The "Shock" that Robin is referring to is the same whether it is between the probes or from the device. Taser original called their effect "Electro-Muscular Disruption" (not sure if they still do, I took my last full instructor course quite a while back....) is an effect generated by wattage of the electricity which overrides the signals from the brain to the effected muscles (which are at a lower wattage). The problem that he is alluding to is that when the two points of contact are very close (probes, or the contacts at the front of the device) then the amount of muscle effected is obviously small. You can use muscles in other parts of the body just fine, if you can overcome the psychological and pain effects of the device. While this is becoming more and more of a factor for Law Enforcement (dealing with repeat offenders, criminals realizing it isn't a wonder-tool, criminals expecting the Taser beforehand, etc) it should be less likely for a supposedly unarmed person who draws and fires on a threat who did not 100% know ahead of time that they were about to be "tased". So, if you have the probes spread out along most of your back, it dramatically affects what you can do. If the probes at 4 inches apart after a close shot (the lower probe shoots our at a slight downward angle, so spread increases with distances from the device) you still would not get much "EMD".
When I was shot in the chest, about 1/5th of a second before the picture was taken in the above post, my torso caved and I fell, but I broke my fall with one of my hands/arms (which you can see on the other stills and the video). After about 4-5 seconds I also look up over my shoulder for the clown who was supposed to shut the C2 off after 5 seconds to make sure that he was on the ball.... it felt like at least 10.... that was the first time I was shot in the chest and the first time with the new XP Probes, which are supposed to up the perceived force.
The various models (there have been at least 4 significantly different models of modern Tasers, plus the variations of color, cameras, lasers, etc) have different stats and some of what Taser has put out in the instructor courses has changed over the years, so be sure to watch the training DVD that Taser puts out with any of the models or seek qualified training (note that Taser does not have ANY official training program in place for civilian customers, except the print & DVD materials that accompany the devices) before trusting the numbers you see on the net.
-RJP