Re: does water affect heart pusle rate?

Your question is a bit vague, so I'll interpret it a bit.

1) if your question is whether swimming in water affects your heart rate, the answer is yes. We have a "diver's reflex," a vagal response, that occurs when the nerve endings of our face, mouth and pharynx experience cooler temperatures, as when we immerse ourselves in water cooler than skin temperature. One effect of the vagal response is to lower the heart rate (make the heart beat more slowly). If you ever see a doctor on TV dunk a patient's face in a bucket (or place ice on the face) because the patient is having an arrhythmia, the vagal response is their intended effect. The writers of medical TV shows seem to love this effect; I've seen it several times. As well, taking a large breath and holding it as we most often do when swimming can temporarily lower the heart rate.

2) if your question is whether drinking water affects your heart rate, the answer is a little complicated. Many, many factors impact the heart's rate of beating; one of these factors is blood volume. In order to maintain a more constant total flow of blood, the heart beats faster if there is less blood volume in the vascular system. In a patient with depleted blood volume (from blood loss or dehydration due to sweating, fever, poor fluid intake, etc.), drinking water will replete blood volume and reduce the heart rate. On top of that, actually swallowing cold fluids can produce the vagal response I noted in the explanation above about swimming.

I hope this answers your question.

Tim Nicholls, MD
Berkeley, CA