Abstract: A system for measuring weight-lifting performance is described. The system comprises a collar that may be attached to a weight bar, wherein the collar comprises at least one motion sensor, at least one touch sensor, and a signal processor. The motion sensors comprise a barometric altimeter, a gyroscope, and/or an accelerometer that measure the motion of the weight bar during a lifting activity. Signals from the motion sensors are interpreted by the signal processor as physical activity data, which are then wirelessly transmitted to a multimedia device having a data processor. The data processor is configured to calculate performance metrics from the physical activity data and to display them to a user via a display on the multimedia device. Athletes may use the performance metric outputs from the data processor to monitor the form of their lifting exercises for training purposes, safety considerations, and self-improvement.