I say screw the strava climbing stats and just hammer the flats!! Do you really want to look like the guy below just to place better on strava?

Watts are watts. Physiologically, an equivalent power output will be equivalently draining. And that's why power meters are useful training tools.

Psychologically though, it can vary.

It's hard for me to reconcile that with the understanding that muscle fiber recruitment depends on the speed and force of contraction and that different types fatigue at different rates.

I think you're overthinking this. Power is the product of speed and force, but if we are talking about the same power, it's just the same power. 250w is 250w whether you're going 20mph on a flat road or 10mph up a hill. And 250w is 250w whether you're in a big gear mashing or a small gear spinning.

But you don't address the question of muscle recruitment. Physiologically, mashing and spinning will recruit different proportions of Type I and II fibers, so it would appear they are not equivalent physiologically. We know the two types don't fatigue equally, but I don't know what "draining" means.

My wife rides as fast as i do on flats. I destroy her on the climbs. we are the same size. she works less hard than i do on flats, i work less hard on hills, very odd, but we have muscles built for diff things i guess. bike of course play some roll.

No, I'm not into Strava.

It is entirely worthwhile for climbing performance.

Dropping another five pounds to Janez Brajokvic's weight should knock about 100 seconds off my Mt. Diablo hill climb coming up in October. Might even be worth giving up beer entirely until then.

How are you measuring how hard each of you work? If you weight the same & you are faster up the hills on the same day on similar equipment you are working harder.

You're right. They are different, but the main difference to me is the stress that mashing puts on my knees.

Standing up frequently is less efficient so more tiring to get the same power output. That's why it's generally best to stay seated in the climbs. I know el pistolero would argue otherwise but he's a mutant.

B does not follow from A. ~60 rpm is more efficient than 80-100 rpm, but most people find the higher cadence less fatiguing.

I am not measuring, only observing. I know I have to work hard to keep up with her on flats. she (seems) to have no trouble maintaining her cadence. Then we get to hills. partially, my bike may be better designed for hills, hers for flats, partially i may be a better or more intuitive shifter and can transfer my power more efficiently into the hill, and maybe we are built different, and for some reason I climb faster. I certainly have more upper body strength, so that may play into the climbing. My posture on the bike is also different. so many factors. I find it all very interesting, because I don;t think they are the same thing, climbing and flats, they are so very different, and some are better than others at one or both.

I suppose everyone is different and some cyclists are more/less efficient at different cadence, sit vs. stand.

It's "conventional wisdom" that standing gives more power but less efficient, but of course YMMV.

Everyone is different but but not that different. Everyone tested was more efficient around 60 rpm than they were at the higher cadences. Maybe the focus should stay on fatigue rather than efficiency since the two are pretty much unrelated.

did a state championship road race a few years ago, thinking i could climb decently (having raced a few seasons already)...made it over the first small climb barely hanging onto the pack, and blew up spectacularly on the BIG climb that came up next. Chagrined, i decided to attack all the climbs on the group rides as hard as i could for the next couple of months, and was surprised to make gains fairly quickly. A big part of it was physiological (thinking i had to pace myself more than i really did), but definitely gained some fitness too. By the end of the summer I was in the top 3 up the more competitive climbs in a group of cat 3 and 4 racers.

being scared of cracking has been the biggest thing for me to overcome as a racer, and realizing that if i do crack, nothing really that bad happens, was the biggest difference. the brain is a powerful thing when directed correctly.

Power is power no matter how it is exerted, but that's not the question, it's a physiological one. Probably the muscles are used differently in a climb, versus on the flats. Doing the same wattage with your tongue as with your legs would indeed be a very big difference.

I tend to favor the first position as a practical matter. I'm sure differences in cadence, and position in climbing versus riding on the flats do make some difference, but for practical purposes it still comes back to watts are pretty much watts whether its 300 watts up an 8% grade at 9mph, or 25mph on the flats.

In training in Florida, for mountainous races such as Everest Challenge, I've found that long intervals aimed at raising FTP, done on flat ground are pretty effective training for climbing, because its all about w/kg.

Admittedly training on the flats for climbing is not perfect, because there are some muscle recruitment issues, as well psychological issues, but it translates pretty well.

Two largest potential differences in how your muscles are used: 1) Cadence; this is addressable through gearing;
2) different position; Because your front wheel is tilted up, your bend at the waste tends to be more significant climbing; you can address this on the flats by riding deep in the drops.

So depending on gearing and position the muscles you're using don't have to be that different climbing from riding on the flats.

Since the relative position of the contact points is unchanged by rotation (i.e., bars, saddle, and pedals are in the same relative position climbing as on the flat) any change in body position is entirely the choice of the rider. There is nothing enforcing a different position for climbing and level riding.

More tiring on the flats for the same power because of lower positioning.

Agreed. I trained for the Mt. Diablo Challenge one year almost exclusively on flat roads. Lots of 2x20' and 6x5' intervals. I would ride them into the prevailing wind, use a big gear, and sit up on the tops or hoods to mimic my climbing position.

Tiring as in draining energy? The same in the end. As in fatiguing of the muscles used? Depends on conditioning. Which is why I think taking a breather on a difficult climb I find it easy to get going again - and sometimes I do even better after a short break because it's not a matter of lacking energy yet. But after a long, fast ride, more food and drink are essential to getting going again.

Does anyone (aside from Drew Eckhardt, who gets it, but confusingly uses the term "inertial load") look at their Powertap data? If you do, you'll see something called Torque, which is what y'all are skirting around.

Torque measures force on the pedals, and you'll see it's possible to derive the same watts at the hub at varying torque levels (mostly related to cadence). Obviously, generating more force on the pedals, as when climbing, should be more fatiguing than generating less force on the pedals, as one could choose to do making a given wattage on the flat.

We all know that turning a higher RPM allows us to put out power more efficiently, and that's because of torque. We can do 250w at 85rpm and 7.6nm, or 250w at 75rpm at 8.5nm, the latter representing more effort for the same watts.

Which weights more: one pound of feathers or one pound of lead?

Torque has nothing to do with inertial load, and if you find the term confusing, I would suggest reading some more on racing and training with a power meter. It has been discussed at length. Here's a starting point. Quadrant Analysis | TrainingPeaks

It's hard to follow your reasoning when you say everyone knows higher rpms are more efficient when data from every test shows just the opposite to be true. ~60 rpm is most efficient with efficiency dropping for higher and lower rpm's.