Speed/Power Inquiry?

Someone I follow on Strava recently did Getting Away With It. I did the same activity about a month ago. I’m not trying to come off as being unnecessarily competitive or comparative (if that’s the right word), but am just legitimately curious:

I have a higher average power on the activity but lower average speed. Was curious to know why?

Are you both using SYSTM’s virtual speed?

Do you have the same power/weight ratio?


I think the speed/distance will vary according to what gear you used - higher gear higher speed. It isn’t an accurate metric so I wouldn’t focus on it or try to compare if with others.


My guess is that at least one of you wasn’t using SYSTM virtual speed. When that’s turned off, speed either comes from a similar, power based calculation made by the trainer (at least for KICKRs, but only in ERG and only if it’s turned on) or is based on flywheel speed and a setting (again on the trainer) for virtual wheel size. Or, if a wheel on trainer, based on actual wheel size and speed. All of these speed measures (except SYSTM virtual speed) depend on trainer set up and, in ERG mode, gearing choices. It is the reason why speed measures for virtual rides is so inherently “fake”—they depend on what method you use to calculate it and what assumptions you make within that method.

Even with SYSTM virtual speed, differences in pedal stroke and, especially in level mode, the rider’s ability to maintain power smoothly versus big ups and downs around the target can cause average speed differences because of the way the formula deals with acceleration. But I’m not sure that could account for the size of the difference shown.


Thanks. Very well put.

SYSTM calculates speed using your weight. So with all the speed changes in the workout, the lighter person of the two of you can actually go further / faster at less power because the accelerations require less power. If it was a steady effort, the difference would be marginal - if at all noticeable.



… and of course irrelevant for training purposes. What matters is duration, HR, W, Cadence and RPE.

Doing virtual rides with others, perhaps in ZWIFT, ideally the method of calculating the fake speed and distance is somewhat realistic and equitable since this is the metric used for comparison between riders.


Sir Neal and Sir Mac have both stated that distance on an indoor trainer is irrelevent and they actually want this removed from the application as it causes situations like you just described. What is relevent? The overall effort and the range it was done in. Some other parameters that might be useful are heart rate (not range the effort should be but what actually happened as this is a primary indicator of full rest and overreaching). Cadence is one other item that should be measured as it indicates which muscle fiber types are engaged during the workout. I know this is way more than you asked, but the TL:DR is that speed and distance on a trainer are both zero.

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I agree. I display three metrics: power, cadence and heart rate. Truthfully, I don’t use heart rate to change anything about my training: it is too laggy, drifts too much on long efforts, and varies too much day to day based on other factors. I use it to provide evidence that I’m still alive after particularly painful intervals.

That said, I kinda like that SYSTM feeds distance to Strava because that allows me to accumulate things like annual mileage. While “fake”, it seems close enough for this limited purpose.


I completely agree! Unlike the Z•••• platform, which seems to over-inflate distance/speed by 20-25%, I find that SYSTM provides realistic values based on power. And I get to participate in Strava challenges, and accumulate various points/discounts (such as on Le Col, from which I purchased my Wahoo indoor cycle bibs).



I just got socks from Le Col.

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Not just inflate but over-inflate! :scream: