How to ride a trainer (ERG) workout outdoors

In ERG mode the trainer holds the power for you. You pedal, the resistance adjusts, and the target is hit whatever gear you’re in. Take the same workout outside and all of that becomes your job, on a road that keeps changing. This guide covers how to pace without ERG, where each kind of block belongs, what to do at stops, and when to adjust the targets.

What ERG was doing for you

ERG mode sets the trainer’s resistance so your power matches the target. If your cadence drops, resistance rises, and the watts stay the same. Transitions take only a few seconds. There’s no gradient, no wind, no coasting and no traffic.

Outside, the power you need depends on your speed, the gradient, the wind, the surface and the weight of you and the bike. You control it with cadence and shifting, and the terrain is always moving it. Expect it to be noisier, and judge each block by its average rather than second by second.

One interval ridden indoors in ERG mode and outdoors, with its target bandIndoors, ERGOutdoorstarget bandinterval average
Indoors, ERG holds the power flat on the target. Outdoors, the same interval moves around the band with every rise and gust, and you judge it by its average.

Before the ride: read the workout as a list of blocks

Write the workout down: warm-up, each work interval, each recovery, cool-down. Then sort the work intervals by what they need:

  • Long, steady blocks (sweet spot, threshold, 10 minutes and up) need a climb that lasts as long as the block, or a long flat road with no junctions.
  • Short, hard efforts (VO2 max, 3 to 8 minutes) fit on smaller climbs and rises, where the gradient keeps the load on.
  • Micro-intervals like 30/15s are the hardest to move outdoors. They need a steady road where you can switch between on and off without braking.
  • Recoveries, warm-up and cool-down can go anywhere, so put descents, junctions and towns there.

The guide to planning a route for interval training shows how to fit those blocks onto a real route by hand.

Pacing without ERG

Start each interval in control. The first seconds of an interval outdoors often come out too high. Aim for the target, not above it.

Show a smoothed power figure (3-second or 10-second) rather than instant power, and the lap or interval average next to it. Change gear before the gradient changes, not after. On a climb, a slightly lower cadence than indoors is normal. On the flat, shift up early so you’re not spinning out.

If you have no power meter, use heart rate for long blocks and perceived effort for short ones. Heart rate takes a minute or more to catch up with a hard effort, so in a 3-minute interval it’s mostly showing you the past.

Stops, lights and junctions

Plan them into the recoveries where you can. When one lands in an effort anyway, decide in advance what you’ll do. A stop of a few seconds: carry on and accept the dip. A longer stop early in a long block: restart and add the lost time at the end. A stop in the last minute: count the interval as done.

Time-based steps keep running while you wait at a light. If your head unit’s steps end by distance instead of time, the step stays tied to the road and waits with you, though the interval then lasts as long as it takes you to cover that distance.

Adjusting targets for terrain

A few adjustments are normal outdoors:

  • Climbs: many riders put out a little more power uphill than on the flat. Hold the target and don’t let the climb push you over it.
  • Flats and tailwinds: high power on the flat means high speed. A sustained effort into a headwind comes at a lower speed, which can make it easier to control.
  • Descents: on anything steep, power drops to near zero whatever you do. Keep descents out of work intervals.
  • Recoveries: treat the recovery target as a maximum. Riding below it is fine. Riding above it because a road happens to tilt up is not.

Let the route do what ERG did

Gritmaps takes the workout you’d ride indoors, imported as a .fit file, from Garmin Connect or Intervals.icu, or picked from the built-in library, and finds a route where the terrain sets the load: climbs under the long efforts, unbroken flats for the steady ones, descents and junctions in the recoveries. To fit the road, interval durations flex within strict limits, with hard efforts kept close and the warm-up, recoveries and cool-down taking up the slack. Power targets are never changed.

The adapted workout goes to your Garmin or Wahoo with each step ending at a distance along the route, so the changes happen where the terrain changes. Generating routes is free, and sending to your device is part of Premium, free during the beta. Create your free account and take your next trainer session outside.

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