Did You Know?
The heart rate is lower in a cold environment as compared to a hot day.
The term 'heart rate' is used to measure the number of heartbeats every minute. A normal heat rate varies anywhere between 60 and 100 beats per minute. There are several factors that affect the heart rate, the most common being exercise and noise. However, a little unknown factor that has shown to influence heart rate is temperature.
A rise in body temperature, be it from environmental factors or a medical condition, causes an increase in the heart rate. While doing a rigorous exercise routine, our body temperature increases dramatically, which is followed by a rapid heartbeat. A high-grade fever can also increase the heart rate. Simply sitting in a hot environment can also cause the heart rate to increase. So, irrespective of your physical activity, your heart may beat faster on a hot day.
Given in the paragraphs below are the reasons why and how the heart rate increases with an increase in temperature.
How Does Temperature Affect the Heart Rate
When you are roaming in the hot sun, the body temperature also increases. However, the core temperature of the body has to be maintained, despite the hot environment. Failure to control the rising body temperature may lead a to heat stroke.
It is a known fact that the amount of heat that flows out of the body is dependent on the amount of blood that circulates through the skin. So, in order to expedite heat loss from the body, the capillaries near the outermost layer of the skin dilate, causing greater amounts of blood to flow through the skin. Heat loss from the skin then occurs by convection and radiation. However, the heart has to work harder, meaning it has to pump more blood so as to improve blood circulation via the superficial skin. Hence, the heart beats faster, which actually helps to increase the rate of heat loss from the body. Also, the dilation of blood vessels lowers the blood pressure. Hence, in order to restore normal blood pressure, the heart beats faster and pushes more blood through the blood vessels.
Exactly the opposite happens when you are in a cold environment. In cold climatic conditions, it is necessary to reduce heat loss from the body, to prevent hypothermia (abnormally low body temperature). This is achieved by constricting the blood vessels of the skin. As a result, the blood circulation through the surface of the skin reduces, which contributes in lowering the heat loss via the skin. So, if you have an ice bath, expect your heart rate to slow down. In general, the heart rate drops when exposed to cold weather.
In one study, 4 people were exposed to varying temperatures for a specified duration and their heart rate responses were then evaluated. It was observed that the participants showed higher heart rates at room temperature (26 °C) than when measured at 5.5 °C. However, when the participants were asked to attend a sauna that had a controlled temperature of around 60 °C, their heart rate was still higher than observed at room temperature.
The study showed that the heart rate climbed substantially in hotter temperatures, whereas the heart rate dropped marginally in colder temperatures.
Heart Rate and External Temperature
As aforementioned, outdoor temperature plays a crucial role in influencing the heart rate. This can be gaged from the fact that the heart rate is higher while running in the afternoon as compared to running in the morning. Although, the difference is not significant (5 - 6 beats every minute), it proves how temperature affects the heart rate.
Thus, your heart rate response will vary when running during hot and cold weather conditions. So a change in outdoor temperature from 15 °C to 24 °C can cause the heart rate to increase by 2 - 4 beats every minute. Also, if the outdoor temperature jumps from 24 °C to 32 °C while running, the difference in heart rate can be around 10 beats per minute.
When you workout, the heart has the dual task of providing adequate blood supply to the muscles as well as to the capillaries of the skin in order to maintain body temperature. This activity can be a great burden to your heart if you are exercising in a hot environment. Hence, to reduce the stress on the heart, it is often advised to exercise early in the morning.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.