ROUVY ERG mode on routes: what your trainer is actually following
Ride a filmed climb inside a ROUVY workout and the gradient does nothing to your legs. That is not a fault and it is not your trainer. Inside a structured workout the trainer follows one of two things: the interval's target watts with ERG on, or a steady simulated 1% slope with ERG off [ROUVY ERG Switch]. The terrain on screen is scenery until the workout ends. Outside a workout the opposite is true, and that reversal explains almost every confused thread on this question.
By Jim Camut · Former pro & ex-Bruyneel Academy racer
Updated Sep 17, 20264 chapters7 citations
What the trainer is following, case by case
Two rules cover every case. In a structured workout ROUVY sends the segment's target watts with ERG on, or a fixed 1% slope with ERG off [ROUVY ERG Switch]. In a free ride it sends the route's real gradient, through a model built on slope, gravity, air resistance and the weight of bike and rider [ROUVY Resistance].
With ERG on inside a workout, ROUVY's description is exact: ERG mode automatically adjusts your smart trainer's resistance to match the target watts in your workout, so you do not have to shift gears or worry about pacing [ROUVY ERG Switch]. Every watt of resistance is set by the interval you are in. The road under the wheels in the video contributes nothing.
With ERG off inside the same workout, the gradient still does not come back. ROUVY's wording is the sentence the forum threads are missing: with ERG mode off, your trainer simulates a steady 1% slope, and you manage your effort manually [ROUVY ERG Switch]. A twelve-percent ramp and a flat valley road therefore feel identical. You are riding a gentle false flat either way, and the power is yours to find.
Outside a workout the rule inverts. In a normal ride ROUVY sets resistance from a model that takes in slope, gravity, air resistance and the weight of bike and rider, so the climb on screen is the climb in your legs [ROUVY Resistance]. How much of it reaches you is itself a setting: at 100% reality level the resistance matches the actual gradients of the route, and below 100% climbs get easier and the ride drops out of leaderboards and challenges [ROUVY Riding Mode].
This is why picking a route for a workout misleads. On the workout screen the route picker changes the video, not the load. A rider who chooses a mountain for a hard session gets the session they would have got on a seafront promenade, and concludes the trainer has stopped reading gradients. It has not. It was never asked to.
Why a filmed climb feels flat during intervals
Because the dose is the point of a workout, and terrain would corrupt it. ROUVY now grades that dose directly: every workout is scored on how closely you match each segment's power target, with a full star for hitting the range and none for missing it badly [ROUVY Workouts].
The scoring makes the point concrete. ROUVY rates each segment as you ride it: a full star when you hold the target power within the acceptable range, half a star when you are close but off, no star when you are far off or you skipped it, with coins awarded in proportion [ROUVY Workouts]. A route that pushed resistance around underneath a power target would be grading you on the terrain. So the terrain is removed.
That leaves the ERG toggle as a genuine training decision rather than a comfort setting, because holding one number is not the same stimulus as riding to the same average. In fifteen elite cyclists, power fluctuating by 15% around the mean every two minutes produced significantly higher oxygen uptake, heart rate and blood lactate than constant power at the same average, at both a low and a high intensity [Kolsung et al. 2020]. Variable power costs more for the same headline watts.
Read the rest of that study before concluding ERG is safer. The same authors found perceived exertion similar between the two conditions at high intensity, and called variable-power training a viable alternative there [Kolsung et al. 2020]. Neither setting is the correct one. ERG buys an exact dose and a clean score; ERG off buys a more road-like version of the same session.
Turning ERG off on purpose, and the cadence question
ROUVY names the trade itself: ERG gives precision, and switching it off gives you full control of your pacing, especially for longer efforts or when you are working on ride feel [ROUVY ERG Switch]. The button sits in the lower-right corner of the riding screen, and one click toggles it during any structured workout, so one session can mix both.
There is a physiological decision hiding inside the switch, and it is not about comfort. ERG fixes power and lets cadence float; with ERG off you fix the gear and the power floats. Power is torque multiplied by angular velocity, so the arithmetic is settled: hold 250 watts and let cadence fall from 95 rpm to 70 rpm, and every pedal stroke must produce about a third more force. Same wattage on screen, different demand on the muscle.
What that does not license is a claim about an optimal cadence. A review of nearly a century of work found that the cadence riders freely choose at low-to-moderate intensity is considerably higher, and so less economical, than the energetically optimal one, while close to maximal aerobic power the freely chosen cadence is both economical and favourable for performance, and that age, power output and road gradient all shift the choice [Hansen and Smith 2009]. There is no single right number to hand you.
Two consequences follow. Road gradient normally moves your cadence for you, and inside a workout it is not doing that, so on a long ERG interval your cadence drifts unless you watch it. Hold it steady for a mechanical reason rather than a physiological one: a trainer's control loop settles faster against a stable flywheel speed. If instead the target itself is unrideable and the trainer keeps adding resistance until you stall, that is a different failure, and our guide to ERG targets that are too hard on a KICKR covers it.
When ERG really is not working
Most reports of ERG not working are a pairing problem rather than a mode problem. ROUVY has to be able to control the trainer at all. A classic trainer cannot be connected as Controllable, which ROUVY spells out plainly: you will not automatically get resistance based on terrain [ROUVY Classic Trainers].
A classic or turbo trainer cannot be paired on its own. It needs a Bluetooth or ANT+ speed sensor or a power meter alongside it, and ROUVY then calculates virtual power from your speed and that trainer's power curve [ROUVY Classic Trainers, ROUVY Resistance]. There is no control channel, so there is no ERG and no gradient, in a workout or out of one. The fix is hardware, not a setting.
The second cause looks exactly like ERG failing and is not. ROUVY primarily searches for the power meter and it does not care about the trainer, so the power on your screen comes from the power meter whenever one is connected [ROUVY Resistance]. If your crank meter reads fifteen watts under your trainer, ERG will hold the trainer on target while the display sits stubbornly below the line for the whole interval. Nothing is broken: two instruments disagree, and ROUVY shows the one it trusts. Calibrate both, or connect one and leave the other off.
Every problem above is a rendering question: what the trainer does with a number something else already chose. AdaptCycling sits on the other side of that line. We read your ROUVY rides through ROUVY's API, estimate threshold from your power curve instead of asking you to schedule a test, and rebuild next week around what you actually completed. We do not push sessions into ROUVY today, so a workout still reaches the app by file import or one of ROUVY's own integrations. That is the argument our guide to training with ROUVY makes at length: ROUVY executes a session precisely, and something upstream still has to decide what the session is.
Quick answers
Does the route gradient change resistance during a ROUVY workout?
How do I turn ERG mode on or off in ROUVY?
Should I ride ROUVY workouts with ERG on or off?
Why is ERG mode not working on my trainer?
Does turning ERG off lower my workout score?
Sources cited in this guide
- 01
- 02
- 03
- 04
- 05
- 06Kolsung et al. 2020. Physiological Response to Cycling With Variable Versus Constant Power Output. Frontiers in Physiology.
- 07Hansen and Smith 2009. Factors affecting cadence choice during submaximal cycling and cadence influence on performance. International Journal of Sports Physiology and Performance.
More inside Training with ROUVY
Start here · Foundational guide
Training with ROUVY: a self-coached cyclist's guide
ROUVY runs structured workouts properly and decides almost nothing. What its plans cover, where they stop, and how to train around them.
Read the full guide
Other articles in this series
- 01
Are ROUVY's training plans any good?
Coach-written, four to six weeks, included in the subscription. What they do well, and the one thing they do not do after a bad week.
- 02
Training on ROUVY without a power meter
ROUVY scores training load best from power. How to train and progress on heart rate alone, and what the ledger loses when you do.
- 03
How to import a workout into ROUVY
ROUVY accepts .zwo, .erg and .mrc and nothing else. The three ways a session gets in, and why the file sometimes lands wrong.
- 04
Zwift acquired ROUVY: what changes for riders
Zwift bought ROUVY and FulGaz in April 2026. What both companies committed to, what has actually changed since, and what has not.
- 05
Which ROUVY FTP test should you take?
Ramp or twenty minutes, what each one costs you, how often to repeat it, and what to do when the number comes back lower.
Free training analysis · No card · ~3 minutes
Try the adaptive coach yourself.
Connect your rides and the coach reads your last eight weeks — intensity balance, ramp rate, what's working, what's holding you back — then drafts your training plan around it.
Free 14-day trial, no card.