It happened because customers went back in their cars while filling up. Experts said as you slide off your seat and go back outside, you build up a static charge, and if the nozzle is the first thing touched, the static charge can spark a fire.
So what happens if you find flames coming out of your tank? Experts said the best thing to do is keep the nozzle in the tank because the fire will go out. If you remove the nozzle though, the fire will follow the gasoline, and you, and everything around you will be badly burned.
I have found it helpful to do the stretching exercises my physical therapist recommends. Do some core strengthening exercises, such as the ones highlighted at The Mayo Clinic. By keeping your core strong, your back won't put itself in a position to cause that sciatica pain you are having.