Hi, the Heart rate (pulse rate) of an adult should be with in range of 60-100bpm.. Sinus tachycardia(>100bpm) is usually a response to normal physiological situations, such as exercise and an increased sympathetic tone with increased cathecholamine release—stress, fright, flight, anger.... Other causes include: pain, fever, anxiety, dehydration, anemia, intake of nicotine & caffeine, & other various medical illness...