A wrist-worn athletic performance monitoring system, including an analysis processor, configured to execute an activity recognition processes to recognize a sport or activity being performed by an athlete, and a sampling rate processor, configured to determine a sampling rate at which an analysis processor is to sample data from an accelerometer. The sampling rate processor may determine the sampling rate such that the analysis processor uses a low amount of electrical energy while still being able to carry out an activity classification process to classify an activity being performed.