Watts per kg requirement comparisons during ride


(L Read) #1

Was riding close to C Obermeyer for a while today and paid close attention to WPKg for both of us. On the uphill, I kept the same wpk or slightly higher to keep pace with him. On the downhill, he was able to easily gap me using less than 2 wpk. I use a Computrainer which has built-in electronic inertia. I think most riders must be using a power meter and a fluid trainer. That instant rapid acceleration after cresting a hill must be common phenomenon with trainers that can not simulate inertia.

 Would love for Zwift to provide a designation next to the rider's name as to what equipment they are using rather than the generic lightning bolt. 

 I may consider recording the screen while I ride and post it on YOutube.

(Andy Schmidt) #2

I noticed on my ride yesterday a similar gap opening up by the rider over the top of climbs. As the descent began the other rider would quickly gap me. I use a Wahoo KICKR, so maybe the same thing is happening as with the Computrainer?


(Stewart G teamWBR) #3

I use a Computrainer as well and I always get gapped when starting the decents even if I am pushing a higher w/kg level.
I am 95kg so in reality I should be pulling away from others as most will be lighter and not struggling to keep up.


(Duane Gran [Vision]) #4

I use a CompuTrainer as well and have experienced some strain keeping up on the downhill.

That said, the w/kg is an equalizer (meaning same values yield similar pace) on an incline but it is different elsewhere:

  1. Flats: You may both be putting out around 250w, but the heavier person will have a lower w/kg ratio. The Zwift programmers may have made some assumption that heavier riders have a larger frontal area, but I’m not sure.
  2. Descent: The heavier rider should have less work to achieve the same speed, therefore a lower w/kg ratio than a light person.

The above scenarios should be independent of whatever power device used but the CT has a certain base resistance regardless of what you are doing. There is no coasting because the press on force will take you from ~40km to zero in about 10 seconds, which is not at all like the outdoors. I’m not sure what Zwift should do to compensate for it or if they should but downhill is a tad unnatural.


(Bill Verdon) #5

I have a KK Rock n Roll trainer (no power meter) and notice that the downhill speeds are a bit high…and they seem to hit quick.


(Zachariah Page EVR (B)) #6

Riding with a Computrainer (carefully calibrated prior to every Zwift ride) and was also experiencing some mismatch between my w/kg and others close to me. I am 68 kg and found on a number of cases that in order to keep up with riders in front of me that were doing around 2-3 w/kg I had to maintain between 3-4 w/kg, which I found surprising. However, I am really enjoying Zwift and look forward to many more rides with it!