Which is harder, running uphill or running downhill?
I have done the Salt Lake City, Utah marathon and it has a huge chunk of descending. I think circa 5000 feet vertical the route of the year I doran it.
I was surprised how much my quads hurt from catching myself on every downhill step.
I suppose if you trained for it, it would not be so bad.
But which is actually harder? Uphill or downhill?