Systems and methods select accelerometer data to store on computer-readable media. Systems may comprise an accelerometer, a processor, and a computer-readable medium storing instructions executed by the processor. Accelerometer data from a critical time period are stored on a computer readable medium if an activity ratio for the critical time period exceeds an activity threshold. The numerator of the activity ratio comprises a count of data windows in the critical time period that satisfy one or more count criteria and the denominator comprises the total number of data windows in the critical time period.