MadSci Network: Anatomy
Query:

Re: How does temperature affect muscluar activity, scientifically speaking?

Date: Mon Jul 24 23:15:16 2000
Posted By: Jeffrey Utz, M.D., Neuroscience, pediatrics, Allegheny University
Area of science: Anatomy
ID: 962240362.An
Message:

Decreasing temperature will cause muscles to have less strength and to 
contract more slowly. This is because they are made of physical molecules, 
like most other things. When they are colder, the molecules do not move as 
fast as when they are warm. In addition, nerves are colder. They do not 
conduct nerve impulses as fast. In effect, the muscles might not work as 
well as usual because the nerves are numb. Plus, the distribution of blood 
is different, which a lot blood vessels constricting, to preserve body 
heat (of course, how much depends on warm the body is, with a lot less 
vasoconstriction when the body is warm). This will also affect the way 
muscles work, especially with repeated activity, like writing the same 
thing over and over.

Finally, all of these changes will decrease the amount of coordination 
that the person has. This is because the brain is used to having nerve 
impulses travel at certain speeds; the brain is also used to feedback 
arriving from muscles at certain intervals. So one might expect that the 
effects of decreasing temperature would decrease coordination.

One must remember that the motion of writing is not just the activity of 
muscles. There is a large element of visual feedback in controlling 
activities like writing. Various types of sensory feedback, such as 
spindles in the muscles and receptors in the skin (for example, measuring 
the strength of the grip) also play a role. All of these things (except 
the visual feedback) will be affected by the changes in temperature, not 
jsut the strength of the muscles.


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