So it's been a while since I've studied this subject, but it works as most of our needs: physical activity activates some areas of our brain (in this case mostly the parietal lobe and the cerebellum) whereas other areas have their activity reduced. What follows in our senses is a response to the increased physical demand, through tiredness and soreness. Cardiac muscles and skeletal muscles communicate with different areas of the brain (consider how fear causes your heart rate to increase, for example), which are related to different sensations.