Endurance on Zwift vs. real life. Comparing two people

My partner and I have been Zwifting for a month. I am a 31 yo female weighing 62.5 kg. My partner is 55 yo female weighing 49.8 kg. In the real world she easily bests me on any bike ride- particularly on a climb or speed over long flat distance. On Zwift however it is the complete opposite. I have great success on climbs and longer rides while my partner is exhausted after a flat ride. We share the same bike and trainer. Can anyone explain this phenomenon?

Are you sure both of you have set your weight and height correctly in Zwift?

There are a lot of variables between the two of you.one of you may not feel as good on the trainer vs IRL or the opposite.
Even with 2 fans, my Zwifting is hotter than in real life.
Ultimately, Zwift is not really an outdoor simulator.

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Yes. I checked on all the settings.

Zwift does a pretty good job with just weight, height and power. But it’s having to assume everything else is even, whereas in real life there’s riding position, body shape, road craft, … The difference may lie in those things.

Or it may be motivation, even if she like Zwift you may be enjoying it more.


I do enjoy it a lot and I think I do enjoy it more than her. My theory is that IRL it’s harder for me to overcome gravity due to my extra body weight but on the trainer I am only pushing against the resistance and with my heavier weight I can put more force into the pedals.

Motivation is probably a major factor here; as is cooling, definitely need some fans blowing; the cooling aspect of riding outdoors is NOT to be overlooked inside!

It’s also worth noting, as stated in some ways; outdoor riding is extremely different, some folks naturally are more capable outdoors than indoors.

I’m personally nearing Cat A on Zwift here after starting only a few years ago; but outdoors…? A 2% incline is like torture to me (also 60kg); and the stress alone of being outside jacks up my heartrate from being what should be Zone1 power indoors, into Z3…
Actually holding power outdoors like what I can indoors? Not a chance (granted it doesn’t help I literally have nowhere to find out anyways without risking being run over), because my HR just spikes out instantly.

Zwift will certainly make you stronger; but it certainly won’t help you when it comes to what it’s like to ride outside (bike handling matters a lot; as does comfort and balance).

So potentially, what you may be experiencing outdoors is what I experience, particularly with hills/climbing; worse bike handling skills = more stress = higher HR = worse performance.

You said “same bike and trainer” but does that mean you have two bikes and two trainers, that happen to be the same brand/model? If so you should probably swap trainers and see if anything changes.


My wording was unclear. We have one bike and one trainer that we take turns on.

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In your real-world comparison, do you ride different bikes? If so, whose bike is on the trainer? I wonder if there could be bike fit issues involved.


We have three bikes total. We each have a bike for the real world and then we have an old spare road bike that we use on the trainer. If anything the trainer bike is too small for me. I intend to have us both properly fit on our real world bikes this summer as we continue to get into cycling.

it’s different inside. to keep it as simple as i can, since i will start butchering the english language if i don’t, strength is favoured over fitness indoors. i wouldn’t say it’s the complete opposite outdoors, but it’s different.

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The reason I mentioned the weight setting in Zwift is… Zwift ‘should’ account for this to some degree. In general Zwift favors raw watts on flats, but on hills it favors watts/kg, so if you and her are both going up the same hill, and her weight is much lower, you would have to push a lot more power to keep up.

If you both go to Zwift.com you can see your top power and power/weight in the “My Fitness” tab next to your feed. That would be an easy thing to go in and compare your max powers both by power and by watts/kg for various lengths to see if you notice anything off.

But that said, there are a lot of variables outside that Zwift does not account for.

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That is well said.
I will repeat that in the future.

Your partner might want to try the trainer with her outdoor bike as a comparison test. There are probably some fit differences.

Inside it’s about raw strength - while outside you really see fitness and real riding ability coming into play.

In Zwift my limit is about 1.5 hours while outside I can do a 5 hour ride (on S5 Cervelo). Even huge mountains don’t bother me outside - I’ll do 3000-4000m elevation on a single ride, but never on Zwift, way too difficult and uncomfortable.

That’s even on a kickr bike with a rocker plate.

Something else outside, I can get very low and aero on the S5 and be pretty quick on flat sections of road. Even though I’m not a very big rider, I can be fast. Maybe this is something in my benefit against Zwift.

Something else in Zwift, light riders have a harder time with the pace dynamics in big groups, outside you roll easily.

In Zwift rolling easily in big groups is deliberately prevented because they don’t want groups being able to catch breakaways too easily in races. Blame the racing crowd.


It’s unclear to me if this is a Zwift dynamics problem, or some other performance problem such as bike fit or indoor riding motivation, or a combination of those things. It would be really helpful to have power meter data from outdoor rides to understand if there is a real performance difference or if it’s just the goofy world of Zwift that causes the problem.

What are the duration of your outdoor rides Vs your Zwift rides? Often outdoor rides are a lot longer, so that might be another significant factor.

Doesn’t the preponderance of experience support a different conclusion?

Based on all the comments- I think it’s a real combination of multiple factors.