A mobile software application may issue an alert when a user is not achieving a heath objective based on track movement of a mobile computer system that is running the application and being carried by the user and physical characteristics of the user. The software application may map information about the physical characteristics of the user to a user model and determine the energy being expended by the user based on the user model and movement information provided by the mobile computer system. The software application may determine the frequency of steps taken by the user by: bandpass filtering a time domain signal that is representative of the movement, transforming the filtered time domain signal into a frequency domain signal, and equating the step frequency with the frequency of the highest peak in the frequency domain signal.