Introduction

Automatic resistance control (also called auto-resistance, motorized resistance, or ERG-mode control) lets a bike or app change resistance for you during a workout. The feature is popular for guided studio classes, structured power workouts and immersive app rides because it produces consistent training loads and lets instructors or software enforce target power/effort automatically. This guide explains how automatic resistance works, lists the brands and best models that offer it, compares options by budget and use case, and tells you where to buy and what to check before you buy.