I’m new to using the Kickr Core 2 with Zwift. I’ve done a lot of outdoor cycling and use a Garmin Rally 200 power meter. My FTP is currently around 200 W.
Yesterday, I completed a 90-minute outdoor ride with an average power of 161 W and an average heart rate of 129 bpm. However, when I recently attempted a 60-minute indoor interval session on Zwift (4x5-minute intervals), I had to stop early — and the intervals were capped at just 150 W, which felt surprisingly intense.
I’ve read in forums that indoor training can often feel harder than outdoor riding (and I haven’t used a fan yet), but I’m still wondering: is this level of difference really normal? Or could there be an issue with my indoor setup?
I’d appreciate any tips or insights. Thanks in advance!
If there’s a difference between the power numbers coming from your pedals vs the indoor trainer, you can dual-record an indoor ride to quantify the difference. I can’t guess whether you will see a difference or not.
You could also pair the pedals as your power meter in Zwift.
You could also use the ANT+ power meter control feature in the trainer so it prefers the data coming from the pedals.
You could also do an FTP test indoors and use that number to set workout intensity, or use an estimated FTP value from a 3rd party app like intervals.icu that you calculate from indoor ride data, excluding outdoor data.
It can be because you aren’t getting any rest, outside you coast at times, eg coming up to junctions or when having to slow down around pedestrians walking, etc.
For a real comparison you’d want to ride on a velodrome where there are no interruptions and a smooth surface or go and ride up a big hill (eg, Col de la Bonette).
Thanks a lot for your helpful hints. Regarding your remarks:
I already compared my built-in power meter with my power meter pedals, and there was hardly any difference. So I suppose that, at least for now, riding indoors simply feels more demanding.
Unfortunately, I don’t have the chance to test in a velodrome (unless you meant a virtual one in Zwift?). Outdoors, however, I have a steady standard route with long, uninterrupted sections, and I can clearly confirm: there is a noticeable difference compared to indoors.
My fan arrived today, and it definitely improved things, though the feeling is still not the same as riding outside. I’ll keep testing. I also ordered a rocker plate today, which will hopefully make the setup smoother as well.
One more question: so far, I have only tried a few custom workouts. At 160 watts, I’m around 1.8 W/kg (190 W at 90 kg). From what I’ve observed, about 90–95% of the other riders are far above my level. That surprises me, because outdoors I’m not among the slowest. Is this simply because Zwift attracts so many highly ambitious riders? Or should I just cut my listed weight in half?
If you put all of your ride data into intervals.icu, it will tell you how your power numbers compare to other riders your age.
In Zwift you also have a lot of people with inaccurate trainers, spin bikes, that sort of thing. Their power is often over-estimated. I suspect that the population on intervals.icu is more based on actual cyclists who ride bicycles and own power meters. That might give you a better idea of how you compare to other people more like you, if you’re curious about that.
you weight a little less than me, but my FTP is around 300 watts. I don’t consider myself a “highly trained” cyclist, but I’ve been riding and racing regularly for the past 8 years or so. In Zwift category terms I’m at the higher end of C and lower end of B category.
How many hours a week are you riding and training? I average around 6 - 8 hours a week. How long have you been cycling (serious or targeted training)?
Compared to whom? I’m not the fastest either, but if I’m in a group of people who average 15 mph outside I’d certainly be labeled as the fastest guy in the group. It all depends on who you are comparing yourself too.
If you aren’t used to exercising near your threshold heart rate, suddenly doing a bike race or workout where your heart rate is at let’s say ~160bpm (everyone is different, i used to be comfortable at 175bpm until a few years ago, now ~155bpm for a 10-20min effort is pretty close to my limit) instead of your 129bpm ride can feel weird.
And even if you were confident in your power FTP ability from outdoors was a maximal effort, the chances are you wouldn’t get close to that indoors until you adapt to the heat, which will probably take at least two weeks of frequent indoor riding.
If you’re new to FTP testing, the chances are you will improve simply with practice, especially if you’re trying to judge what you can manage over approx 20mins.
I am a hobby driver which has been quite out of shape and now for around 1 year doing around 5-8 hours per week. Until 1 Month ago I simply went out and tried to get to my limit (this was around 31km/h on a one hour ride flat route; BPM was around 170 then). Since a month I let ChatGPT do my training planning with GA1/GA2, Sweetspot, HIIT and so on due to the fact that I didn’t progress with my own stupid training as I wanted to.
My FTP was guessed by ChatGPT with my training data. Should I do a new FTP-Test within Zwift? And do I understand it right, that I just go as far as possible in this FTP-Test to figure the right number out?
start with the ramp test as that is better for beginners who aren’t used to pacing an all out 20 minute effort. The ramp test will give you a good enough number, usually slightly over estimated, but that is ok for now. You don’t stop on the ramp test until you are fully exhausted and can no longer pedal, it will be a max effort.
It offers several different ways to estimate FTP from the data you give it, and you can link Zwift to it so it will pull in future rides. I had a lot of ride data in Garmin Connect so I exported years of data from there and uploaded it to get started.
eFTP says 198 Watt. This is quite on point to what ChatGPT guessed. Will do the ramp FTP on Zwift tomorrow to see where it brings me. I would suppose its lower…
FTP Ramp Test: I arrived at 280 Watt, but completed only 260 Watt. So the result was 195Watt for my FTP. nearly the same as ChatGPT guessed from my outdoor trainings.
Interestingly my FTP wasn’t updated in profile. Do not know if this should be the case.
Yes it should update the in-game profile that you see in the examples here:
But you can always adjust it yourself to whatever you think is appropriate, and if workouts are too hard you can also use the bias adjustment to reduce a power target if you need to.
Thanks! The interesting thing is that FTP outdoor and indoor seems to be the same although if feels totally different. But I think its quite normal then and I have to live with it…
Are you getting sufficient cooling? That’s another thing that will make hard workouts feel impossibly hard. More fans, chilled drinks, etc. Cardiac drift is exacerbated by higher core temperature, and that’s often a problem when riding indoors. That would also show up as higher heart rate at the same power level as you are doing outdoors, assuming you ride long enough and hard enough.
Just quoting myself here. Indeed BPM is a lot higher on same Watts. Since the last two trainings I have a fan and it seems to get better. Probably I have to just get used to things.
