Systems and methods to monitor physiological responses to steady state activity. In an example, a physical activity signal is detected from a human or animal subject using an implantable medical device. A different, other physiological signal is also detected from the subject using the implantable medical device. The physical activity signal is processed to define first and second time periods associated with first and second steady-state physical activity levels of the subject. A first indicator is obtained by combining data from the other physiological signal obtained during the first time period. A second indicator is obtained by combining data from the other physiological signal obtained during the second time period. The first and second indicators are used to provide a resulting indicator.
