ratio of your 20min MP and 60min TT average power (aka FTP). If this ratio is more than 1.1 then doing your intervals at 90% of 20min MP might be too much. You could get the same benefit with perhaps a little less work .
Any thoughts on this.
Now, this got me curious. How does 20 min max. power relate to FTP? In Andy's book, he claims that threshold power can be estimated by multiplying 20min TT power by 0.93, or 20min MP is FTP * 1.08.
Now, one's 20 min MP might be higher than 20 min TT average power, which means that 20 min MP might be even more than 108% of FTP.
I have seen some people saying that the ratio between their 20 min MP and FTP is 1.1 or even 1.2.
But if this is so, then training at 90% of 20min MP = 0.9 * FTP 1.1 = 0.99 FTP
i.e. these people would be doing their L4 intervals at 99% of their FTP.
Even worse, if the ratio is 1.2, then 90% of 20min MP = 0.9 * FTP * 1.2 = 1.08 FTP, i.e. for these people doing L4 intervals at 90% of their 20 min MP is the same as doing 108% of FTP. This is not longer L4, but L5.
Even, with Andy's estimated ratio of 0.93, we get that 90% of 20min MP = 97% of FTP which is still pretty high and can lead to over training if done daily.
So, I'm beginning to wonder the wisdom of this recommendation. To my mind it could easily lead to over training if these intervals are done daily, or on consecutive days.
It all depends on the ratio of your 20min MP and 60min TT average power (aka FTP). If this ratio is more than 1.1 then doing your intervals at 90% of 20min MP might be too much. You could get the same benefit with perhaps a little less work .
Any thoughts on this.