Yesterday I did 2 x 20 @ 225 watt, which is somewhat under threshold. First 20 was very easy, the second one was a lot of struggle from about 10 minutes into the intervall. Today I decided to do subthreahold intervalls @ roughly 200 watts. Made 3 x 20, with the last intervall @ 210 watt. I was suprised of the difference in stress. Yesterday I struggled with Avr HR of 160 today I had Avr HR of 145 which is what I usually have during a 3 hour ride. Could 15-25 watt really have such difference? Could it be that I am over estimating my FTP (230 watt / hour) and that 225 watts is above FTP? // Matt