I did the second day of the first week of a 16 week training program.
This is still break in week and I had no trouble doing the routine. In fact, my average power remain higher than what is being called for. None the less, this workout was a bit more difficult than the first. My average heart rate (red line) was up by 8 bpm and my average power (yellow line) was also up by 16 watts.
I have been doing the workout without the benefit of a fan. I object to the noise and I want my body to become adjusted to the heat. However, my average heart rate increased for each interval. During my sixth and final interval, my heart rate was 11 beats higher than the first interval. I was not winded or gasping for breath, but I was breathing!