What exactly does a smart trainer do?

(Frantisek Zacek) #1

Hi there,


Pretty new to Zwift but totally psyched so far…

It’s just riding the stationary trainer but *not* boring…

Even workouts which, in the end, are hardly different that if I ride those I create on my Garmin are fun since there is all that scenery, cyclists all around, the cheering messages provided by the game…


Anyways, so far I am riding on a cheap Tacx non-smart-trainer, with a HRM and a power meter in my cranks.

I am loving it even if it clearly it reaches its limits when I go into a 10% climb while in resistance 1 in 53/12 and can still spin at over 90rpm.

The fact that the game gets my speed from the weight/power/gradient makes up for that but still … it is not the same feel in the legs…

Which makes me think: smart trainer!


But I do not understand fully what a smart trainer exactly does:

  • I suppose the game *will* command the trainer to adjust resistance to have total realism regarding climbs… 

  • but how does it work in workouts? because to my knowledge, workouts *should* be agnostic of grade… is it really? and how does it adjust? since there are different ways to achieve same power all of which are fully valid (different cadences w/ different resistance)? how does it set resistance in “free” rides, for example the FTP test when one should pedal hard but with no specific power (well not exactly, but the power should be based on the feel and on previous values…)

  • I see also that the smart trainer set-up only uses the smart trainer - does that mean the power meter of the bike plays no role any longer in the game?

(Stef Levolger) #2

With a smart trainer the game in this case, or other applications, are indeed capable of adjusting the resistance on your trainer dynamically. e.g. in accordance to height profile, such as with Zwift.

In workouts it works similar on as to how for example trainerroad would work with a smart trainer, it sets a constant level of resistance. And as you change your cadence, it’ll automatically adjust the resistance to keep your power output at the set level.

For a smart trainer to work, a power meter is still required, as this gives the game the feedback on your actual power output. In many cases people will use the integrated power meter found in smart trainers. However, you may choose to use your own power meter if you desire.

(Noel Nunkovich *USMES*) #3

Just be aware that (at least for the moment) if you pair a smart trainer AND a separate power meter to Zwift the software disables Erg mode for workouts. So, since you have a crank-based power meter, if you leave it paired and add a smart trainer you’ll end up doing workouts essentially the same way you do now with your non-smart trainer: Zwift will put the trainer into Slope (fixed resistance) mode and you’ll have to match the power targets for intervals with gearing and/or cadence changes. Unfortunately, what this means is that you either have to give up the (many, for me at least) benefits of Erg mode for intervals or you’ll have to be satisfied with what’s probably a less accurate power meter in whatever smart trainer you get.

I’m really hoping this is a temporary measure and Zwift will eventually implement a feature to allow the trainer’s resistance in Erg mode to be controlled by the power numbers from a separate power meter.