Just a footnote to glenntaj's explanation of the 'needles' inserted.
These really don't hurt, just can be uncomfortable when you flex.
The 'needles' are very thin and are similar to acupuncture needles,
except that they have leads running from them, to a computer.
The other test is a shock test to 'twitch' your muscles. Kinda like putting your finger in a light socket, but of lesser intensity. If done right, just uncomfortable.
Just depends on the skill of the tester.