I’ve noticed when doing say 3-5 intervals (of minimum 10 min in duration) at near threshold or at threshold (95-100%) I will start at relatively high cadence (100+) and notice it becomes considerably harder to hold at each progressing interval. In addition, my HR tends spike upwards as the intervals continue. My cooling is very good and I do realize that some of the HR spike could be from drift, but is this more a function of a relatively weaker aerobic system? While I like to keep my spin relatively fast at FTP and Vo2 max power outputs, I’m not opposed to varying the RPM from 85- 105. But, just curious about the physiological aspect(if any) of my question.
My second question relates to the TR step test to find FTP. Is the final minute (full completed minute) a proxy for Vo2 max power? In other words, the highest power during that test that I can hold for at least a minute, its that a proxy for 3-5minute power?