Out of breath

Ok, that adjustment to my cardio workout? Totally nailed my ass to the wall. The short version- I do intervalic training on the elliptical machine. I spend a minute on the level 4, next minute 5, etc, up to 7, and return to 4. I peak at 8 at the very end. My adjustment was to spend two minutes on 7, and then two on 8 at the very end. Holy crap. I couldn't finish the full two minutes at level 8, had to stop at a minute and a half, and cool down those extra 30 seconds. I think that was the hardest cardio I've done ever. Thankfully, I have the oppportunity to do this 6 more times before Pennsic!