text: excercise eventually decreases the heart rate because the heart gets better conditioned and pumps more efficiently.  Certain medications decrease the heart rate by blocking the stimulation areas of the heart (beta-blockers and calcium channel blockers).  other medicines stimulate the heart and make it beat faster.  Disease can increase the heart rate if it makes the heart have to work harder to pump the blood around, or decrease it if it's things like a heart attack (affecting the heart rate generating area, or the path of the signal) or some electrolyte distrubaces or over medication.