Indoor cycling glossary
Short definitions for the terms we use across reviews and guides. Built for buyers decoding product pages and trainer apps.
- ANT+
- A wireless protocol common on cycling sensors and trainers. Often more stable than Bluetooth in busy homes when the computer has an ANT+ stick.
- Bluetooth FTMS
- Fitness Machine Service profile used by many modern smart trainers to send power and accept resistance commands over Bluetooth.
- Cadence
- Pedal revolutions per minute (RPM). In ERG mode, cadence is the main lever you control while the trainer holds power.
- Cassette
- The stack of gears on a direct-drive trainer freehub. Must match your bike's drivetrain standard (or use a Zwift Cog style single cog).
- See also: Cassette and freehub guide →
- Direct-drive trainer
- A smart trainer that replaces the rear wheel. Generally more accurate and quieter than wheel-on trainers.
- See also: Best trainers 2026 →
- ERG mode
- Ergometer mode: the app sets a target wattage and the trainer changes resistance to hold it as you pedal.
- See also: ERG mode explained →
- FE-C
- Fitness Equipment Control over ANT+. Lets apps control trainer resistance (climbs, ERG, simulations).
- FTP
- Functional Threshold Power. A common training benchmark roughly describing sustainable hard power for about an hour. Many plans scale off FTP.
- Freehub body
- The part of the trainer that accepts a cassette (HG, XDR, Micro Spline, etc.). Wrong freehub means the cassette will not fit.
- See also: Cassette and freehub guide →
- Grade simulation
- How steep a climb the trainer or smart bike can simulate by adding resistance. Flagship smart bikes may also tilt the frame physically.
- Indoor training (pain cave)
- Structured or virtual riding at home on a trainer or smart bike. Consistency beats perfect weather excuses.
- See also: First pain cave setup →
- Pain cave
- Home indoor training space: trainer or smart bike, cooling, mat, and media. Built for consistency more than looks.
- See also: First pain cave setup →
- Power accuracy
- How close trainer power is to true mechanical power. Claims like ±1% or ±2% are manufacturer specs; consistency session to session matters most for training.
- Smart bike
- An all-in-one indoor bike with integrated resistance and sensors. No outdoor bike required. Flagships may add physical grade tilt.
- See also: Smart bike vs trainer →
- Smart trainer
- A trainer that both measures power (or speed/cadence) and accepts resistance control from apps over Bluetooth or ANT+.
- Spindown / calibration
- A short procedure that helps the trainer measure resistance accurately. Do after setup, moves, or big temperature changes.
- See also: Trainer setup guide →
- Sweet spot
- Training intensity roughly under threshold (often around 88-94% of FTP). Common indoor block for building fitness without full threshold pain.
- Thru-axle
- Modern bike axle standard (often 12mm). Trainers ship with adapters; measure length and thread pitch before buying.
- Virtual shifting / Zwift Cog
- Single-cog systems that shift electronically in software instead of a traditional multi-speed cassette. Popular for low-maintenance indoor setups.
- Wheel-on trainer
- Older style that presses a roller against the rear tire. Usually worse accuracy and more tire wear than direct-drive.
- Zwift
- The dominant social virtual cycling platform: group rides, races, and workouts with a large hardware ecosystem.
- See also: App comparison →
Still choosing gear? Start with the first pain cave guide or compare products.