An exercise assistance system labels sensor signals received from a movement measurement device to identify repetitions within the sensor signals. The movement measurement device can transmit motion data describing the user's movement to the exercise assistance system, and includes the sensor signals generated by one or more sensors in the movement measurement device. The exercise assistance system generates a combination signal from the received sensor signals and passes the combination signal through a low pass filter to generate a labeling signal. The exercise assistance system can generate three types of labels for the labeling signal identifying different parts of repetitions. The exercise assistance system labels the sensor signals using the generated labels and can identify repetitions in the labeled sensor signals using a classification model.