Spike & CNS?

After reading some articles about overtraining on JB.com ( http://www.johnberardi.com/articles/training/what_you_dont_know_overtraining_3.htm ), I wondered on what system does Spike acts? Sympathetic or parasympathetic? Is it even related? Would it be possible to overstress while using a low dose (3 tabs per week)?
Any thoughts?

Uneducated guesses:

Caffeine-free Spike - the question does not even apply. It focuses the mind but it doesn’t “stimulate” like caffeine (doesn’t give a boost to the sympathetic system).

Regular Spike tablets - like caffeine-free Spike, plus some boost to the sympathetic system due to caffeine, yohimbine, etc.

I’ve not tested the Spike Shooters yet but based on the reports so far I would guess it gives a massive kick in the pants to the sympathetic system.

Thanks buddy, I guessed it was the sympathetic system too (well, for the caffeinated spike), but I’m still wondering if the stimulation is worth the stress? (Although I’d blindly say yes)