Exercise and fitness levels, age, body temperature, basal metabolic rate, and even a person's emotional state can all affect the heart rate. High levels of the hormones epinephrine, norepinephrine, and thyroid hormones can increase the heart rate. The levels of electrolytes including calcium, potassium, and sodium can also influence the speed and regularity of the heart rate; low blood oxygen, low blood pressure and dehydration may increase it.
exercise and fitness levels age body temperature basal metabolic rate and even a person's emotional state can all affect the heart rate high levels of the hormones epinephrine norepinephrine and thyroid hormones can increase the heart rate the levels of electrolytes including calcium potassium and sodium can also influence the speed and regularity of the heart rate; low blood oxygen low blood pressure and dehydration may increase it