I’ve never done either, but am curious what people think is harder to complete – run a marathon (26 mi / 42 km) or bike a century (100 mi / 161 km)?
Based on your answer, how much would you have to adjust the easier event to balance them out?
I’ve done a century, but it was after I’d been riding for about 4 years. I’ve been running now for about 4 years and I still have no desire to do a marathon. I’d do a century tomorrow with a little coaxing and I haven’t been on the bike in almost a month. (End of the triathlon season and I just moved, lay off me! 
) I really dont know how I’d “equalize” them. For me, maybe 175 on the bike, maybe 150. 13.1 seems rational to me (I’ve done a half ironman). 26.2 still seems like sadism to me for some reason.
Marathon.
I dislike cycling and I’m very, very bad at it (I’m not a great runner, but I’m much better at that then cycling). But 100 miles is more annoying than anything else (if you’ve trained for it and eat for it). Certain parts of your anatomy might be a little uncomfortable, but it isn’t that bad on your body.
Running 26.2 miles beats the crap out of you. Even if you’ve trained for it.
I’ve seen 8-year-olds do double centuries on tiny little bikes with tiny little legs. Marathoning? no.
I did my first century about three months after getting a touring bike, and the only pains I had beyond the next day were from sunburn. Jogging a slow 10K, on the other hand, left me walking funny for several days afterward.
No amount of cycling is going to pound your ankles and knees like jogging will, but if I had to equate the exertion, I’d put a century ride about on par with a half-marathon.
So far I’ve only done a metric century (3 actually) on a hybrid bicycle and a 10K trail run.
I would have had little or no problem tacking on the additional 32 miles to complete a full century on my bike if it were at least somewhat flat, or at least not outrageously hilly.
After running a 10K, I briefly started training for a half marathon and stopped at the 10 mile mark. Maybe I’m just not built for running, but it’s hard on me, and I am much more sore after a long run.
In my limited experience with both running and cycling (my husband has done a few full century rides, a half-marathon, a couple of short course triathlons, and a few other events and so has more experience than I do), I’d have to say running a marathon is harder than riding a century. As far as balancing them out, hmmm. For me personally, maybe something like 260 miles on a bike is equal to 26 miles of running/jogging.
It’s a tough one for me though because I enjoy cycling and don’t really care much for running.
When I was younger & dumber, I signed up for a 350 km bicycle event - I’d do 150 km rides as training with little problem. I did marathons as well, and they took me out of commission for days.
I’ve never done a marathon but it has to be a ton harder. I’ve probably done 50 centuries, all of which were done really without any training at all. I’ve ridden a 100 miles just rolling out of bed at 11AM and deciding to do it that day. I’ve ridden 3 double centuries, and I got to admit, that was pretty hard. Even then, it was more a matter of willpower than training, although at the time I was riding a fair amount.
Now if the century is all 10% or higher grade uphill…
Brian
Then I think your blood boils and your eyes explode, because you must be on Mars.
I’m another of the ‘no comparison’ crowd - I ride a lot so saying I could do a century tomorrow doesn’t mean much, but even at my most out-of-shape, the bikes been hanging up for months I could still ride it 100 miles (slowly).
I don’t do any running at all at the moment, but have in the past, and there is no possible way I could run non-stop for 26 miles. Even with frequent stopping it seems like a tall order - just too much pounding the joints. I reckon it would take months of training just to get to the point where I could do it.
The distances are just not that comparable - runners do not regularly train at marathon distance AFAIK. Someone will correct me if I have this wrong, but if you go down to your local running club this weekend I seriously doubt you’ll see folk out for a 26 mile stretch of the legs - not as a training, we do this every weekend type-run. Most cycling clubs, OTOH, will have a century for at least one group.
I’ve done both. No contest. Marathon is harder.
Seriously, like someone said, it might be like riding up a 10% grade (maybe more like 7-8% but the point remains) for 100 miles.
Asketh CaveMike, “What is harder, a marathon or a century?”
Which is the debutante more aggressively stroking?
I’ve done century rides and half-marathons. I find the running much, much more difficult because I find it’s so demanding mechanically (on my body). The bike let’s me used gears to my advantage when I need to, so I can rely on the machine sometimes.
When I’m running, it’s all me! Oof!
I did ten marathons and only one century. Admittedly, I had not trained properly for the latter, but all things considered, I’d say the marathons are harder. Hell, anybody who gets their exercise sitting down… 
Considering when my friends and I were…what, 15, 16 or so…we rode our bikes from Brick to Jersey City and back in a day (Yahoo says that’s about 121 miles) on nothing more than a whim, I’m going to have to say a marathon is harder.
I’d say marathons are harder, having only run a few 10k’s . There are some pretty difficult centuries, though…the one I rode* wasn’t exactly a piece of cake.
*The Banana Classic. From Saratoga over the Santa Cruz Mountains to the coast, then back over the mountains again. Sheesh!
I rode my first century the day after I turned 40. I only rode one other one (the day I turned 41). I couldn’t ride one right now (14 years later), but that’s mostly because I’ve spent the last 10 years sitting in front of a computer. I did ride a metric a couple of years ago, and the worst bit was that my ass wasn’t in shape for a long ride. (You really need to build up to sitting on a bike saddle that long/that far.)
OTOH, while I MIGHT have run a mile once, I’ve certainly never run farther. I can’t imagine the effort it would take to do a marathon.
I’ve done neither. I’m the pit crew for my triathlon wife.
Many distances, many courses. She has 5 marathons under her belt. And the same for 100 mile rides (at least).
I’d say that the marathon is harder on you physically. But the bike 100 or better is harder emotionally.
The bike portion is much more stressful. And your mind still has to be very, very sharp. At 20-40 mph speeds, its easy to really, really hurt yourself.
Not so much on the run. Except maybe boredom.
The tri is -
Swim first. (You could drown)
Then bike. (You could have a bad accident, in Boulder CO 2 years ago a woman ran into a black bear that was crossing the road, she got the ‘Barely’ made it award, she finished [T-boned the bear at about 20mph])
Then run. (You could keel over and die from a medical condition of course, but at least you won’t be going to fast when it happens).
It depends on the weather, it depends on support crews, it depends on your bike and what you have trained for. It just depends.
That may be, but if you’re not toodling along, it’s not that stressful.
I’m another who’s ridden a century, and could easily do so again given a little while to get back into biking shape. A marathon? Oy oy oy!
I think it may be because when cycling (not racing), periods of effort are naturally interspersed with periods of rest. You have to pedal to get uphill, but if you’re on a slight downgrade, you can coast. And if you’re pacing yourself to do a century, you’ll take more opportunities for rest.
When you’re running, though, you have to propel yourself off the ground with every step. You can’t ever “coast.”
Another one who has done neither (yet - longest bike ride under 40mi, and I can run over 16mi but building towards marathon distance) but I’d bet the marathon is harder.
Example: The Tour de France averages about 100 mi each day for 20 days in a row. There are hundreds of participants, admittedly great athletes (leaving doping aside).
Now name all the equally-skilled distance runners who are capable of running back to back marathons over a couple of days, let alone three weeks in a row.
Not taking anything away from the riders, I just think that the marathon is much more draining.