A medical device is configured to generate an acceleration signal and a temperature signal. The device is configured to determine an activity metric from the acceleration signal that is representative of patient physical activity. In response to determining that the activity metric is equal to or greater than a previously determined activity metric, the device is configured to adjust a target cardiac pacing rate based at least on a temperature change determined from the temperature signal. The device may include a pulse generator for generating cardiac pacing pulses based on the target cardiac pacing rate.