They "bend backwards" only if you look at them as a whole. They each do not but together they can make slight backward movements.

A banana takes on a slight bend as it ripens. A green, unripe banana is usually straighter.

they should hold their arms using the muscles in there back and shoulders with a slight bend in their elbows

Yes, I put a slight bend (approximately 20 degrees) to the sensor rod to insure that the tip was positioned better in the pilot light. Be sure not to crack the ceramic insulation. The result was a more reliable ignition to the burners.

Take out a hinge pin, put a slight bend in it by hitting it with a hammer, tap it back in. If it doesn't work, do the next hinge pin.