I think it means to be sharply motivated. Does that sound right to you?

Ejerciciar isn't a recognized word, per the RAE, but a few people apparently use it. They probably meant ejercitar (to exercise).
I think your phrase should contain ejercer, though. This verb means to practice, as in to practice law, to exert, and to exercise a right. When this verb is followed by the preposition de, it means to practice as or to behave/act as.

I think this last meaning is what was meant.

Espoleta is either a fuse (of a bomb) or a wishbone. I think they are using the first meaning.

So, I believe ejercer de espoleta means to act, or behave like a fuse - someone who, or something that triggers a reaction or sets something in motion.

Did you hear it or see it in writing somewhere poli?

Did you hear it or see it in writing somewhere poli?
It was from a newspaper article. Unfortunately, I cannot find the article
now. Rusty is right about ejercer. I spelled the infinitive incorrectly. I think the phrase means take the plunge, go for it. El Pais is really simple to read except in the Opiniones y Cultura sections. It's there that you'll find interesting writing and unusual dichos.

I found the article (http://www.elpais.com/articulo/revista/agosto/espantada/majestades/elpepirdv/20080727elpepirdv_7/Tes/), and after reading it a couple of times, I'd venture a guess that it means "to backfire":

Pero los cambios introducidos por el nuevo patrón de EMI, Guy Hands, quien el año pasado pagó más de 5.000 millones de euros para integrarlo en su conglomerado Terra Firma, han acabado por ejercer de espoleta.The changes spearheaded by Guy Hands, EMI's new CEO ... have ended up backfiring.

But that's just a guess. Another option: "have caused a chain reaction".

As Rusty says, it must mean literally "to set off the bomb", "to trigger the fuse", etc.

Edit: Here's another option: "to pull the plug", "to pull the pin" (as in a grenade)

This phrase may be common in Spanish journalism, because I got it from another article (perhaps written by the same journalist). Setting off a bomb is good, but getting the ball rolling seemed to work in the article I read. Too bad Sosia is on vacation. He might know. Anyway, I dont think we'll be using this phrase in daily conversation.

It would be nice to get a native speaker's opinion on this, preferable someone from Spain.

Never I have heard the sentence Ejerciciar de espoleta, in really I don't that meaning it.

Never seen it b4 :)

Ejerciciar is not recognisable.

Changed the thread title from ejerciciar to ejercer.

Rusty's right
Ejercer de espoleta: "To work as a trigger" "To work as a bomb's fuse"

espoleta(Etim. disc.).
1. f. Aparato que se coloca en la boquilla o en el culote de las bombas, granadas o torpedos, y sirve para dar fuego a su carga.


Pero los cambios introducidos por el nuevo patrón de EMI, Guy Hands, quien el año pasado pagó más de 5.000 millones de euros para integrarlo en su conglomerado Terra Firma, han acabado por ejercer de espoleta.
The changes acted as a trigger and the problem exploded.

Saludos :D

Never I have heard the sentence Ejerciciar de espoleta, in really I don't that meaning it.

I have never heard of the sentence "Ejerciciar de espoleta." I don't know the meaning of it.

Correction :) :)

Una persona causa que otros se animen a hacer algo / anima a otros a hacer algo.
Una cosa trae consigo otra cosa.

I can think of 'hacer de detonador'
Or just 'detonar'

Dunno, gatillos y espoletas are too technical for everyday usage

I'm sure that's what it means : to act as a detonator
or being a catalyst. The phrase can be used either to covey
a good or bad thing.

I continue without understand the mean of Espoleta or the another thing, please someone could to be lovely of explain me, What does espoleta mean?

Because I seem a sightless without know the mean of the phrase Espoleta.

Espoleta es el pestillo pequeñito que esta por ejemplo, colgando de la parte superior de una granada. Si tocas la espoleta, la bomba estallará.

Espoleta y gatillo