Glossary — terms around rocker plates, smart trainers & eCycling

The most important terms that recur on kellersprinter.de — alphabetical. Looking for something specific? Ctrl+F (or ⌘+F).

Ball pressure: The internal pressure of the inflatable rubber balls used as lateral damping in a rocker plate. Lower pressure = more out-of-the-saddle motion, higher pressure = more stable position. Reference values depending on training kilometers: 0.08 to 0.30 bar.
BFU100: Standard for birch plywood / phenolic film panels with phenolic resin bonding (EN 636-3s). Weather- and moisture-resistant, dimensionally stable — the standard choice for the body plates of a rocker plate.
Bottom-out: State in which a damping element (e.g. the rubber ball) uses its full travel and "bottoms out". On a rocker plate, bottom-out occurs when ball pressure is too low or the rider is heavy/very dynamic.
Core / core stability: Stability of the trunk muscles (abdominals, lower back extensors, obliques). On a rocker plate, the required ball pressure depends heavily on core stability — a well-trained core allows considerably softer pressure. More in the core training guide.
eCycling / eRacing: Virtual cycling in software worlds (Zwift, Rouvy, MyWhoosh, etc.). The smart trainer automatically adjusts resistance to match the gradient in the virtual world. eRacing = the competitive variant with live opponents.
ERG mode: Operating mode of a smart trainer in which the app sets a target wattage and the trainer adjusts resistance automatically — independent of cadence or gear. Ideal for structured interval workouts.
FTP — Functional Threshold Power: The average wattage you can sustain for one hour. Standard reference for defining training zones. Indoor FTP is for many athletes 5–15% lower than outdoor FTP — reasons: lack of cooling, restricted motion, different muscular activation.
Rubber isolator / vibration isolator: Cylindrical (type C) or conical (type CT) natural rubber elements that act as the rotation axis between bottom and top plate of a rocker plate. On kellersprinter.de, type C 50×50 mm M10×10 with Shore A 55 is recommended as the standard, with CT 50×50 M10 NR 56 as an alternative for more travel.
Natural rubber (NR): Elastomer made from the sap of the rubber tree. Behaves progressively: soft initial spring rate, hardening end stop. Preferred for vibration isolators on rocker plates because the return behavior feels more natural than SBR.
Perineum: Anatomical region between the sit bones and the anus, through which the pudendal nerve (Nervus pudendus) runs, among other structures. While seated cycling, a large share of body weight rests on this area; sustained high pressure and shear loads can lead to numbness, pain and functional disorders.
Pudendal nerve: Main nerve of the pelvis. Provides motor and sensory supply to the perineum, genital and anal region. Sustained pressure (e.g. through static indoor cycling on a hard saddle without motion) can lead to pudendal neuropathy with numbness or pain.
Rebound: Return behavior of a damping element after load. High rebound = the ball pushes back fast and forcefully (can feel "nervous"). Low rebound = quieter, more damped return to neutral.
Rocker plate: Movable platform under the smart trainer that allows lateral out-of-the-saddle motion and aims to reproduce the on-the-road feel in an indoor setup. Typical build: bottom and top plate of plywood, several rubber isolators between them as a rotation/pivot axis, and air- or rubber balls placed on the sides as damping. The exact number and arrangement of isolators and balls varies by build (e.g. compact boards vs. continuous XXL platforms).
SBR — styrene-butadiene rubber: Synthetic elastomer. Harder and more linear than natural rubber, less progressive. On rocker plates more commonly found at hardness 70 — on kellersprinter.de, natural rubber Shore 55 is preferred.
Shore hardness: Measure of indentation resistance of elastomers. Shore A 55 = medium-soft, Shore A 70 = harder. Lower values = more compliance and travel on the rocker plate.
Smart trainer: Trainer with electronically controlled resistance and Bluetooth/ANT+ connectivity. Broadcasts watts, cadence and speed, accepts control commands from eCycling apps. Examples: Wahoo Kickr, Tacx Neo, Elite Direto.
SprintBoard: Proper name of the rocker plate design developed by KellerSprinter for smart trainers and smart bikes. The SprintBoard S, with three elastic rubber isolators, is the compact, especially dynamic variant for road bikes paired with a smart trainer. The larger SprintBoard XL, with five rubber isolators on a continuous platform, has proven itself mainly for smart bikes. Today the SprintBoard S is the standard, while the XL is used specifically for smart-bike setups.
Out-of-the-saddle / standing effort: Standing pedaling out of the saddle, typical on climbs or sprints. On a rocker plate the standing effort feels much more natural because the bike can sway sideways — like on the road.

Missing a term? Drop me a short email: info@kellersprinter.de.