Fact 1: Shivering occurs when many muscles contract a little bit all at once.

Fact 2: Heat production is increased by shivering and non-shivering thermogenesis .

Given the two facts above, answer the question "What ccurs when many muscles contract a little bit all at once?" with the following options: 
- heat production
 - heat loss
 - sweating
 - permineralization
 - hypothermia
 - resistance
 - cramping
 - heat energy


 

 heat production        