[efattah]

In humans, CO2 build-up tends to inhibit shivering. For this reason, if you are on the edge of shivering, and you breathe-up for several minutes, you tend to 'get colder' and shiver more near the end of the breathe-up, due to lower CO2 levels.

One way around that (for hardcore cold water divers), is to do your recovery between dives in a high CO2 state (1-2 breaths per minute), then purge like crazy for 20 seconds before going down. I'd consider that a more advanced technique since the fast purging can be dangerous if you don't know yourself well.

I recently have been experimenting with certain foods & supplement combinations that are highly thermogenic, and cause your liver to really generate heat. This can allow a higher 'thermal gradient', meaning colder arms and legs with a core that is still warm.