[chiralSPO (OP)]

I play a fair amount of speed chess online (blitz, 3 minutes per side). Although there is little physical exertion involved, I often find (especially near the end of a game, when the time is down to the wire) that my heart is racing, I am breathing hard, and sweat is dripping from my armpits.

Is this purely a result of adrenaline, or are my mental acrobatics actually increasing my metabolism substantially?

[evan_au]

are my mental acrobatics actually increasing my metabolism substantially?

Functional MRI scans show that blood vessels dilate to deliver more oxygen to parts of the brain that are more active - presumably during a chess match this would be your frontal lobes, with other parts involved in visualization and spatial reasoning.

But at the same time, unneeded areas reduce their oxygen uptake.

Overall, metabolic output of the brain remains a fairly constant (but large) fraction of your resting metabolic rate.

I would put it down to the fear of being slaughtered on the battlefield (metaphorically speaking), impending public shame, combined with mental exhaustion. This causes the surge of adrenalin of which you speak...