1. A method comprising: receiving motion data from a motion measurement device, the motion data comprising a plurality of sensor signals from a plurality of sensors in the motion measurement device, the plurality of sensor signals describing a plurality of repetitions; generating a combination signal by computing a combination of the plurality of sensor signals; generating a labeling signal by passing the combination signal through a low pass filter; generating a first order derivative signal by computing the first order derivative of the labeling signal; generating a plurality of labels based on the labeling signal and the first order derivative signal, the plurality of labels comprising: a first label that identifies a beginning of a repetition of the plurality of repetitions, a second label that identifies an extremum of a repetition of the plurality of repetitions, and a third label that identifies an end of a repetition of the plurality of repetitions; and labeling the plurality of sensor signals based on the plurality of labels.