Massive difference in effort per watts between climbing and flat

Why is this? I have climbed Alpe a bunch of times before today, but always in workout mode. When in workout mode, or on the flats, it’s not hard at all for me to hold 300 watts for an hour. Today I climbed Alpe without using training mode and I was 14 minutes slower than my best time, and I had to fight with all I had to stay above 250 watts. I suck similarly at climbing in real life. Why the huge discrepancy between my power on the flat and my power climbing? Effort is effort, right?

Hello @Timothy_Grossano and welcome to the forums!

I would think that the difference is when in sim mode (not ERG) the trainer is getting the gradient information from Zwift which causes the resistance to increase (assuming you have a smart trainer) and depending on where you have trainer difficulty set at you would be getting a much harder feel on the alp vs. during a workout. However, I seem to find it easier to put out more power in this situation, not less. So I could be way off base here…

What cadence were you averaging during the climb and what setting is trainer difficulty at?

There’s somewhat of an unknown about this in the science, it hasn’t been fully elucidated yet. There appears to be athletes who can generate more power uphill (by about 5%) and there are some athletes who cannot.

From preliminary testing I did on this 20 years ago, one thing I noted was that those who could NOT generate more power uphill were not able to climb well (within their peer group), however, for those that could generate more power it didn’t necessarily mean that they would be good climbers within their peer group.

I wasn’t able to identify anyone who generated less power uphill.

However, on Zwift even when you’re cycling uphill you’re actually not (unless you have e.g., a Tacx Magnum or similar). With something like a direct drive trainer, the resistance increases but that’s it…

Potentially, it’s something to do with muscle shortening velocities and what type of training you’ve previously done, and how long you’ve been cycling (and whether you even practice other exercise modalities such as running).

In sim mode,as the resistance cranks up, and it’s possible your cadence decreases (mine does) then the force you have to apply to the pedals increases (to maintain your power output – as power can be calculated from force applied by cadence velocity). As this force increases (which to be fair is extremely small) the feeling and fatigue change with it, as it ‘loads’ your muscles slightly differently, and may also change the ‘fuel’ that you use as you pedal (at lower cadences and the same power output a greater reliance on carbohydrates occur).

Keep training, and you will start to close the gap between the two scenarios. Good luck


Hi Ric,

Welcome to the forum. That was very informative information.

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Psssssst :shushing_face::shushing_face::shushing_face:


That was a really interesting answer, Ric. Thanks. I will start climbing Alpe 2x a week without training mode and see if I can close the power gap. Will be interesting to see if it changes my climbing outside.

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Edit: Actually, I misunderstood the question I think. But this is still a really interesting article about putting our power on the flat versus uphill.

Here’s an article I felt explained this to some extent:


I’ve not read the whole article you referenced… However, inertial loading may not be the answer…
It’s long been noted that many people produce less power indoors on the trainer versus outdoors. For many (but not all) this can be about 10% lower indoors versus out. It had been hypothesised that it was due to the inertial load being lower indoors versus outside, however, work by Edwards, et al, shows this not to be the case.

Secondly, the article you linked to makes an erroneous suggestion that at high versus low cadences you “dip into your anaerobic system”. This is incorrect. The ‘system’ you use is defined by the power output you’re producing in relation to your fitness as well as the forces that are required to turn the pedals over. At lower rather than higher cadences ‘substrate’ useage changes slightly with more energy being required from carbohydrate oxidation. This changes efficiency, and your thermodynamic efficiency increases at lower rather than higher cadences at a given power output (e.g., 60 revs/min would be more efficient than 90 revs/min).

While HR responses may (very likely) to change at higher cadences (they’ll increase) and so will your VO2 (the volume of oxygen you’re requiring to generate the energy) you’ll still be aerobic (rather than anaerobic) if you continue to ride at the same power output.

You may fatigue at a faster rate using the higher cadences (e.g., if you ride at your cruising power at 130 revs/min rather than say 90 revs/min) but this could be due, in part, to the fact that your muscles (the motor units) adapt to the joint angle and velocity at which they’re trained (so you’re changing the velocity as you pedal faster).

Hope that helps?

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I would imagine it would Timothy. I would space the efforts out over the week, as it can be brutal if you do it twice weekly, at moderate to hard levels.


I don’t think this is relevant to the question the article was addressing. It wasn’t about indoor versus outdoor, it was about flat versus uphill. For example, I find it easier to ride at 250W up a gradient than I do on flat road.

I’m not going to argue about the science or physics of it though, because I’m not qualified to have an opinion. You might well be correct in saying the article isn’t accurate, but it made sense to me.

I found a much better article that explained (at least, one version) why the flat versus uphill power phenomenon exists (and anecdotally, it does; example 1, example 2, example 3 - and GCN did a video on it ), but I can’t find it again. IIRC it was explained more in terms of kinetic energy and working against gravity, rather than physiologically.

See my post above. about flat versus uphill.

I think it was a mistake for me to include the concept of IRL climbing in this conversation. It seems to have muddied things. I’ve just noticed that in Zwift, if I’m not in training mode, that when I start “climbing”, the effort it takes to make the same watts goes up substantially. Ric’s answers were brilliant, but I do think it’s most probably a software or hardware issue.

That article was fantastic. It’s true that I definitely prefer high kinetic situations. Sparing you the details, riding on flat ground is what I always gravitate towards. Take my kinetic energy away and the way pedaling “feels” changes substantially. Zwift’s virtual resistance does a good job of simulating gravitational forces.

I really want to be a better climber. I’m going to stop using training mode and just start climbing Alpe a couple times a week.

Does zwift mark your training mode time as a pr? That would be strange right?

As someone with a wheel-on trainer with a tiny flywheel, I can tell you that I also find it easier to produce watts on the flats with a lot of wheel speed/inertia and 90+rpm (which minimizes the dead spots in your pedal stroke). On climbs, the wheel speed and cadence slows, requiring more torque or “force on the pedal” (i.e., power=torque x rpm)… and you also have that dead spot in your pedal rotation that you have to overcome, so climbing requires producing the power in a different physiological manner…which many of us find more difficult. Workout mode lets you produce the power in a manner more suited to you (with higher wheel speed and cadence, requiring less torque and easily managing the “dead spot”).


Why? A time is a time. They only last 30 days on Zwift anyway :wink:

I don’t think Strava can identify any difference, they just see a ride.

Same result today. My best time in training mode is like 48 mins. Wednesday I barely broke an hour and today I came in at just over one hour. Frankly, I find this huge gap between power uphill vs flat to be really frustrating. Really want to get performances closer together.

Honestly, why? There is a reason that there are different types of racers. Even uphill, there’s a huge difference between puncheurs and grimpeurs.

Don’t get me wrong, it’s always good to work and improve on your weak points, but obsessively “aligning” performance in different conditions doesn’t sound like a sensible goal. Before you know it you get there by becoming slower in the flats.

(That can also happen by not literally becoming slower but just not living up to your potential.)

I guess it’s because the difference is so much. And it’s not just that I’m relatively heavy. I am about 170 now. If I could push 300 watts on the climb and 300 watts on the flat and I was slower on the climb because I’m heavier than the people next to me then that would be one thing. But that’s not it. When I start going up hill (in Zwift, I’ve never used a power meter on my real bike) suddenly 300 watts “feels” as hard to produce as 400 on the flat. I just want, at the very least, my perception of 300 watts climbing in line with my perception of 300 watts on the flat.

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Just change to a lower gear so that you do the same cadence as on a flat road.

If you can’t gear lower then change the trainer difulcuty to get the exstra gear. That is why a cadence sensor and heart rate monitor is so useful.

I find it easier on climbs vs flat.