Q When I was working as a broadcast engineer I once had the misfortune to touch a high voltage terminal in a transmitter power supply. Thank goodness I wasn’t killed outright, but the shock threw me across the room, seriously injuring my back when I slammed against the wall. To this day, I’ve wondered how the electricity was able to propel me through the air in such a fashion. Do you have the answer?
A Prepare yourself for another shock: the electricity didn’t propel you anywhere—your own muscles did! When a large electrical current runs through your body, your muscles are stimulated to contract powerfully—often much harder than they can be made to contract voluntarily.
Normally the body sets limits on the proportion of muscle fibers that can voluntarily contract at once. Extreme stress can cause the body to raise these limits, allowing greater exertion at the cost of possible injury. This is the basis of the “hysterical strength” effect that allows mothers to lift cars if their child is trapped underneath, or allows psychotics the strength to overcome several nursing attendants.
When an electric current stimulates muscles, these built-in limits don’t apply, so the contractions can be violent. The electric current typically flows into one arm, through the abdomen, and out of one or both legs, which can cause most of the muscles in the body to contract at once. The results are unpredictable, but given the strength of the leg and back muscles can often send the victims flying across the room with no voluntary action on their part. Combined with the unexpected shock of an electrocution this feels as if you are flung, rather than flinging yourself.
A common side effect of being thrown across the room by an electric shock, apart from bruising and other injuries, is muscle sprain caused by the extreme muscle contractions. This can also damage joint and connective tissue.
From QST December 2000
