This document lists various factors that can affect heart rate, including age, gender, time of day, respiration, body temperature, environmental temperature, food intake, posture, exercise, emotions, altitude, blood volume, sinus rhythm, sinus arrhythmia, tachycardia, bradycardia, and heart block.

4.  Age
 Gender
 Diurnal variation
 Respiration
 Body Temp
 Environmental Temp
 Food intake
 Posture
 Exercise
 Emotions
 High altitude
 Changes in blood volume

13.  Sinus rhythm
 Sinus arrhythmia
 Tachycardia
 Bradycardia
 Heart block