Letting bar speed set the load
Velocity-based training uses a sensor to measure how fast the bar moves and turns that number into a programming signal. The core idea is the load-velocity relationship: for a given lift, lighter loads move faster and heavier loads move slower in a fairly predictable way. By reading today's bar speed at a given weight, a lifter can estimate whether they are stronger or more fatigued than usual and adjust the day's load accordingly.
This makes the session autoregulated, responding to readiness instead of following a fixed percentage that ignores how you actually feel.
Velocity zones and stopping on speed loss
Different speed ranges, expressed in meters per second, are loosely associated with different qualities, from heavier strength-oriented loads at slower velocities to lighter speed-strength work at faster ones. A common application is the velocity stop: ending a set once bar speed drops by a set percentage from the fastest rep, using that drop as a real-time fatigue gauge.
Exact velocity targets are lift-specific and individual, and device accuracy varies. This is general educational information rather than a prescription; thresholds should be calibrated to the lifter and equipment.