Someone just sent me the following query.  My response is interpolated.  Can anyone add anything?  Does anyone know of anyone exercising until they black out?  I know fainting after endurance exercise is not uncommon, but I mean fainting on your feet while you are still exercising.

I was wondering if you could help me with something for [a TV program we are making].  I have been looking for a story of extreme strength and power in a time of need. Like a mother lifting a part of car off her child's leg or a farmer lifting a machine off himself when the necessity is there - a story of someone going beyond their limits.
 
Are these types of stories a reality or something of a fiction?

I haven't made a study of them.  I suspect they are urban myths.  Tendons would probably snap or pull off their insertions on the bone, or muscles would pull apart.  Having said that, most folks probably don't make truly maximum efforts in a laboratory setting.  In high-intensity endurance exercise, it's probably possible to exercise until you black out.  I don't know of that ever happening, but give someone the carrot of immense riches or even better the stick of death and they probably WILL exercise until they black out.  They might also manage a few percent increase in maximum force in a strength test.

I have done a study of the placebo effect on endurance performance, but all you get is 1-2%.  Others have apparently shown some decades ago that it's possible to get a new personal-best lifting performance out of some subjects by deceiving them into thinking they will be lifting less than their current personal best when in fact the weights are heavier than their current personal best.

Where do people get this type of super human strength from? Do humans have an emergency reserve or is it adrenaline?

Adrenaline wouldn't be enough to do it, and it wouldn't reach the muscles quick enough anyway for a rapid feat of strength.  It's drive from the central nervous system modulated, of course, by signals from the periphery screaming at you to stop.

Will