whoawhoa said:Heart rate maybe?
Not only hr.
That wasn't the first time I was trying this one. It is 30min@ 88% FT, immediately followed by 60min@ 92%FT. Fairly simple.
I am usually able to complete the 60min. That really feels like lower L4, with fatigue building up very progressively. Typically, I seem to reach ventillatory threshold after let say 15 to 20 minutes (in the 60min). And my hr, after 10 minutes, is ~150. After 45 min, my hr is usually around 165, reaching 170 at the end of the distance.
Last sunday, I reach ventillatory threshold after 20 minutes in the first 30min (same curve as during 60min). Hr was 158. And RPE was exacly like if I had began the 60min already.
More important, I managed to do only 30min at 92%, instead of 60min. At that time (after 30min) I was already way over ventillatory threshold, almost at respiratory compensation point, hr at 170, RPE was high.
All that lead me to conclude, that during the first 30min (at .88), I was probably working higher than usual, probably at LT (at least the physiological response). That explains why it felt harder than usual, but most important, that'd explain why the first 30min of the 60min segment, actually felt like the second 30min interval of a 2X30 set.
But hey, I have nothing to prove that. Just feelings for what they are worth.
So it is not only hr, it is a combination of things. I am looking forward to understand these things better, see how they correlate and interact with each other.