…Also, I wanted to add that hill running most likely is not more intense on the CNS than flat ground running because the speed of movement is slower, ground contacts are longer, and the demand for eccentric strength is significantly lower.
For me, I find this session as CNS intensive as a 6x200m@85% with same recovery. I guess it also depends on the steepness of the hill in question. I have run similar sessions on a less steep hill and felt as fresh as a daisy afterwards.
…and the fact that uphill running is more aerobically demanding than flat ground running.
That confirms why I find this particular session harder this year compared to last.