Re: Why does body temperature initially decrease with exercise?

Ok, so I take it you have told your students that body temperature rises 
after exercise, but are frustrated because you cannot show them this 
relationship. I agree with you -- body temperature does rise with 
exercise, but I believe this is the reasoning behind this phenomenon....
As I am sure you are aware, one's body is composed of a CNS (central 
nervous system) and a PNS (peripheral nervous system). The PNS is further 
divided into a sympathetic and parasympathetic nervous system. The 
sympathetic nervous system is called into action when the body is 
stressed, such as when one is anxious, or for your purposes, during 
exercise. This system is often referred to as "fight or flight." On the 
other hand, the parasympathetic nervous system is typically responsible 
for controlling body actions in the rested state, such as digestion and 
slowing of the heart, and is so called the "rest and digest" system. When 
one is excercising, the exercise is interpreted by the body as a stress, 
and therefore the body activates its sympathetic nervous system to return 
homeostasis. This system causes peripheral vaso-dilation (dilation of 
one's blood vessels in the periphery), meaning more blood is directed away 
from say the digestive system, and towards one's muscles (which need the 
increase in blood flow for its higher oxygen demand during exercise). 
Therefore, if your students felt their skin before and after excercise, it 
would be red and hot, flowing with the "extra" blood. Since your mouth is 
part of your digestive system and the sympathetic system also causes vaso-
constriction of that area, I would not be surprised if the temperature was 
a little lower there after excercise because of less blood flow. I hope 
this helps. If anything, the students will definitely begin to think about 
how the body uses its nervous system to counteract stresses and maintain 
homeostasis.