[Archaea]

because a person designed for running might do as well as one designed for cycling.

I believe it's easier to get fit enough to limp along for a century than it is for a marathon.

Cycling is more forgiving because you won't experience as many exercise related injuries.

Running fast will often result in injuries by virtue of the nature of the exercise itself.

That said, cycling is difficult because you force yourself into larger deficits.

Climbing in cycling is probably more difficult than simply running uphill.

Overall, a hard marathon is harder than a hard flat century.

If you added climbing to the century, at that point I wouldn't know how to compare.

A better comparison would be to ask how hard is it to get competitive in running race versus a cycling race. Both are hard and take lots of time.

However a triathlon friend of mine noted this. It will take him five months to get some running legs back, three months of cycling and two months of swimming. Take that for what it's worth.

I find it all hard, and some days I feel like a total slug, especially running. I'm running my speed work with girls right now, because I'm too slow to keep up with the track guys.