ERG Mode and Resistance Mode Differences Explained

Indoor training has transformed how cyclists prepare for the season, but the choice between ERG mode and resistance mode remains confusing for many riders. Understanding when to use each mode can make the difference between productive training sessions and frustrating workouts that leave you questioning your fitness.

How ERG Mode Works

ERG mode, short for ergometer mode, maintains a target power output regardless of your cadence or gear selection. When your smart trainer is locked into ERG mode at 200 watts, it will adjust resistance automatically to keep you at exactly 200 watts whether you’re spinning at 70 RPM or 100 RPM.

The technology works by constantly monitoring your power output and making micro-adjustments to resistance. Pedal faster, and the trainer reduces resistance. Slow down, and resistance increases to compensate. This creates a unique training environment where you cannot escape the prescribed wattage through gear changes or cadence shifts.

For structured interval training, this means you can focus entirely on maintaining cadence and form rather than constantly checking your power meter to ensure you’re hitting the target. The trainer does the work of keeping you in the zone.

How Resistance Mode Works

Resistance mode simulates outdoor riding by allowing you to control power output through gear selection and cadence, just like climbing a real hill. The trainer provides a fixed resistance level or simulates gradient, but you determine the actual wattage by how hard you pedal.

In a virtual environment like Zwift, resistance mode adjusts to terrain. Hit a 6% grade, and you feel it through increased resistance. Descend, and resistance drops. You shift gears and modulate effort exactly as you would outside, which preserves the natural rhythm of outdoor cycling.

This mode requires more active engagement. You must monitor your power and adjust gearing or cadence to maintain target zones during intervals. It’s less automatic than ERG mode but more closely mirrors real-world cycling dynamics.

When to Use ERG Mode

ERG mode excels for steady-state interval training. Sweet spot intervals, threshold efforts, and endurance rides at specific wattages become straightforward. Set the target, maintain your preferred cadence, and the trainer locks you into the prescribed effort.

FTP tests benefit enormously from ERG mode. During a 20-minute test, you can set the target power and focus on pacing and form rather than constantly adjusting gears to maintain wattage. This reduces variables and often produces more accurate results.

Beginners find ERG mode particularly valuable because it removes the complexity of power-based training. Rather than learning to match power targets through feel and gear selection, new riders simply maintain a comfortable cadence while the trainer handles the rest.

Polarized training plans with long Zone 2 rides also benefit from ERG mode. Locking in 65% of FTP for 90 minutes removes the temptation to drift into Zone 3, which defeats the purpose of easy aerobic development.

When to Use Resistance Mode

Sprint intervals demand resistance mode. ERG mode cannot adjust quickly enough to accommodate the rapid power changes in a 15-second all-out effort. You’ll hit the “spiral of death” where the trainer cranks resistance so high you cannot maintain cadence, causing power to collapse.

Race simulations require resistance mode to replicate the dynamic nature of pack riding. In a criterium or group ride scenario, you need to surge, recover, shift, and respond to attacks. ERG mode’s fixed power output eliminates these critical training adaptations.

Cadence drills work better in resistance mode. Practicing high-cadence spinning at 110-120 RPM in ERG mode feels unnatural because resistance drops to near zero. In resistance mode, you can select appropriate gearing and develop neuromuscular coordination at high cadences with meaningful resistance.

Over-under intervals, which alternate between just below and just above threshold, can frustrate in ERG mode. The constant resistance changes as you shift between power targets can disrupt rhythm. Many riders prefer controlling these efforts manually in resistance mode.

The ERG Mode Spiral of Death

The most common ERG mode problem occurs when cadence drops during hard efforts. As you fatigue and RPMs fall, the trainer increases resistance to maintain target power. Higher resistance further reduces cadence, triggering more resistance. This feedback loop ends with you grinding at 40 RPM against massive resistance, unable to recover.

Preventing the spiral requires maintaining cadence discipline. If you feel RPMs dropping during an interval, shift to an easier gear immediately. ERG mode doesn’t care what gear you’re in, so drop down before cadence collapse becomes inevitable.

Some riders avoid ERG mode entirely for intervals above threshold because the margin for cadence error shrinks. At VO2 max wattages, a small cadence drop can trigger the spiral faster than you can respond. For these efforts, resistance mode provides more control.

Practical Recommendations

Use ERG mode for your bread-and-butter training: sweet spot intervals, tempo rides, endurance sessions, and FTP tests. These workouts benefit from the simplicity and precision ERG mode provides. You’ll complete higher-quality intervals because you’re not distracted by power fluctuations.

Switch to resistance mode for anything explosive or highly variable. Sprints, race simulations, over-unders, and group rides on virtual platforms all feel more natural with manual control. You’ll develop better power modulation skills that transfer to outdoor riding.

Consider hybrid approaches for specific workouts. Some training platforms allow you to use ERG mode during intervals and resistance mode during recovery periods. This combines the precision of ERG intervals with the natural feel of self-paced recovery.

Pay attention to cadence in ERG mode. If your natural cadence is 85 RPM, don’t try to grind intervals at 70 RPM just because ERG mode allows it. Maintain your outdoor cadence patterns to preserve pedaling efficiency and reduce injury risk.

Experiment with both modes to understand your preferences. Some riders thrive on the mental simplicity of ERG mode and complete harder workouts as a result. Others find resistance mode more engaging and sustainable for long indoor sessions. Neither mode is universally superior; the best choice depends on the workout and your psychology.

For riders training with power outdoors, spending some time in resistance mode indoors helps maintain the skill of hitting power targets through gear selection and cadence control. ERG mode is a training tool, not a replacement for learning to regulate effort manually.

The ultimate goal is using indoor training to improve outdoor performance. ERG mode delivers highly controlled physiological adaptations. Resistance mode develops power modulation skills and race-specific fitness. A well-designed training plan incorporates both, using each mode where it provides maximum benefit.