How to Train in ERG Mode

ERG mode is the most popular training mode for smart trainers, and for good reason - it automatically controls your power output so you can focus on pedaling rather than constantly adjusting resistance. Here's what you need to know about using ERG mode effectively in TrainerDay.

What ERG Mode Actually Does

In ERG mode, your smart trainer automatically adjusts resistance to maintain your target power. If you pedal faster, the trainer reduces resistance. Pedal slower, and it increases resistance. The math is simple: power = torque × cadence, so the resistance you feel (torque) = power ÷ cadence.

This means the resistance you feel at the pedals constantly changes based on your pedaling speed. Faster pedaling equals less torque, slower pedaling equals more torque. Your trainer does all the work to hit the exact power target specified in your workout.

When ERG Mode Works Best

ERG mode excels for structured workouts where you want to nail specific power targets. It's perfect for steady-state intervals, threshold work, and any workout where maintaining precise power numbers matters. I've found it especially valuable for TrainerDay users doing FTP tests or following structured training plans.

Most TrainerDay workouts default to ERG mode because it takes the guesswork out of hitting your intervals. You'll see this especially in FTP tests and structured interval sessions where precision matters.

The ERG Mode Spiral

One important thing to know about ERG mode is what we call the "ERG spiral." If you stop pedaling or your cadence drops too low, the trainer increases resistance to maintain power. This can make it harder to get going again. If this happens, shift to an easier gear or temporarily disable ERG mode to reset. In TrainerDay, you can quickly toggle ERG mode with a single tap.

Mixing ERG with Other Modes

TrainerDay lets you automatically switch between ERG, slope, and heart rate modes within a single workout. If you've done a 20-minute or 8-minute FTP test on our platform, you've experienced this - we switch in and out of ERG and slope modes depending on the interval.

You can design your own workouts that mix modes. Start with a 5-minute warm-up in ERG mode at 40-65% FTP, then switch to slope mode for some gear-shifting practice, then back to ERG for your main intervals.

Heart Rate Mode with ERG

Heart rate mode is a specific mode that automatically controls your trainer's power target (using ERG mode) based on your target heart rate. If your heart rate gets too high, it lowers your power target. Too low, and it raises the target.

This combination is especially useful for Zone 2 training sessions where heart rate tends to drift upward over time while power stays constant. Instead of manually adjusting, the trainer does it for you.

When you select HR mode in TrainerDay, ERG mode stays active - they work together. HR mode sets the target, ERG mode controls the trainer to hit that target.

Common ERG Mode Questions

Gear selection: For most efficient ERG mode training, I recommend using the small chainring and a middle rear cog. This gives your trainer the most room to adjust resistance while maintaining good chain tension.

Cadence targets: While ERG mode works at any cadence, it's most stable between 75-95 rpm. Very low or very high cadences can cause power fluctuations.

Power accuracy: For best results, do a spindown calibration of your trainer before starting, especially if you've moved it or if temperature has changed significantly.

When ERG Mode Isn't Ideal

ERG mode isn't perfect for every situation. For sprint intervals or all-out efforts where you want to see maximum power output, slope or resistance modes work better. In these cases, you want consistent resistance that lets you generate as much power as possible through higher cadence.

Some riders prefer slope mode because it better simulates outdoor riding. That's why we made it easy to mix modes in TrainerDay - use what works best for each part of your workout.

Getting Started

If you're new to ERG mode, start with a simple workout to get the feel. The trainer might seem to "fight" you at first, but that's just it maintaining your target power. Settle into a comfortable cadence and let the trainer do its job.

Remember, ERG mode is about consistent power output, not consistent resistance. Once you embrace that difference, you'll find it's an incredibly effective way to train indoors.

Most TrainerDay workouts are designed with ERG mode in mind, so you can usually just hit "Ride Now" and start pedaling. We handle all the mode switching and power control automatically.

Need help getting started? Our support team is always here to help you get the most out of your training sessions.