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 ran 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?
Running uphill is harder...if you know how to run downhill effectively.
Running downhill requires rapid feet, and shorter than normal strides - specifically so you DON'T catch yourself. Think of a 500 pound stone falling towards your head. You wouldn't try to catch it, instead you should just try to flick it to the side (and slide your body the other way). When running downhill, this is exactly what's happening. A huge stone (the Earth) is coming at you quickly, and you can't stop it. So instead, with a quick foot movement you flick it behind you, and slide your body forward.
This takes practice, guts, and more practice! But, it's faster, and MUCH easier than over striding, slamming your heels down, and constantly trying to stop gravity from pulling you down the hill.
Don't try this for the first time in a race, especially not a trail race, as you need to learn the footwork to be safe, and to control the inevitable adrenaline rush as you realize you're one misstep away from eating it!!
Mile for mile, running uphill requires a greater amount of physical work to be performed. You are clearly working against gravity rather than with it.
However, running downhill can be perceived as more difficult for several reasons.
Running uphill will definitely exhaust you faster if you try to keep a too fast pace. On the other hand, if the hill is not too steep, it doesn't have to be much harder than running on a flat surface.
Running downhill really depends on your technique and what conditions are you running in. It will be completely different if the road is wet or otherwise slippery, as you will have to put in a lot more energy to keep your balance. But if the road is dry and you have good shoes, it can be pretty easy with some practice.
I have this 1.5km long climb on my regular jogging track, which is quite steep. I live on top of the hill, so at first I have to run down, and at the end of the track run it back up.
If I'm running it in good weather conditions, I can run down pretty fast, feeling confident that I won't slip and basically don't get tired at all. But if it is a rainy day, I take a huge care with every step, making it almost as exhausting as running back up.
The difference with running up is that it is almost always the same, no matter the weather conditions.
Running downhill is more physically demanding, as your body is doing more to resist the force of gravity.
Running uphill in itself is not more demanding unless you have a tendency to try to sprint uphill. In fact, if you close your eyes while running uphill, you can easily convince yourself that you are running on a flat plane.
Actually, if one goes uphill and downhill at "constant velocity", the work done by the muscles is identical in both cases. You can verify this by stepping up a single stair "very slowly" with one leg, and then lowering yourself back down "very slowly". You've expended the same amount of energy (work) going up as coming down. The difference in running downhill is that you are more in "free fall" between steps and your joints absorb more of the force in decelerating than your muscles, so less work is done by your muscles.
