Shivering occurs when many muscles contract a little bit all at once, and another response to cold is shivering. Given these facts, many muscle fibers contracting at once can be induced by among the following options:
- exposed genitalia
 - exposure to heat
 - sweating
 - exposed biceps
 - mechanical waves
 - Electrical energy
 - exposure to cold
 - Veins and arteries.


 

       exposure to cold  