A medical device is configured to produce a cardiac motion signal by sampling a signal produced by an axis of a motion sensor, starting a blanking period, suspending the sampling of the signal during at least a portion of the blanking period, and restarting the sampling of the signal at the sampling frequency before the blanking period has expired. The medical device may detect a cardiac event from the cardiac motion signal and generate a pacing pulse in response to detecting the cardiac event in some examples.