I’m sure pretty much everyone, especially here at Penn State, is familiar with the discomfort of going outside and being so cold that your body involuntarily shakes. Just thinking about such icy temperatures sends a chill down my spine. But why do we shiver? Why do our teeth chatter?
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Allan Hemingway of the Department of Physiology, The Medical School, University of California at Los Angeles, California, in an APS Physiological Reviews journal, wrote an article and conducted a study about shivering. Shivering is, according to the article, a defense mechanism for when the body is endangered by cold temperatures. Our bodies are trying to protect themselves from hypothermia. It is an involuntary action that occurs with body systems and parts that people usually use intentionally, which is interesting. Oxygen intake increases when people shiver, as mentioned in another study Hemingway alludes to in the article.
Hemingway conducted a study on animals (including people) to measure their shivering in both quantitative and qualitative ways–both numerical and conceptual non-numeric ways. For example, metabolic rates were compared between neutral temperatures and exposure to cold with a shivering response. This is qualitative data. Shivering was also measured by visual cues, mechanical methods, and EMG (Electromyograms).
The study found that shivering was different from animal to animal. For examples, rabbits with thick fur coats were much less inclined to shiver at all compared to people when exposed to severe cold. There were also different temperatures at which animals started to shiver. Rats were also most likely to not shiver, but to control and warm up their bodies in alternative ways (non shivering thermogenesis).
This study is observational and likely does not suffer from the Texas Sharpshooter Problem or the File Drawer Problem.
Teens Health suggests that the hypothalamus in our brains regulates our body temperature. It signifies when we should sweat from being too hot or shiver from being too cold. By shivering, we are converting energy stored in our bodies to heat.
According to Wouter Van Marken Litchenbelt, author of Cold Exposure–an approach to increasing energy expenditure in humans in Vol 25 Issue 4 of Science & Society of Trends in Endocrinology & Metabolism, obesity is caused by more caloric intake than energy expenditure. In other words–people eat entirely more than they burn off. Someone who eats a family sized bag of chips and lays on the couch in front of the TV all day is someone who probably consumes more than they work off with exercise. There have been suggestions to implement exposure to the cold to help people to expend more energy and increase their metabolic rates. People shiver when they get too cold. The subtle shaking and jerky movements that occur from shivering help people to use up energy and generate heat. An obese person who is subjected to shivering will start to use up more energy, and possibly lose some weight!
So it seems that shivering is one of the many ways our bodies are always protecting and defending themselves. It’s cool that we have so many defense mechanisms that we don’t even have to think about in order for them to happen.